注塑模具英文文献
塑料注塑模具中英文对照外文翻译文献
外文翻译及原文(文档含英文原文和中文翻译)【原文一】CONCURRENT DESIGN OF PLASTICS INJECTION MOULDS AbstractThe plastic product manufacturing industry has been growing rapidly in recent years. One of the most popular processes for making plastic parts is injection moulding. The design of injection mould is critically important to product quality and efficient product processing.Mould-making companies, who wish to maintain the competitive edge, desire to shorten both design and manufacturing leading times of the by applying a systematic mould design process. The mould industry is an important support industry during the product development process, serving as an important link between the product designer and manufacturer. Product development has changed from the traditional serial process of design, followed by manufacture, to a more organized concurrent process where design and manufacture are considered at a very early stage of design. The concept of concurrent engineering (CE) is no longer new and yet it is still applicable and relevant in today’s manuf acturing environment. Team working spirit, management involvement, total design process and integration of IT tools are still the essence of CE. The application of The CE process to the design of an injection process involves the simultaneous consideration of plastic part design, mould design and injection moulding machine selection, production scheduling and cost as early as possible in the design stage.This paper presents the basic structure of an injection mould design. The basis of this system arises from an analysis of the injection mould design process for mould design companies. This injection mould design system covers both the mould design process and mould knowledge management. Finally the principle of concurrent engineering process is outlined and then its principle is applied to the design of a plastic injection mould.Keywords :Plastic injection mould design, Concurrent engineering, Computer aided engineering, Moulding conditions, Plastic injection moulding, Flow simulation1.IntroductionInjection moulds are always expensive to make, unfortunately without a mould it can not be possible ho have a moulded product. Every mould maker has his/her own approach to design a mould and there are many different ways of designing and building a mould. Surely one of the most critical parameters to be considered in the design stage of the mould is the number of cavities, methods of injection, types of runners, methods of gating, methods of ejection, capacity and features of the injection moulding machines. Mould cost, mould quality and cost of mould product are inseparableIn today’s completive environment, computer aided mould filling simulation packages can accurately predict the fill patterns of any part. This allows for quick simulations of gate placements and helps finding the optimal location. Engineers can perform moulding trials on the computer before the part design is completed. Process engineers can systematically predict a design and process window, and can obtain information about the cumulative effect of the process variables that influence part performance, cost, and appearance.2.Injection MouldingInjection moulding is one of the most effective ways to bring out the best in plastics. It is universally used to make complex, finished parts, often in a single step, economically, precisely and with little waste. Mass production of plastic parts mostly utilizes moulds. The manufacturing process and involving moulds must be designed after passing through the appearance evaluation and the structure optimization of the product design. Designers face a hugenumber of options when they create injection-moulded components. Concurrent engineering requires an engineer to consider the manufacturing process of the designed product in the development phase. A good design of the product is unable to go to the market if its manufacturing process is impossible or too expensive. Integration of process simulation, rapid prototyping and manufacturing can reduce the risk associated with moving from CAD to CAM and further enhance the validity of the product development.3. Importance of Computer Aided Injection Mould DesignThe injection moulding design task can be highly complex. Computer Aided Engineering (CAE) analysis tools provide enormous advantages of enabling design engineers to consider virtually and part, mould and injection parameters without the real use of any manufacturing and time. The possibility of trying alternative designs or concepts on the computer screen gives the engineers the opportunity to eliminate potential problems before beginning the real production. Moreover, in virtual environment, designers can quickly and easily asses the sensitivity of specific moulding parameters on the quality and manufacturability of the final product. All theseCAE tools enable all these analysis to be completed in a meter of days or even hours, rather than weeks or months needed for the real experimental trial and error cycles. As CAE is used in the early design of part, mould and moulding parameters, the cost savings are substantial not only because of best functioning part and time savings but also the shortens the time needed to launch the product to the market.The need to meet set tolerances of plastic part ties in to all aspects of the moulding process, including part size and shape, resin chemical structure, the fillers used, mould cavity layout, gating, mould cooling and the release mechanisms used. Given this complexity, designers often use computer design tools, such as finite element analysis (FEA) and mould filling analysis (MFA), to reduce development time and cost. FEA determines strain, stress and deflection in a part by dividing the structure into small elements where these parameters can be well defined. MFA evaluates gate position and size to optimize resin flow. It also defines placement of weld lines, areas of excessive stress, and how wall and rib thickness affect flow. Other finite element design tools include mould cooling analysis for temperature distribution, and cycle time and shrinkage analysis for dimensional control and prediction of frozen stress and warpage.The CAE analysis of compression moulded parts is shown in Figure 1. The analysis cycle starts with the creation of a CAD model and a finite element mesh of the mould cavity. After the injection conditions are specified, mould filling, fiber orientation, curing and thermal history, shrinkage and warpage can be simulated. The material properties calculated by the simulation can be used to model the structural behaviour of the part. If required, part design, gate location and processing conditions can be modified in the computer until an acceptable part is obtained. After the analysis is finished an optimized part can be produced with reduced weldline (known also knitline), optimized strength, controlled temperatures and curing, minimized shrinkage and warpage.Machining of the moulds was formerly done manually, with a toolmaker checking each cut. This process became more automated with the growth and widespread use of computer numerically controlled or CNC machining centres. Setup time has also been significantly reduced through the use of special software capable of generating cutter paths directly from a CAD data file. Spindle speeds as high as 100,000 rpm provide further advances in high speed machining. Cutting materials have demonstrated phenomenal performance without the use of any cutting/coolant fluid whatsoever. As a result, the process of machining complex cores and cavities has been accelerated. It is good news that the time it takes to generate a mould is constantly being reduced. The bad news, on the other hand, is that even with all these advances, designing and manufacturing of the mould can still take a long time and can be extremely expensive.Figure 1 CAE analysis of injection moulded partsMany company executives now realize how vital it is to deploy new products to market rapidly. New products are the key to corporate prosperity. They drive corporate revenues, market shares, bottom lines and share prices. A company able to launch good quality products with reasonable prices ahead of their competition not only realizes 100% of the market before rival products arrive but also tends to maintain a dominant position for a few years even after competitive products have finally been announced (Smith, 1991). For most products, these two advantages are dramatic. Rapid product development is now a key aspect of competitive success. Figure 2 shows that only 3–7% of the product mix from the average industrial or electronics company is less than 5 years old. For companies in the top quartile, the number increases to 15–25%. For world-class firms, it is 60–80% (Thompson, 1996). The best companies continuously develop new products. AtHewlett-Packard, over 80% of the profits result from products less than 2 years old! (Neel, 1997)Figure 2. Importance of new product (Jacobs, 2000)With the advances in computer technology and artificial intelligence, efforts have been directed to reduce the cost and lead time in the design and manufacture of an injection mould. Injection mould design has been the main area of interest since it is a complex process involving several sub-designs related to various components of the mould, each requiring expert knowledge and experience. Lee et. al. (1997) proposed a systematic methodology and knowledge base for injection mould design in a concurrent engineering environment.4.Concurrent Engineering in Mould DesignConcurrent Engineering (CE) is a systematic approach to integrated product development process. It represents team values of co-operation, trust and sharing in such a manner that decision making is by consensus, involving all per spectives in parallel, from the very beginning of the productlife-cycle (Evans, 1998). Essentially, CE provides a collaborative, co-operative, collective and simultaneous engineering working environment. A concurrent engineering approach is based on five key elements:1. process2. multidisciplinary team3. integrated design model4. facility5. software infrastructureFigure 3 Methodologies in plastic injection mould design, a) Serial engineering b) Concurrent engineeringIn the plastics and mould industry, CE is very important due to the high cost tooling and long lead times. Typically, CE is utilized by manufacturing prototype tooling early in the design phase to analyze and adjust the design. Production tooling is manufactured as the final step. The manufacturing process and involving moulds must be designed after passing through the appearance evaluation and the structure optimization of the product design. CE requires an engineer to consider the manufacturing process of the designed product in the development phase.A good design of the product is unable to go to the market if its manufacturing process is impossible. Integration of process simulation and rapid prototyping and manufacturing can reduce the risk associated with moving from CAD to CAM and further enhance the validity of the product development.For years, designers have been restricted in what they can produce as they generally have todesign for manufacture (DFM) – that is, adjust their design intent to enable the component (or assembly) to be manufactured using a particular process or processes. In addition, if a mould is used to produce an item, there are therefore automatically inherent restrictions to the design imposed at the very beginning. Taking injection moulding as an example, in order to process a component successfully, at a minimum, the following design elements need to be taken into account:1. . geometry;. draft angles,. Non re-entrants shapes,. near constant wall thickness,. complexity,. split line location, and. surface finish,2. material choice;3. rationalisation of components (reducing assemblies);4. cost.In injection moulding, the manufacture of the mould to produce the injection-moulded components is usually the longest part of the product development process. When utilising rapid modelling, the CAD takes the longer time and therefore becomes the bottleneck.The process design and injection moulding of plastics involves rather complicated and time consuming activities including part design, mould design, injection moulding machine selection, production scheduling, tooling and cost estimation. Traditionally all these activities are done by part designers and mould making personnel in a sequential manner after completing injection moulded plastic part design. Obviously these sequential stages could lead to long product development time. However with the implementation of concurrent engineering process in the all parameters effecting product design, mould design, machine selection, production scheduling,tooling and processing cost are considered as early as possible in the design of the plastic part. When used effectively, CAE methods provide enormous cost and time savings for the part design and manufacturing. These tools allow engineers to virtually test how the part will be processed and how it performs during its normal operating life. The material supplier, designer, moulder and manufacturer should apply these tools concurrently early in the design stage of the plastic parts in order to exploit the cost benefit of CAE. CAE makes it possible to replace traditional, sequential decision-making procedures with a concurrent design process, in which all parties can interact and share information, Figure 3. For plastic injection moulding, CAE and related design data provide an integrated environment that facilitates concurrent engineering for the design and manufacture of the part and mould, as well as material selection and simulation of optimal process control parameters.Qualitative expense comparison associated with the part design changes is shown in Figure 4 , showing the fact that when design changes are done at an early stages on the computer screen, the cost associated with is an order of 10.000 times lower than that if the part is in production. These modifications in plastic parts could arise fr om mould modifications, such as gate location, thickness changes, production delays, quality costs, machine setup times, or design change in plastic parts.Figure 4 Cost of design changes during part product development cycle (Rios et.al, 2001)At the early design stage, part designers and moulders have to finalise part design based on their experiences with similar parts. However as the parts become more complex, it gets rather difficult to predict processing and part performance without the use of CAE tools. Thus for even relatively complex parts, the use of CAE tools to prevent the late and expensive design changesand problems that can arise during and after injection. For the successful implementation of concurrent engineering, there must be buy-in from everyone involved.5.Case StudyFigure 5 shows the initial CAD design of plastics part used for the sprinkler irrigation hydrant leg. One of the essential features of the part is that the part has to remain flat after injection; any warping during the injection causes operating problems.Another important feature the plastic part has to have is a high bending stiffness. A number of feeders in different orientation were added to the part as shown in Figure 5b. These feeders should be designed in a way that it has to contribute the weight of the part as minimum aspossible.Before the design of the mould, the flow analysis of the plastic part was carried out with Moldflow software to enable the selection of the best gate location Figure 6a. The figure indicates that the best point for the gate location is the middle feeder at the centre of the part. As the distortion and warpage of the part after injection was vital from the functionality point of view and it has to be kept at a minimum level, the same software was also utilised to yiled the warpage analysis. Figure 5 b shows the results implying the fact that the warpage well after injection remains within the predefined dimensional tolerances.6. ConclusionsIn the plastic injection moulding, the CAD model of the plastic part obtained from commercial 3D programs could be used for the part performance and injection process analyses. With the aid ofCEA technology and the use of concurrent engineering methodology, not only the injection mould can be designed and manufactured in a very short of period of time with a minimised cost but also all potential problems which may arise from part design, mould design and processing parameters could be eliminated at the very beginning of the mould design. These two tools help part designers and mould makers to develop a good product with a better delivery and faster tooling with less time and money.References1. Smith P, Reinertsen D, The time-to-market race, In: Developing Products in Half the Time. New York, Van Nostrand Reinhold, pp. 3–13, 19912.Thompson J, The total product development organization. Proceedings of the SecondAsia–Pacific Rapid Product Development Conference, Brisbane, 19963.Neel R, Don’t stop after the prototype, Seventh International Conference on Rapid Prototyping, San Francisco, 19974.Jacobs PF, “Chapter 3: Rapid Product Development” in Rapid Tooling: Technologies and Industrial Applications , Ed. Peter D. Hilton; Paul F. Jacobs, Marcel Decker, 20005.Lee R-S, Chen, Y-M, and Lee, C-Z, “Development of a concurrent mould design system: a knowledge based approach”, Computer Integrated Manufacturing Systems, 10(4), 287-307, 19976.Evans B., “Simultaneous Engineering”, Mechanical Engi neering , V ol.110, No.2, pp.38-39, 19987.Rios A, Gramann, PJ and Davis B, “Computer Aided Engineering in Compression Molding”, Composites Fabricators Association Annual Conference , Tampa Bay, 2001【译文一】塑料注塑模具并行设计塑料制品制造业近年迅速成长。
文献翻译-注塑模具
附页1:英文及中文翻译英文1.Example 24,Injection Mold for an Angle FitingIf ejectors are located behind movable side sores or slides ,the ejector plate return safety checks whether the ejectors have been returned to the molding position.If this is not the case,the molding cycle is interrupted.This safety requires a switch on the mold that is actuated when the ejector plate is in the retracted position. The ejector plate return safety thus functions only if the molding cycle utilizes platen preposition, i.e..,after the molded parts have been ejected, the clamping unit closes to the point at which the ejector plate is returned to the molding position by spring force. Only then does the control system issue the “close mold”command. In molds requiring a long ejector stroke, spring return of the ejector plate is often not sure enough. For such cases, there is an ejector return mechanism that fulfills this function.Attachment of the ejector plate return safety is shown in Figs.1 to 7.This single-cavity mold is used to produce an angle fitting.Two long side cores meet at an angle of 90°.The somewhat shorter side core is pulled by a cam pin,while the longer core is pulled by a slide.The difficulty is that blade ejectors are located under the two cores and must be returned to the molding position after having Ejected the finished part before the two cores are set as the mold closes and possibly damage the blade ejectors .Possible consequences include not only broken blade ejectors but also a damaged cavity. Either of these could result in a lengthy interruption of production. For this reason, a helical spring that permits operation with platen prepostion is placed on the ejector rod. This spring then returns the ejector plate .To ensure proper operation, a microswitch is mounted to the clamping plate,while a pin that actuates the switch is mounted in the ejector plate.After connecting the cable with the switch housing of the movable clamping plate,the ejector plate return safety is complete.Example 25,Mold for Bushings with Concealed Gating2.Example 25, Mold for Bushings with Concealed GatingAflanged bushing is to be injection molded in such a way that any remnants ofthe gate are concealed or as inconspicuous as possible.The bushing would normally require a two-plate mold with a single parting line,The molded part would then be released and ejected along its axis, which coincides with the opening direction of the mold. The gate would be located on the outer surface of the flange since it is in contact with the mold parting line.In order to satisfy the requirement for an “invisible”gate,the cavities (two rows of four) are placed between slides carrying the cores even though there are no undercuts.From a central sprue the melt flows through conical runners in the cores to pinpoint gates located on the inner surface of the bushings. As the slides move during opening of the mold the gates are cleanly sheared off flush with the adjacent part surface. The flexibility of the plastic selected is sufficient to permit release of the end of the runner from the angled runner channel.The parts are now free and can drop out of the mold.3. Example 26,Injection Mold for the Valave Housing of a Water-Mixing Tap Made from PolyacetalA valve housing had to be designed and produced for a water-mixing tap.The problem when designing the tool resulted from the undercuts in four directions.Originally occurring considerable differences in wall thicknesses have been eliminated during optimization. Demands for high precision of the cylindrical vave seat in parti-cular wer negatively influenced by various recesses in the wall and adjoining partitions,which favored sink marks and ovalness.Polyaceta (POM) had been chosen as molding materia.The complete molded part had to have homogeneous walls,and be free from flow lines if at all possible, as it would be subjected to ever-changing contact with hot and cold water during an estimated long life span.Inadequately fused weld lines would be capable of developoing into weak spots and wer therefore to be avoided at all cost.Provision has been made for an electrically heated sprue bushing in order to avoid a long sprue,provide better movement energies for the melt and maintain its temperature until it enters the cavity.The resultant very short runner leads to the gate on the edge of the pipelike housing, to be hidden by a part that is subsequently fitted to cover it.The gating,the predetermined mold temperature,the wall thickness at the critical positions and the resultant shrinkage have been employed as the basis for dimensioning the part-forming components.Two cores each cross in the pipe-shaped housing,i.e.one core each penetrates another core.This obviously presents a danger spot should the minutest deviation occur from the specified time and movement-based coordination as well as from the accuracy in the mold.The hollow cores are kept in position by mechanical delay during the first phase of mold opening,while the crossing cores are each withdrawn by an angle pin . Mechanical actuation has been preferred over a hydraulic or pneumatic one in this case in order to exclude the danger of a sequencing error (the so-called human factor) during set-up and operation.The cores consist of a beryllium-copper alloy. They are cooled by heat conducting pins.4.Example 29,Injection Mold for the Housing of a Polypropylene Vegetable DicerMolded PartThe housing accommodates a cutting disc that is driven by a hand crank . The shaft of the crank drive is located in a bore in the housing. The underneath of the housing has a recess for accommodating a suction cap to attach the device to a table. The top of the housing has a filling shaft which supplies the cutting disc with the vegetables to be diced. A feed hopper will be attached to this filling shaft.The molded part weighs 386 g.MoldThe mold was designed so that the dicing chamber lies in the mold-opening direction.The housing base,the filling shaft and two other apertures are ejected with the aid of splits ,a core puller and slides.The slide,moved by the angle pin,forms the inside contour of the housing base .In the closed position,the split shoulder lies against punch and so forms the bore for attaching the suction cap to the housing base .The cylindrical slide lies in the mold parting line and each half is enclosed by the mold plates and.Guide strips lead the slide on the mold plate. The slide supports itself against the effect of the cavity pressure via the adjusting plate and the wedge. Bending of the wedge is prevented by the adjusting plate and the mold plate. The vegetable filling shaft and the passage to the dicing chamber are formed by the mobile core. Its movement is provided by the angle pin.Figure 7 shows the core guide in the guide strip.The inserted core is locked via the wedge and adjusting plate .The guide strip forms a rectangular opening in theside wall of the housing which lies half over and half under the mold parting line. It is moved by two angle pins and is locked in the closed state by two bolts. A guide strip which is bolted and doweled to the mold plate is guided in a T-solt.Finally, a slit has to be formed in the housing wall that penetrates a reinforcement there. Rectangular aperture and reinforcement are formed by the slide which is actuated by the angle pin and locked by the wedge.Two bars serve to guide the slide on the mold plate. Since the angle pins traverse out from the slide ,the core and the guide bars on mold opening, each is provided with ball catches that keep these guide elements in the “open” position. Bars and rolls support the plate on the clamp plate.Runner System/GatingThe sprue bushing lies on the axis of the housing bore, which accommodates the blade drive shaft.The end of the sprue bushing forms the face of an eye inside the dicing chamber that is a part of the crankshaft mount. A core pin protrudes into the bore of the sprue bushing and divides the sprue into three pinpoint gates.Mold Temperature ControlThe coolant is guided in bores and cooling channels in the mold plates, inserts and punches.The splits and offer sufficient space for accommodating cooling channels..Part Release/EjectionOn mold opening,the angle pins on the fixed mold side push the splits ,cores and slides on the moving side so far outward that they release the undercuts of the housing. The molded part remanis on the moving mold side.Ejector pins and ejector sleeve push the molded part out of the ejector-side mold cavities and off core pin. Since the ejector pins are contour-forming,they must be secured against twisting . On mold closing, the ejector system is brought into the injection molding position by ejector-plate return pins and buffer pins,and so too are the splits ,cores and slides by their respective angle pints.译文1.注塑模具角度为拟合如果喷射器是可移动的侧后面疮或幻灯片位于顶针板返回安全的喷射器是否已返回成型,这是不是这样,成型周期检查中断。
注塑模具之模具设计与制造外文文献翻译、中英文翻译
外文翻译:Injection moulding for Mold Design and ManufactureThe mold is the manufacturing industry important craft foundation, in our country, the mold manufacture belongs to the special purpose equipment manufacturing industry. China although very already starts to make the mold and the use mold, but long-term has not formed the industry. Straight stabs 0 centuries 80's later periods, the Chinese mold industry only then drives into the development speedway. Recent years, not only the state-owned mold enterprise had the very big development, the three investments enterprise, the villages and towns (individual) the mold enterprise's development also quite rapidly.Although the Chinese mold industrial development rapid, but compares with the demand, obviously falls short of demand, its main gap concentrates precisely to, large-scale, is complex, the long life mold domain. As a result of in aspect and so on mold precision, life, manufacture cycle and productivity, China and the international average horizontal and the developed country still had a bigger disparity, therefore, needed massively to import the mold every year .The Chinese mold industry except must continue to sharpen the productivity; from now on will have emphatically to the profession internal structure adjustment and the state-of-art enhancement. The structure adjustment aspect, mainly is the enterprise structure to the specialized adjustment, the product structure to center the upscale mold development, to the import and export structure improvement, center the upscale automobile cover mold forming analysis and the structure improvement, the multi-purpose compound mold and the compound processing and the laser technology in the mold design manufacture application, the high-speed cutting, the super finishing and polished the technology, the information direction develops .The recent years, the mold profession structure adjustment and the organizational reform step enlarges, mainly displayed in, large-scale, precise, was complex, the long life, center the upscale mold and the mold standard letter development speed is higher than the common mold product; The plastic mold and the compression casting moldproportion increases; Specialized mold factory quantity and its productivity increase; "The three investments" and the private enterprise develops rapidly; The joint stock system transformation step speeds up and so on. Distributes from the area looked, take Zhujiang Delta and Yangtze River delta as central southeast coastal area development quickly to mid-west area, south development quickly to north. At present develops quickest, the mold produces the most centralized province is Guangdong and Zhejiang, places such as Jiangsu, Shanghai, Anhui and Shandong also has a bigger development in recent years.Although our country mold total quantity had at present achieved the suitable scale, the mold level also has the very big enhancement, after but design manufacture horizontal overall rise and fall industry developed country and so on Yu De, America, date, France, Italy many. The current existence question and the disparity mainly display in following several aspects:(1) The total quantity falls short of demandDomestic mold assembling one rate only, about 70%. Low-grade mold, center upscale mold assembling oneself rate only has 50% about.(2) The enterprise organizational structure, the product structure, the technical structure and the import and export structure does not gatherIn our country mold production factory to be most is from the labor mold workshop which produces assembles oneself (branch factory), from produces assembles oneself the proportion to reach as high as about 60%, but the overseas mold ultra 70% is the commodity mold. The specialized mold factory mostly is "large and complete", "small and entire" organization form, but overseas mostly is "small but", "is specially small and fine". Domestic large-scale, precise, complex, the long life mold accounts for the total quantity proportion to be insufficient 30%, but overseas in 50% above 2004 years, ratio of the mold import and export is 3.7:1, the import and export balances the after net import volume to amount to 1.32 billion US dollars, is world mold net import quantity biggest country .(3) The mold product level greatly is lower than the international standardThe production cycle actually is higher than the international water broadproduct level low mainly to display in the mold precision, cavity aspect and so on surface roughness, life and structure.(4) Develops the ability badly, economic efficiency unsatisfactory our country mold enterprise technical personnel proportion lowThe level is lower, also does not take the product development, and frequently is in the passive position in the market. Our country each mold staff average year creation output value approximately, ten thousand US dollars, overseas mold industry developed country mostly 15 to10, 000 US dollars, some reach as high as 25 to10, 000 US dollars, relative is our country quite part of molds enterprises also continues to use the workshop type management with it, truly realizes the enterprise which the modernized enterprise manages fewTo create the above disparity the reason to be very many, the mold long-term has not obtained the value besides the history in as the product which should have, as well as the most state-owned enterprises mechanism cannot adapt the market economy, but also has the following several reasons: .The mold material performance, the quality and the variety question often can affect the mold quality, the life and the cost, the domestically produced molding tool steel and overseas imports the steel products to compare has a bigger disparity. Plastic,plate, equipment energy balance, also direct influence mold level enhancement.RSP ToolingRapid Solidification Process (RSP) Tooling, is a spray forming technology tailored for producing molds and dies [2-4]. The approach combines rapid solidification processing and netshape materials processing in a single step. The general concept involves converting a mold design described by a CAD file to a tooling master using a suitable rapid prototyping (RP) technology such as stereolithography. A pattern transfer is made to a castable ceramic, typically alumina or fused silica. This is followed by spray forming a thick deposit of tool steel (or other alloy) on the pattern to capture the desired shape, surface texture and detail. The resultant metal block is cooled to room temperature and separated from the pattern. Typically, the deposit’s exterior walls are machined square, allowing it to be used as an insert in a holding block such as a MUD frame [5]. The overall turnaround time for tooling is about three days, stating with a master. Molds and dies produced in this way have been used for prototype and production runs in plastic injection molding and die casting.An important benefit of RSP Tooling is that it allows molds and dies to be made early in the design cycle for a component. True prototype parts can be manufactured to assess form, fit, and function using the same process planned for production. If the part is qualified, the tooling can be run in production as conventional tooling would. Use of a digital database and RP technology allows design modifications to be easily made.Experimental ProcedureAn alumina-base ceramic (Cotronics 780 [6]) was slurry cast using a silicone rubber master die, or freeze cast using a stereolithography master. After setting up, ceramic patterns were demolded, fired in a kiln, and cooled to room temperature. H13 tool steel was induction melted under a nitrogen atmosphere, superheated about100︒C, and pressure-fed into a bench-scale converging/diverging spray nozzle, designed and constructed in-house. An inert gas atmosphere within the spray apparatus minimized in-flight oxidation of the atomized droplets as they deposited onto the tool pattern at a rate of about 200 kg/h. Gas-to-metal mass flow ratio was approximately 0.5.For tensile property and hardness evaluation, the spray-formed material was sectioned using a wire EDM and surface ground to remove a 0.05 mm thickheat-affected zone. Samples were heat treated in a furnace that was purged with nitrogen. Each sample was coated with BN and placed in a sealed metal foil packet as a precautionary measure to prevent decarburization.Artificially aged samples were soaked for 1 hour at temperatures ranging from 400 to 700︒C, and air cooled. Conventionally heat treated H13 was austenitized at 1010︒C for 30 min., air quenched, and double tempered (2 hr plus 2 hr) at 538︒C.Microhardness was measured at room temperature using a Shimadzu Type M Vickers Hardness Tester by averaging ten microindentation readings. Microstructure of the etched (3% nital) tool steel was evaluated optically using an Olympus Model PME-3 metallograph and an Amray Model 1830 scanning electron microscope. Phase composition was analyzed via energy-dispersive spectroscopy (EDS). The size distribution of overspray powder was analyzed using a Microtrac Full Range Particle Analyzer after powder samples were sieved at 200 μm to remove coarse flakes. Sample density was evaluated by water displacement using Archimedes’ principle and a Mettler balance (Model AE100).A quasi 1-D computer code developed at INEEL was used to evaluate multiphase flow behavior inside the nozzle and free jet regions. The code's basic numerical technique solves the steadystate gas flow field through an adaptive grid, conservative variables approach and treats the droplet phase in a Lagrangian manner with full aerodynamic and energetic coupling between the droplets and transport gas. The liquid metal injection system is coupled to the throat gas dynamics, and effects of heat transfer and wall friction are included. The code also includes a nonequilibriumsolidification model that permits droplet undercooling and recalescence. The code was used to map out the temperature and velocity profile of the gas and atomized droplets within the nozzle and free jet regions.Results and DiscussionSpray forming is a robust rapid tooling technology that allows tool steel molds and dies to be produced in a straightforward manner. Each was spray formed using a ceramic pattern generated from a RP master.Particle and Gas BehaviorParticle mass frequency and cumulative mass distribution plots for H13 tool steel sprays are given in Figure 1. The mass median diameter was determined to be 56 μm by interpolation of size corresponding to 50% cumulative mass. The area mean diameter and volume mean diameter were calculated to be 53 μm and 139 μm, respectively. Geometric standard deviation, d=(d84/d16)½ , is 1.8, where d84 and d16 are particle diameters corresponding to 84% and 16% cumulative mass in Figure 1.Figure1. Cumulative mass and mass frequency plots of particles in H13 tool stepsprays.Figure2 gives computational results for the multiphase velocity flow field (Figure 2a), and H13 tool steel solid fraction (Figure2b), inside the nozzle and free jetregions. Gas velocity increases until reaching the location of the shock front, at which point it precipitously decreases, eventually decaying exponentially outside the nozzle. Small droplets are easily perturbed by the velocity field, accelerating inside the nozzle and decelerating outside. After reaching their terminal velocity, larger droplets (〜150 μm) are less perturbed by the flow field due to their greater momentum.It is well known that high particle cooling rates in the spray jet (103-106 K/s) and bulk deposit (1-100 K/min) are present during spray forming [7]. Most of the particles in the spray have undergone recalescence, resulting in a solid fraction of about 0.75. Calculated solid fraction profiles of small (〜30 μm) and large (〜150 μm) droplets with distance from the nozzle inlet, are shown in Figure 2b.Spray-Formed DepositsThis high heat extraction rate reduces erosion effects at the surface of the tool pattern. This allows relatively soft, castable ceramic pattern materials to be used that would not be satisfactory candidates for conventional metal casting processes. With suitable processing conditions, fine surface detail can be successfully transferred from the pattern to spray-formed mold. Surface roughness at the molding surface is pattern dependent. Slurry-cast commercial ceramics yield a surface roughness of about 1 μm Ra, suitable for many molding applications. Deposition of tool steel onto glass plates has yielded a specular surface finish of about 0.076 μm Ra. At the current state of development, dimensional repeatability of spray-formed molds, starting with a common master, is about ±0.2%.Figure 2. Calculated particle and gas behavior in nozzle and free jet regions.(a) Velocity profile.(b) Solid fraction.ChemistryThe chemistry of H13 tool steel is designed to allow the material to withstand the temperature, pressure, abrasion, and thermal cycling associated with demanding applications such as die casting. It is the most popular die casting alloy worldwide and second most popular tool steel for plastic injection molding. The steel has low carbon content (0.4 wt.%) to promote toughness, medium chromium content (5 wt.%) to provide good resistance to high temperature softening, 1 wt% Si to improve high temperature oxidation resistance, and small molybdenum and vanadium additions (about 1%) that form stable carbides to increase resistance to erosive wear[8]. Composition analysis was performed on H13 tool steel before and after spray forming.Results, summarized in Table 1, indicate no significant variation in alloy additions.MicrostructureThe size, shape, type, and distribution of carbides found in H13 tool steel is dictated by the processing method and heat treatment. Normally the commercial steel is machined in the mill annealed condition and heat treated(austenitized/quenched/tempered) prior to use. It is typically austenitized at about 1010︒C, quenched in air or oil, and carefully tempered two or three times at 540 to 650︒C to obtain the required combination of hardness, thermal fatigue resistance, and toughness.Commercial, forged, ferritic tool steels cannot be precipitation hardened becauseafter electroslag remelting at the steel mill, ingots are cast that cool slowly and formcoarse carbides. In contrast, rapid solidification of H13 tool steel causes alloying additions to remain largely in solution and to be more uniformly distributed in the matrix [9-11]. Properties can be tailored by artificial aging or conventional heat treatment.A benefit of artificial aging is that it bypasses the specific volume changes that occur during conventional heat treatment that can lead to tool distortion. These specific volume changes occur as the matrix phase transforms from ferrite to austenite to tempered martensite and must be accounted for in the original mold design. However, they cannot always be reliably predicted. Thin sections in the insert, which may be desirable from a design and production standpoint, are oftentimes not included as the material has a tendency to slump during austenitization or distort during quenching. Tool distortion is not observed during artificial aging ofspray-formed tool steels because there is no phase transformation.注塑模具之模具设计与制造模具是制造业的重要工艺基础,在我国,模具制造属于专用设备制造业。
注塑模具外文 文献资料2
Journal of Materials Processing Technology187–188 (2007) 690–693Adaptive system for electrically driven thermoregulationof moulds for injection mouldingB.Nardin a,∗,B.ˇZagar a,∗,A.Glojek a,D.Kriˇz aj ba TECOS,Tool and Die Development Centre of Slovenia,Kidriˇc eva Cesta25,3000Celje,Sloveniab Faculty of Electrical Engineering,Ljubljana,SloveniaAbstractOne of the basic problems in the development and production process of moulds for injection moulding is the control of temperature con-ditions in the mould.Precise study of thermodynamic processes in moulds showed,that heat exchange can be manipulated by thermoelectrical means.Such system upgrades conventional cooling systems within the mould or can be a stand alone application for heat manipulation within it.In the paper,the authors will present results of the research project,which was carried out in three phases and its results are patented in A686\2006 patent.The testing stage,the prototype stage and the industrialization phase will be presented.The main results of the project were total and rapid on-line thermoregulation of the mould over the cycle time and overall influence on quality of plastic product with emphasis on deformation control.Presented application can present a milestone in thefield of mould temperature and product quality control during the injection moulding process.© 2006 Elsevier B.V. All rights reserved.Keywords:Injection moulding;Mould cooling;Thermoelectric modules;FEM simulations1.Introduction,definition of problemDevelopment of technology of cooling moulds via thermo-electrical(TEM)means derives out of the industrial praxis and problems,i.e.at design,tool making and exploitation of tools. Current cooling technologies have technological limitations. Their limitations can be located and predicted in advance with finite element analyses(FEA)simulation packages but not com-pletely avoided.Results of a diverse state of the art analyses revealed that all existing cooling systems do not provide con-trollable heat transfer capabilities adequate tofit into demand-ing technological windows of current polymer processing technologies.Polymer processing is nowadays limited(in term of short-ening the production cycle time and within that reducing costs) only with heat capacity manipulation capabilities.Other produc-tion optimization capabilities are already driven to mechanical and polymer processing limitations[3].∗Corresponding authors.Tel.:+3863490920;fax:+38634264612.E-mail address:Blaz.Nardin@tecos.si(B.Nardin).1.1.Thermal processes in injection moulding plastic processingPlastic processing is based on heat transfer between plastic material and mould cavity.Within calculation of heat transfer one should consider two major facts:first is all used energy which is based onfirst law of thermodynamics—law of energy conservation[1],second is velocity of heat transfer.Basic task at heat transfer analyses is temperature calculation over time and its distribution inside studied system.That last depends on velocity of heat transfer between the system and surroundings and velocity of heat transfer inside the system.Heat transfer can be based as heat conduction,convection and radiation[1].1.2.Cooling timeComplete injection moulding process cycle comprises of mould closing phase,injection of melt into cavity,packing pres-sure phase for compensating shrinkage effect,cooling phase, mould opening phase and part ejection phase.In most cases,the longest time of all phases described above is cooling time.Cooling time in injection moulding process is defined as time needed to cool down the plastic part down to ejection temperature[1].0924-0136/$–see front matter© 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.11.052B.Nardin et al./Journal of Materials Processing Technology 187–188 (2007) 690–693691Fig.1.Mould temperature variation across one cycle[2].The main aim of a cooling process is to lower additional cooling time which is theoretically needless;in praxis,it extends from45up to67%of the whole cycle time[1,4].From literature and experiments[1,4],it can be seen,that the mould temperature has enormous influence on the ejection time and therefore the cooling time(costs).Injection moulding process is a cyclic process where mould temperature varies as shown in Fig.1where temperature varies from average value through whole cycle time.2.Cooling technology for plastic injection mouldsAs it was already described,there are already several differ-ent technologies,enabling the users to cool the moulds[5].The most conventional is the method with the drilling technology, i.e.producing holes in the mould.Through these holes(cooling lines),the cooling media isflowing,removing the generated and accumulated heat from the mould[1,2].It is also very convenient to build in different materials,with different thermal conductiv-ity with the aim to enhance control over temperature conditions in the mould.Such approaches are so called passive approaches towards the mould temperature control.The challenging task is to make an active system,which can alter the thermal conditions,regarding to the desired aspects, like product quality or cycles time.One of such approaches is integrating thermal electrical modules(TEM),which can alter the thermal conditions in the mould,regarding the desired prop-erties.With such approach,the one can control the heat transfer with the time and space variable,what means,that the temper-ature can be regulated throughout the injection moulding cycle, independent of the position in the mould.The heat control is done by the control unit,where the input variables are received from the manual input or the input from the injection moulding simulation.With the output values,the control unit monitors the TEM module behaviour.2.1.Thermoelectric modules(TEM)For the needs of the thermal manipulation,the TEM module was integrated into mould.Interaction between the heat and elec-trical variables for heat exchange is based on the Peltier effect. The phenomenon of Peltier effect is well known,but it wasuntilFig.2.TEM block diagram.now never used in the injection moulding applications.TEM module(see Fig.2)is a device composed of properly arranged pairs of P and N type semiconductors that are positioned between two ceramic plates forming the hot and the cold thermoelectric cooler sites.Power of a heat transfer can be easily controlled through the magnitude and the polarity of the supplied electric current.2.2.Application for mould coolingThe main idea of the application is inserting TEM module into walls of the mould cavity serving as a primary heat transfer unit.Such basic assembly can be seen in Fig.3.Secondary heat transfer is realized via conventionalfluid cooling system that allows heatflows in and out from mould cavity thermodynamic system.Device presented in Fig.3comprises of thermoelectric modules(A)that enable primarily heat transfer from or to tem-perature controllable surface of mould cavity(B).Secondary heat transfer is enabled via cooling channels(C)that deliver constant temperature conditions inside the mould.Thermoelec-tric modules(A)operate as heat pump and as such manipulate with heat derived to or from the mould byfluid cooling sys-tem(C).System for secondary heat manipulation with cooling channels work as heat exchanger.To reduce heat capacity of controllable area thermal insulation(D)is installed between the mould cavity(F)and the mould structure plates(E).Fig.3.Structure of TEM cooling assembly.692 B.Nardin et al./Journal of Materials ProcessingTechnology 187–188 (2007) 690–693Fig.4.Structure for temperature detection and regulation.The whole application consists of TEM modules,a temper-ature sensor and an electronic unit that controls the complete system.The system is described in Fig.4and comprises of an input unit(input interface)and a supply unit(unit for electronic and power electronic supply—H bridge unit).The input and supply units with the temperature sensor loop information are attached to a control unit that acts as an exe-cution unit trying to impose predefined temperate/time/position ing the Peltier effect,the unit can be used for heating or cooling purposes.The secondary heat removal is realized viafluid cooling media seen as heat exchanger in Fig.4.That unit is based on current cooling technologies and serves as a sink or a source of a heat.This enables complete control of processes in terms of temperature,time and position through the whole cycle. Furthermore,it allows various temperature/time/position pro-files within the cycle also for starting and ending procedures. Described technology can be used for various industrial and research purposes where precise temperature/time/position con-trol is required.The presented systems in Figs.3and4were analysed from the theoretical,as well as the practical point of view.The theoretical aspect was analysed by the FEM simulations,while the practical one by the development and the implementation of the prototype into real application testing.3.FEM analysis of mould coolingCurrent development of designing moulds for injection moulding comprises of several phases[3].Among them is also design and optimization of a cooling system.This is nowa-days performed by simulations using customized FEM packages (Moldflow[4])that can predict cooling system capabilities and especially its influence on plastic.With such simulations,mould designers gather information on product rheology and deforma-tion due to shrinkage as ell as production time cycle information.This thermal information is usually accurate but can still be unreliable in cases of insufficient rheological material informa-tion.For the high quality input for the thermal regulation of TEM,it is needed to get a picture about the temperature distri-bution during the cycle time and throughout the mould surface and throughout the mould thickness.Therefore,different process simulations areneeded.Fig.5.Cross-section of a prototype in FEM environment.3.1.Physical model,FEM analysisImplementation of FEM analyses into development project was done due to authors’long experiences with such packages [4]and possibility to perform different test in the virtual envi-ronment.Whole prototype cooling system was designed in FEM environment(see Fig.5)through which temperature distribution in each part of prototype cooling system and contacts between them were explored.For simulating physical properties inside a developed prototype,a simulation model was constructed using COMSOL Multiphysics software.Result was a FEM model identical to real prototype(see Fig.7)through which it was possible to compare and evaluate results.FEM model was explored in term of heat transfer physics taking into account two heat sources:a water exchanger with fluid physics and a thermoelectric module with heat transfer physics(only conduction and convection was analysed,radiation was ignored due to low relative temperature and therefore low impact on temperature).Boundary conditions for FEM analyses were set with the goal to achieve identical working conditions as in real test-ing.Surrounding air and the water exchanger were set at stable temperature of20◦C.Fig.6.Temperature distribution according to FEM analysis.B.Nardin et al./Journal of Materials Processing Technology 187–188 (2007) 690–693693Fig.7.Prototype in real environment.Results of the FEM analysis can be seen in Fig.6,i.e.temper-ature distribution through the simulation area shown in Fig.5. Fig.6represents steady state analysis which was very accurate in comparison to prototype tests.In order to simulate the time response also the transient simulation was performed,showing very positive results for future work.It was possible to achieve a temperature difference of200◦C in a short period of time(5s), what could cause several problems in the TEM structure.Those problems were solved by several solutions,such as adequate mounting,choosing appropriate TEM material and applying intelligent electronic regulation.boratory testingAs it was already described,the prototype was produced and tested(see Fig.7).The results are showing,that the set assump-tions were confirmed.With the TEM module it is possible to control the temperature distribution on different parts of the mould throughout the cycle time.With the laboratory tests,it was proven,that the heat manipulation can be practically regu-lated with TEM modules.The test were made in the laboratory, simulating the real industrial environment,with the injection moulding machine Krauss Maffei KM60C,temperature sen-sors,infrared cameras and the prototype TEM modules.The temperature response in1.8s varied form+5up to80◦C,what represents a wide area for the heat control within the injection moulding cycle.4.ConclusionsUse of thermoelectric module with its straightforward con-nection between the input and output relations represents a milestone in cooling applications.Its introduction into moulds for injection moulding with its problematic cooling construction and problematic processing of precise and high quality plastic parts represents high expectations.The authors were assuming that the use of the Peltier effect can be used for the temperature control in moulds for injection moulding.With the approach based on the simulation work and the real production of laboratory equipment proved,the assump-tions were confirmed.Simulation results showed a wide area of possible application of TEM module in the injection moulding process.With mentioned functionality of a temperature profile across cycle time,injection moulding process can be fully controlled. Industrial problems,such as uniform cooling of problematic A class surfaces and its consequence of plastic part appear-ance can be solved.Problems offilling thin long walls can be solved with overheating some surfaces at injection time.Further-more,with such application control over rheological properties of plastic materials can be gained.With the proper thermal regulation of TEM it was possible even to control the melt flow in the mould,during thefilling stage of the mould cav-ity.This is done with the appropriate temperature distribution of the mould(higher temperature on the thin walled parts of the product).With the application of TEM module,it is possible to signif-icantly reduce the cycle time in the injection moulding process. The limits of possible time reduction lies in the frame of10–25% of additional cooling time,describe in Section1.2.With the application of TEM module it is possible to actively control the warping of the product and to regulate the amount of product warpage in the way to achieve required product tol-erances.The presented TEM module cooling application for injection moulding process is a matter of priority note for the patent,held and owned by TECOS.References[1]I.ˇCati´c,Izmjena topline u kalupima za injekcijsko preˇs anje plastomera,Druˇs tvo plastiˇc ara i gumaraca,Zagreb,1985.[2]I.ˇCati´c,F.Johannaber,Injekcijsko preˇs anje polimera i ostalih materiala,Druˇs tvo za plastiku i gumu,Biblioteka polimerstvo,Zagreb,2004.[3]B.Nardin,K.Kuzman,Z.Kampuˇs,Injection moulding simulation resultsas an input to the injection moulding process,in:AFDM2002:The Sec-ond International Conference on Advanced Forming and Die Manufacturing Technology,Pusan,Korea,2002.[4]TECOS,Slovenian Tool and Die Development Centre,Moldflow SimulationProjects1996–2006.[5]S.C.Chen,et al.,Rapid mold surface heating/cooling using electromag-netic induction technology:ANTEC2004,Conference CD-ROM,Chicago, Illinois,16–20May,2004.。
模具 塑料注射成型 外文翻译 外文文献 英文文献
模具塑料注射成型外文翻译外文文献英文文献XXXThere are many different processing methods used to convert plastic pellets。
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模具外文翻译外文文献英文文献注塑模
模具外文翻译外文文献英文文献注塑模The Injection Molding1、The injection moldingInjection molding is principally used for the production of the thermoplastic parts,although some progress has been made in developing a method for injection molding some thermosetting materials.The problem of injection a method plastic into a mold cavity from a reservoir of melted material has been extremely difficult to solve for thermosetting plastic which cure and harden under such conditions within a few minutes.The principle of injection molding is quite similar to that of die-casting.The process consists of feeding a plastic compound in powered or granular form from a hopper through metering and melting stages and then injecting it into a mold.After a brief cooling period,the mold is opened and the solidified part ejected.Injection-molding machine operation.The advantage of injection molding are:(ⅰ)a high molding speed adapter for mass production is possible;(ⅱ)there is a wide choice of thermoplastic materials providing a variety of useful properties;(ⅲ)it is possible to mold threads,undercuts,side holes,and large thin section.2、The injection-molding machineSeveral methods are used to force or inject the melted plastic into the mold.The most commonly used system in the larger machines is the in-line reciprocating screw,as shown in Figure 2-1.The screw acts as a combination injection and plasticizing unit.As the plastic is fed to the rotating screw,it passes through three zones as shown:feed,compression,and metering.After the feed zone,the screw-flight depth is gradually reduced,force theplastic to compress.The work is converted to heat by conduction from the barrel surface.As the chamber in front of the screw becomes filled,it forces the screw back,tripping a limit switch that activates a hydraulic cylinder that forces the screw forward and injects the fluid plastic into the closed mold.An antiflowback valve presents plastic under pressure from escaping back into the screw flight.The clamping force that a machine is capable of exerting is part of the size designation and is measured in tons.A rule-of-thumb can be used to determine the tonnage required for a particular job.It is based on two tons of clamp force per square inch of projected area.If the flow pattern is difficult and the parts are thin,this may have to go to three or four tons.Many reciprocating-screw machines are capable of handing thermosetting plastic materials.Previously these materials were handled by compression or transfer molding.Thermosetting materials cure or polymerize in the mold and are ejected hot in the range of 375°C~410°C.T hermosetting parts must be allowed to cool in the mold in order or remove them without distortion. Thus thermosetting cycles can be faster.Of course the mold must be heated rather than chilled,as with thermoplastics.3、Basic Underfeed MouldA simple mould of this type is shown in Figure3-1,and the description of the design and the opening sequence follows.The mould consists of three basic parts,namely:the moving half,the floating cavity plate and the feed plate respectively.The moving half consists of The moving mould plate assembly,support block,backing plate,ejector assembly and the pin ejection system.Thus the moving half in this design is identical with the moving half of basic moulds.The floating cavity plate,which may be of the integer or insert-bolster design,is located on substantial guide pillars(not shown)fitted in the feed plate.These guide pillars must be of sufficient length to support the floating cavity plate over its full movement and still project to perform the function of alignment between the cavity and core when the mould is being closed.Guide bushes are fitted into the moving mould plate and the floating cavity plate respectively.The maximum movement of the floating cavity plate is controlled by stop or similar device.The moving mould plate is suitably bored to provide a clearance for the stop bolt assembly.The stop bolts must be long enough to provide sufficient space between the feed plate and the floating cavity plate for easy removal of the feed system.The minimum space provide for should be 65mm just sufficient for an operator to remove the feed system by hand if necessary.The desire operating sequence is for the first daylight to occur between the floating cavity plate.This ensures the sprue is pulled from the sprue bush immediately the mouldis opened.T o achieve this sequence,springs may be incorporated between the feed plate and the floating cavity plate.The springs should be strong enough to give an initial impetus to the floating cavity plate to ensure it moves away with the moving half.It is normal practice to mount the springs on the guide pillars(Figure3-2)and accommodate them in suitable pocket in the cavity plate.The major part of the feed system(runner and sprue)is accommodated in the feed plate to facilitate automatic operation,the runner should be of a trapezoidal form so that once it is pulled from the feed plate is can easily beextracted.Note that if a round runner is used,half the runner is formed in the floating cavity plate,where it would remain,and be prevented from falling or being wiped clear when the mould is opened.Now that we have considered the mould assembly in the some detail,we look at the cycle of operation for this type of mould.The impressions are filled via the feed system(Figure3-1(a))and after a suitable dwell period,the machine platens commence to open.A force is immediately exerted by the compression springs,which cause the floating cavity plate to move away with the moving half as previously discussed.The sprue is pulled from the sprue bush by the sprue puller.After the floating cavity plate has moved a predetermined distance,it is arrested by the stop bolts.The moving half continues to move back and the moldings,having shrunk on to the cores,are withdrawn from the cavities.The pin gate breaks at its junction with the runner(Figure3-1(b)).The sprue puller,being attached to the moving half,is pulled through the floating cavity plate and thereby release the feed system which is then free to fall between the floating cavity plate and the feed plate.The moving half continues to move back until the ejector system is operated and the moldings are ejected (Figure3-1(c)).When the mould is closed,the respective plates are returned to their molding position and the cycle is repeated.4、Feed SystemIt is necessary to provide a flow-way in the injection mould to connect the nozzle(of the injection machine)to each impression.This flow-way is termed the feed system.Normally thefeed system comprises a sprue,runner and gate.These terms applyequally to the flow-way itself,and to the molded material which is remove from the flow-way itself in the process of extracted the molding.A typical feed system for a four-impression,two plate-type mould is shown in Figure4-1.It is seen that the material passes through the sprue,main runner,branch runner and gate before entering the impression.As the temperature of molten plastic is lowered which going through the sprue and runner,the viscosity will rise;however,the viscosity is lowered by shear heat generated when going through the gate to fill the cavity.It is desirable to keep the distance that the material has to travel down to a minimum to reduce pressure and heat losses.It is for this reason that careful consideration must be given to the impression layout gate’s design.4.1.SprueA sprue is a channel through which to transfer molten plastic injected from the nozzle of the injector into the mold.It is a part of sprue bush,which is a separate part from the mold.4.2.RunnerA runner is a channel that guides molten plastic into the cavity of a mold.4.3.GateA gate is an entrance through which molten plastic enters the cavity.The gate has the following function:restricts the flow and the direction of molten plastic;simplifies cutting of a runner and moldings to simplify finishing of parts;quickly cools and solidifies to avoid backflow after molten plastic has filled up in the cavity.4.4.Cold slug wellThe purpose of the cold slug well,shown opposite the sprue,is theoretically to receive the material that has chilled at the front of nozzle during the cooling and ejection phase.Perhaps of greater importance is the fact that it provides position means whereby the sprue bush for ejection purposes.The sprue,the runner and the gate will be discarded after a part is complete.However,the runner and the gate are important items that affect the quality or the cost of parts.5、EjectionA molding is formed in mould by injecting a plastic melt,under pressure,into animpression via a feed system.It must therefore be removed manually.Furthermore,all thermoplastic materials contract as they solidify,which means that the molding will shrink on to the core which forms it.This shrinkage makes the molding difficult to remove. Facilities are provided on the injection machine for automatic actuation of an ejector system,and this is situated behind the moving platen.Because of this,the mould’s ejector system will be most effectively operated if placed in the moving half of the mould,i.e. the half attached to the moving platen.We have stated previously that we need to eject the molding from the core and it therefore follows that the core,too,will most satisfactorily be located in the moving half.The ejector system in a mould will be discussed under three headings,namely:(ⅰ)the ejector grid;(ⅱ)the ejector plate assembly; and(ⅲ)the method of ejection.5.1、Ejector gridThe ejector grid(Figure5-1)is that part of the mould which supports the mould plate and provides a space into which theejector plate assembly can be fitted and operated.The grid normally consists of a back plate on to which is mounted a number of conveniently shaped “support blocks”.The ejector plate assembly is that part of the mould to which the ejector element is attached.The assembly is contained in a pocket,formed by the ejector grid,directly behind the mould plate.The assembly(Figure5-2)consists of an ejector plate,a retaining plate and an ejector rod.One end of this latter member is threaded and it is screwed into the ejector plate.In this particular design the ejector rod function not only as an actuating member but also as a method of guiding the assembly.Note that the parallel portion of the ejector rod passes through an ejector rod bush fitted in the back plate of the mould.5.2、Ejection techniquesWhen a molding cools,it contracts by an amount depending on the material being processed.For a molding which has no internal form,for example,a solid rectangular block,the molding will shrink away from the cavity walls,thereby permitting a simple ejection technique to be adopted.However,when the molding has internal form,the molding,as it cools,will shrink onto the core and some positive type of ejection is necessary.The designer has several ejection techniques from which to choose,but in general,the choice will be restricted depending upon the shape of the molding.The basic ejection techniques are as follows:(ⅰ)pin ejection(ⅱ)sleeve ejection(ⅲ)stripper plate ejection and(Ⅳ)air ejection.Figure 2-1aFigure 2-1bFigure 3-1Figure 3-2Figure 4-1aFigure 4-1bFigure 5-1Figure 5-2注塑模1、注塑模尽管成型某些热固性材料的方法取得了一定的进步,但注塑模主要(还是)用来生产热塑性塑件。
注塑模具设计英文参考文献
Injection molding die design is a crucial aspect of the manufacturing process to produce high-quality plastic products. Various technical references have been published over the years, providing valuable insights into the design principles, strategies, and best practices related to injection molding die design. Here are some key references that can be used as a starting point for further exploration:1.Injection Mold Design Engineering (David O. Kazmer, 2011) This bookprovides a comprehensive overview of injection mold design, covering topics such as mold geometry, gating systems, cooling and heating, ejector systems, and mold materials. It also discusses the analysis and optimization of molddesigns using computer-aided engineering tools.2.Injection Molds and Molding: A Practical Manual (Jiri Karasek, 2006)This practical manual offers a step-by-step guide to injection mold design and production. It covers various aspects of mold design, including cavity and core geometry, runner systems, venting, cooling, ejection, and mold materials. The book also addresses common design challenges and troubleshootingtechniques.3.Plastic Injection Molding: Manufacturing Process Fundamentals(Douglas M. Bryce and Charles A. Daniels, 2014) This reference provides an in-depth understanding of the injection molding process and its fundamentals. It discusses the principles of mold design, material selection, process parameters, molding defects, and mold maintenance. The book emphasizes the importance of considering the design-for-manufacturability aspect in mold design.4.Mold Design Using SolidWorks (Edward J. Bordin, 2010) Focused onmold design using SolidWorks software, this book provides practical insights into mold design methodology, including parting line creation, runner system design, cooling strategies, and mold analysis. It also covers advanced topicssuch as hot runner systems and side actions.5.Designing Injection Molds for Thermoplastics (H.T. Rowe, 2010) Thiscomprehensive reference addresses the design considerations specific tothermoplastic injection molds. It covers mold configuration, gating design,cooling strategies, shrinkage and warpage control, and mold materials. Thebook also includes case studies and practical tips for mold design optimization.6.Mold-Making Handbook (Kurtz Ersa Corporation, 2009) Thishandbook offers practical advice on mold design, construction, andmaintenance. It covers topics like mold steel selection, surface finishing, cavity design, cooling channels, ejection systems, and high-precision molding. Thereference provides insights into the latest developments in mold-makingtechnology.These references provide a solid foundation for understanding injection mold design principles, methodologies, and considerations. Additionally, industrypublications, research papers, and case studies can offer further insights into specific design aspects, material selection, and advanced techniques. It is important to consult multiple sources and stay updated with the latest trends and advancements in injection mold design to ensure efficient and robust manufacturing processes.。
注塑模具原理与基本方法外文文献翻译、中英文翻译
外文资料翻译资料来源:文章名:Tribological assessment of the interface injection mold/plastic part 书刊名:tribology international作者:crossmark出版社:journal homepage文章译名:注塑模具原理及基本方法姓名:学号:指导教师(职称):专业:班级:所在学院:外文原文:The sector of plastics processing is relatively young compared to cast iron, steel or glass industry. So it still has a very strong development potential. One of the current challenges of the plastic injection process is linked to the importance given to product design that enables a strong differentiation[1]. Plastic parts with an increased technical level of surface accuracy are required in the areas of luxury, packaging, automotive, including the medical and optics. Their development involves the improvement of the fabrication process, and one of the keys lies in the mastery of the surface conditions of the molds.Injection molding is a cyclic process, characterized by 5 phases: dosing, injection, packing, cooling and ejection . The raw material that is dosed in the machine must be pure and conserved before use at an adequate temperature in order to be as dried as possible. This is necessary to avoid condensation inside the mold. The injection phase is characterized by high fl ow rates and hence high shear rate (tangential effect). As the molten material enters the mold, two heat transfer mechanisms occur: convection (between the melted material and mold surface) and viscous dissipation (due to the effect of injection speed on the injected material viscosity). As the fi lling is complete, the mold is uphold at a predetermined pressure and so the packing phase is initiated. During this phase, the molten polymer continues to be introduced into the mold to compensate for the shrinkage of the already injected material as it cools down. After a speci fi c time, the cooling phase (contrary to the cooling state which begins during injection and packing phase) of the entire assembly starts and so also the solidi fi cation process of the plastic part. As the material solidi fi es and shrinks in the mold, the dominant heat transfer mechanism is conduction. When the part is suf fi cient solidi fi ed, it is ejected from the mold. During this last phase, a normal effect can be attributed to the ejection force and adhesion phenomena can occur between the mold surface and the plastic part[2].Despite the undeniable diversity of con fi gurations available (in terms of combination: mold material, surface fi nish and processed materials), the producers are faced with similar dif fi culties. Thus, the key shortcomings that stand out, more or less combined, can be summarize as follows:●t he fouling phenomena which require frequent stops for cleaning;●c orrosion phenomena that can greatly limit the lifetime of the mold cavity as a function of the type of injected polymer;●p roblems of sticking and releasing in function of the injected materials and surface quality;●p roblems in keeping the polishing quality;●s cratches or shocks during use or storage.The available literature approaches experimental and/or numerical, various aspects regarding the plastic injection molding process. One of them is the fi lling and fl ow behavior of molten polymers.[3]Bociaga and Jaruga studied the formation of fl ow, weld and meld lines by developing a new method of fl ow visualization, which can prove helpful in the identi fi cation of weakareas on injected parts. Also the effect of pressure and cavity thickness were assessed. Same topic was treated by Ozdemir etal.[4],comparing the behavior of molten HDPE (high density poly-ethylene) and PE experimentally and numerically.During molding, friction forces act fi rst between the mold surface and the molten polymer and second when the plastic part is ejected from the mold. Bull etal.[5] adapted the ASTM rubber wheel abrasion test to simulate the conditions of wear produced by the glass fi lled polymers on the barrel surface of an injection molding machine. Various coatings were tested, but unfortunately they tended to have a weak performance on account of the test conditions.[6] developed a prototype apparatus to study the friction properties of molding thermoplastics during ejection phase. The measured friction coef fi cient had a tendency to increase with the roughness. But when the roughness was reduced the friction coef fi cient increase due to the rising adhesion forces effect. The scanning electron microscopy images of the mold surface and the ones for the polycarbonate (PC) and polypropylene (PP) plastic parts, revealed a clear replication of the mold surface on the parts.Transient in nature, injection molding process involves not only several heat transfer mechanisms, phase change and time varying boundary conditions, but goes further in adding the effect of material properties and geometry of the injected part.[7] Bendada etal performed a study to evaluate the nature of thermal contact between polymer and mold through the different phases of a typical injectioncycle. Their fi ndings concluded that the thermal contact resistance was not negligible, not constant with time and was strongly linked with the process conditions.The existing number of studies concerning the phenomena present at the interface mold surface/polymer is relatively low to other related topics. Besides, they don’t focus on studying the current limitations of the plastic injection process at a microscopic scale, taking into account various macroscopic in fl uences. To overcome plastic injection molding shortcomings, the contact conditions at the interface between mold surface and plastic part have to be identi fi ed. This work focus on the effect of the polishing quality, the mold geometry and the injected material on that interface, by studying the corrosion-mechanical attack and the mechanical -physical- chemical one.2. Method and materials2.1. MaterialsFour polymers were chosen to be injected: ionomer resin (E-MMA Surlyn s PC 2 000), styrene-acrylonitrile resin (SAN Tyril 790), polyamide with 25% glass fi bers (PA66GF25) and poly-carbonate (PC Makrolon LQ 2647). Surlyn is a copolymer of ethylene and methacrylic acid where some of the acid groups are neutralized to form the sodium salt. The acid in the polymer gives polarity and reduces crystallinity. The ionic bonding between the polymer chains gives outstanding melt strength, toughness and clarity. The reason of choosing Surlyn was based on the experience of our industrial partners, which fi nd it particularly corrosive despite its good properties. Surlyn is also a copolymer, optically transparent and brittle in mechanical behavior. It's considered in this study a reference material, usually used in cosmetics, luxury and automobile domains. PA66GF25 is an aliphatic-polyamide, reinforced with 25% glass fi bers. PA66 has an excellent balance of strength, ductility and heat resistance. The glass fi bers exert an abrasive effect and thus affect the mechanical protection of the polishing. PC is composed by carbonate groups. It has a high impact-resistance, low scratch-resistance and is highly transparent to visible light. It is usually used for the production of eyewear lenses and exterior automotive components.2.2. MoldsTwo molds, made of hardened steel (52 HRC) containing 13% to 15% ofChromium, with different geometries were used, one with a mirror polished surface (complex geometry) and another with an optical polished surface (simple geometry) . The mold has two parts: the stamp and the matrix. For the mold with complex geometry the stamp is of 149 119 80 mm in size and the matrix of 149 119 50 mm. In case of the one with a simple geometry, the stamp is of 50 70 mm in size and the matrix has a cylinder form with a diameter of 70 mm. The surface fi nish of the mirror and optical polished molds involved a polishing cloth and diamond paste. Further details on the polishing process are con fi dential.The mirror polished mold was specially designed for this study by Technimold (a mold maker) to highlight the role of angles and obstacles in the formation of defaults. Also the mold design did not include a special feature that can evacuate the air. This was done intentionally in order to submit the polished surfaces to aggressive conditions. The molding process was performed at “Center Technique dela Plasturgie et des Composites”(IPC, France) on a 50 T Engel machine. The injection parameters, listed in Table 2, were chosen in accordance with standard speci fi cations for the injected polymers. Based on a numerical simulation they were adapted to respond in conformity with the mold design. Two injection campaigns were conducted on this type of mold. After the fi rst campaign, on the plane part of the mold stamp, an insert with a diameter of 12 mm and a height of 8 mm, was mounted to facilitate the morphology assessment.For the Surlyn injection, 3000 parts were injected in the fi rst campaign. After surface analysis, the mold was submitted to the industrial cleaning operation. The second campaign consisted in the injection of 3700 more parts. SAN and PA66GF25 were injected on the same mold. During the fi rst campaign, only 8000 SAN parts were injected. Before starting a second campaign, the mold was polished entirely. The second campaign consisted in the injection of 300 parts of SAN. The insert was changed before starting the injection of 12 200 PA66GF25 parts.2.3. MethodThe surface expertize consisted in two main steps: the microscopy analysis and the inter ferometry measurements before and after injection process. Due to their large dimensions and elevated mass, the surface analysis of the mirror polished molds was per-formed using a classic optical microscope. For the optical polished one, thanks to smaller dimensions, the microscope analysis could be carried out using a numerical optical microscope (Keyence) and a high resolution environmental scanning electron microscope (FEI XL30 ESEM). Although two injection campaigns have been performed, the results presented in this paper, refer only to the surface expertize performed at the end of the second campaign. For the injected plastic parts, only the interface between mold matrix plane part and plastic part is discussed in this paper.In order to identify the chemical composition of different deposits found on the mirror polished mold surfaces, a Fourier Transform Infrared (FTIR) spectrometer was used for the analysis.3. Results and discussions3.1. Mirror polished mold3.1.1. Injection Surlyn sAll along the stamp plane part, deposits different in texture and consistence can be observed (Fig. 5). Their location and morphologyseem to indicate the fl ow direction of the molten polymer. Also it can be noticed, towards the end of the fl ow, the deposits grow in terms of thickness and occupied surface.The type of deposit observed in Fig. 5e and f is also observed after the fi rstinjection campaign (3000 injected parts), and appeared that the cleaning operation has been able to remove it, but formed again during the second injection campaign (3700 injected parts). This particular deposit is located between the extremity of the oval bump and the hole where one of the ejection pins acts. Also in this location the fl ow changes direction, more precisely makes a left turn; fact also revealed by the deposit morphology. Its existence can be explained starting with the effect of the injection speed on the molten polymer viscosity, which is considered to be a heat transfer mechanism that occurs during the injection process. Due to the geometry factor, the viscous dissipation creates a temperature gradient which sensitizes this area. During the packing phase, as the mold continues to be fi lled, the location identi fi ed is one of the last to be reached by the molten polymer. As the holding phase begins and with it the solidi fi cation, the temperature gradient that appears in the injection phase continues to act and by doing so it delays the solidi fi cation in this area. When the established time for the holding phase expires, the mechanism of ejection is set in motion. The ejection pin is close to the identi fi ed location and as it was affected by the temperature gradient and has not yet been entirely solidi fi es, it will also be the fi rst area to be separated from the mold surface. All these can explain the appearance of the adhesion phenomenon.In the deposit appears like a thin fi lm and is also located in an area where the fl ow changes direction. It could also be justi fi ed by the temperature gradient, but its aspect and composition suggest that may another phenomena can occur. The infrared analysis performed on this area suggest that only some of the wave numbers match with the ones from the spectrum registered for the injected part It is possible that the gases released from the contact of the molten polymer with the mold surface reacted with the additives from the raw material composition and facilitated the separation of the thin layer that stick on the mold surface. Also the “scraped” aspect of this deposit indicates that is more likely that this type of deposit has formed during the injection phase.Holes (form 14.6nm to 404nm deep) are observed before injection probably due to polishing.Their morphology evolves during injection process:the holes expand in occupation area and depth(39.7nm to 877nm).the pointing red arrows indicate the presence of the evolved holes.They exhibit two types of morphology.The first type illustrated shows very small holes focused altogether in smaller or larger spots and the second type illustrated presents a hole surrounded by a “cloud” of small holes.Due to the inclusions in the bulk material,grains dislocation could occur causing the formation of holes during polishing process.Those holes are modified in term of depth and area during injection process.As reported,stress corrosion cracking can affect the molds,starting at a microscopic level and revealing itself at crack.The primary causal elements are the metallurgy of steel,the presence of chlorine in the water used in the cooling lines of the mold and the stresses on the tool during molding.It is known that Chromium gives the steel corrosion resistance,by providing a protective oxide layer.Thus it is possible that due to the polishing defects(holes),the thickness of the layer is compromised and thus when a high viscous corrosive polymer,like Surlyn,is injected,the areas affected by holes,are submitted to corrosion nature of Surlyn(based on the experience of industrial project partners),can create an aggressive environment at the mold/molten polymer interface due to the gases release.The high viscosity of Surlyn and its capability to stick onto the mold surface also plays a role in terms of exerting a mechanical-physico-chemical attack on the area where the defaults are located.All these statements allow to catalog this default as corrosion pit.4.ConclusionsThis study has allowed the identification and evaluation of defaults that occur during plastic injection process,at microscopic scale.The results obtained highlight the different damage mechanisms sustained by the mold surface,as a function of polishing,geometry and injected material.It can be also observed that for each material injected there is a difference of level of wear and damage mechanism between the stamp and the matrix.Surlyn injection exhibited considerable amount of deposits on the mold stamp.It seems that the physico-chemical conditions,created during the injection by this type polymer,favored the adhesion.Also in the case ,the coupling effects of polishing quality,the injected material,adhesion and the lack of the mold feature that evacuates air,tend to form corrosion pits on a mirror polished surface.SAN and PA66GF25 polymers were injected successively on the samemold.The mold surface presented polishing defaults(holes)before injection.The holes were enlarged in the direction perpendicular to the injection flow due to abrasive effect of glass fibers.A critical characterization of the mold surface topography was performed in order to identify the location and the type of defaults that occur when more or less aggressive material were injected in molds with different geometries.All the results provided can be taken into consideration for the design of a “chameleon” coating that can overcome present drawback.注塑模具原理与基本方法译文:与铸铁、钢铁或玻璃工业相比,塑料加工行业相对年轻。
注塑模具设计与制造外文文献翻译
2 Injection molding machineFrom Plastics Wiki, free encyclopediaInjection molding machines consist of two basic parts, an injection unit and a clamping unit. Injection molding machines differ in both injection unit and clamping unit. The name of the injection molding machine is generally based on the type of injection unit used.2.1Types of injection molding machinesMachines are classified primarily by the type of driving systems they use: hydraulic, electric, or hybrid.2.1.1HydraulicHydraulic presses have historically been the only option available to molders until Nissei Plastic Industrial Co., LTD introduced the first all-electric injection molding machine in 1983. The electric press, also known as Electric Machine Technology (EMT), reduces operation costs by cutting energy consumption and also addresses some of the environmental concerns surrounding the hydraulic press.2.1.2ElectricElectric presses have been shown to be quieter, faster, and have a higher accuracy, however the machines are more expensive.2.1.3HybridHybrid injection molding machines take advantage of the best features of both hydraulic and electric systems. Hydraulic machines are the predominant type in most of the world, with the exception of Japan.2.2Injection unitThe injection unit melts the polymer resin and injects the polymer melt into the mold. The unit may be: ram fed or screw fed.The ram fed injection molding machine uses a hydraulically operated plunger to push the plastic through a heated region. The high viscosity melt is then spread into a thin layer by a "torpedo" to allow for better contact with the heated surfaces. The melt converges at a nozzle and is injected into the mold.Reciprocating screw A combination melting, softening, and injection unit in an injection molding machine. Another term for the injection screw. Reciprocating screws are capable of turning as they move back and forth.The reciprocating screw is used to compress, melt, and convey the material. The reciprocating screw consists of three zones (illustrated below):•feeding zone•compressing zone•metering zoneWhile the outside diameter of the screw remains constant, the depth of the flights on the reciprocating screw decreases from the feed zone to the beginning of the metering zone. These flights compress the material against the inside diameter of the barrel, which creates viscous (shear) heat. This shear heat is mainly responsible for melting the material. The heater bands outside the barrel help maintain the material in the molten state. Typically, a molding machine can have three or more heater bands or zones with different temperature settings.Injection molding reciprocating screw An extruder-type screw rotates within a cylinder, which is typically driven by a hydraulic drive mechanism. Plastic material is moved through the heated cylinder via the screw flights and the material becomes fluid. The injection nozzle is blocked by the previous shot, and this action causes the screw to pump itself backward through the cylinder. (During this step, material is plasticated and accumulated for the next shot.) When the mold clamp has locked, the injection phase takes place. At this time, the screw advances, acting as a ram. Simultaneously, the non-return valve closes off the escape passages in the screw and the screw serves as a solid plunger, moving the plastic ahead into the mold. When the injection stroke and holding cycle is completed, the screw is energized to return and the non-return valve opens, allowing plastic to flow forward from the cylinder again, thus repeating the cycle.2.2.1Feed hopperThe container holding a supply molding material to be fed to the screw. The hopper located over the barrel and the feed throat connects them.2.2.2Injection ramThe ram or screw that applies pressure on the molten plastic material to force it into the mold cavities.2.2.3Injection screwThe reciprocating-screw machine is the most common. This design uses the same barrel for melting and injection of plastic.The alternative unit involves the use of separate barrels for plasticizing and injecting the polymer. This type is called a screw-preplasticizer machine or two-stage machine. Plastic pellets are fed from a hopper into the first stage, which uses a screw to drive the polymer forward and melt it. This barrel feeds a second barrel, which uses a plunger to inject the melt into the mold. Older machines used one plunger-driven barrel to melt and inject the plastic. These machines are referred to as plunger-type injection molding machines.2.2.4BarrelBarrel is a major part that melts resins transmitted from hopper through screws and structured in a way that can heat up resins to the proper temperature. A band heater, which can control temper atures in five sections, is attached outside the barrel. Melted resins are supplied to the mold passing through barrel head, shot-off nozzle, and one-touch nozzle.2.2.5Injection cylinderHydraulic motor located inside bearing box, which is connected to injection cylinder load, rotates screw, and the melted resins are measures at the nose of screw. There are many types of injection cylinders that supply necessary power to inject resins according to the characteristics of resins and product types at appropriate speed and pressure. This model employs the double cylinder type. Injection cylinder is composed of cylinder body, piston, and piston load.2.3Clamping unitThe clamping unit holds the mold together, opens and closes it automatically, and ejects the finished part. The mechanism may be of several designs, either mechanical, hydraulic or hydromechanical.Toggle clamps - a type clamping unit include various designs. An actuator moves the crosshead forward, extending the toggle links to push the moving platen toward a closed position. At the beginning of the movement, mechanical advantage is low and speed is high; but near the end of the stroke, the reverse is true. Thus, toggle clamps provide both high speed and high force at different points in the cycle when they are desirable. They are actuated either by hydraulic cylinders or ball screws driven by electric motors. Toggle-clamp units seem most suited to relatively low-tonnage machines.Two clamping designs: (a) one possible toggle clamp design (1) open and (2) closed; and (b) hydraulic clamping (1) open and (2) closed. Tie rods used to guide movuing platens not shown.Hydraulic clamps are used on higher-tonnage injection molding machines, typically in the range 1300 to 8900 kN (150 to 1000 tons). These units are also more flexible than toggle clamps in terms of setting the tonnage at given positions during the stroke.Hydraulic Clamping System is using the direct hydraulic clamp of which the tolerance is still and below 1 %, of course, better than the toggle system. In addition, the Low Pressure Protection Device is higher than the toggle system for 10 times so that the protection for the precision and expensive mold is very good. The clamping force is focus on the central for evenly distribution that can make the adjustment of the mold flatness in automatically. Hydromechanical clamps -clamping units are designed for large tonnages, usually above 8900 kN (1000 tons); they operate by (1) using hydraulic cylinders to rapidly move the mold toward closing position, (2) locking the position by mechanical means, and (3) using high pressure hydraulic cylinders to finally close the mold and build tonnage.2.3.1Injection moldThere are two main types of injection molds: cold runner (two plate and three plate designs) and hot runner– the more common of the runnerless molds.2.3.2Injection platensSteel plates on a molding machine to which the mold is attached. Generally, two platens are used; one being stationary and the other moveable, actuated hydraulically to open and close the mold. It actually provide place to mount the mould. It contains threaded holes on which mould can be mounted using clamps.2.3.3Clamping cylinderA device that actuates the chuck through the aid of pneumatic or hydraulic energy.2.3.4Tie BarTie bars support clamping power, and 4 tie bars are located between the fixing platen and the support platen.3 Injection mouldFrom Wikipedia, the free encyclopediaMold A hollow form or cavity into which molten plastic is forced to give the shape of the required component. The term generally refers to the whole assembly of parts that make up the section of the molding equipment in which the parts are formed. Also called a tool or die. Moulds separate into at least two halves (called the core and the cavity) to permit the part to be extracted; in general the shape of a part must be such that it will not be locked into the mould. For example, sides of objects typically cannot be parallel with the direction of draw (the direction in which the core and cavity separate from each other). They are angled slightly; examination of most household objects made from plastic will show this aspect of design, known as draft. Parts that are "bucket-like" tend to shrink onto the core while cooling and, after the cavity is pulled away, are typically ejected using pins. Parts can be easily welded together after moulding to allow for a hollow part (like a water jug or doll's head) that couldn't physically be designed as one mould.More complex parts are formed using more complex moulds, which may require moveable sections, called slides, which are inserted into the mould to form particular features that cannot be formed using only a core and a cavity, but are then withdrawn to allow the part to be released. Some moulds even allow previously moulded parts to be re-inserted to allow a new plastic layer to form around the first part. This system can allow for production of fully tyred wheels.Traditionally, moulds have been very expensive to manufacture; therefore, they were usually only used in mass production where thousands of parts are being produced.Molds require: Engineering and design, special materials, machinery and highly skilled personnel to manufacture, assemble and test them.Cold-runner moldCold-runner mold Developed to provide for injection of thermoset material either directly into the cavity or through a small sub-runner and gate into the cavity. It may be compared to the hot-runner molds with the exception that the manifold section is cooled rather than heated to maintain softened but uncured material. The cavity and core plates are electrically heated to normal molding temperature and insulated from the cooler manifold section.3.1.1Types of Cold Runner MoldsThere are two major types of cold runner molds: two plate and three plate.3.1.2Two plate moldA two plate cold runner mold is the simplest type of mold. It is called a two plate mold because there is one parting plane, and the mold splits into two halves. The runner system must be located on this parting plane; thus the part can only be gated on its perimeter.3.1.3Three plate moldA three plate mold differs from a two plate in that it has two parting planes, and the mold splits into three sections every time the part is ejected. Since the mold has two parting planes, the runner system can be located on one, and the part on the other. Three plate molds are used because of their flexibility in gating location. A part can be gated virtually anywhere along its surface.3.1.4AdvantagesThe mold design is very simple, and much cheaper than a hot runner system. The mold requires less maintenance and less skill to set up and operate. Color changes are also very easy, since all of the plastic in the mold is ejected with each cycle.3.1.5DisadvantagesThe obvious disadvantage of this system is the waste plastic generated. The runners are either disposed of, or reground and reprocessed with the original material. This adds a step in the manufacturing process. Also, regrind will increase variation in the injection molding process, and could decrease the plastic's mechanical properties.3.1.6Hot runner moldHot-runner mold -injection mold in which the runners are kept hot and insulated from the chilled cavities. Plastic freezeoff occurs at gate of cavity; runners are in a separate plate so they are not, as is the case usually, ejected with the piece.Hot runner molds are two plate molds with a heated runner system inside one half of the mold.A hot runner system is divided into two parts: the manifold and the drops. The manifold has channels that convey the plastic on a single plane, parallel to the parting line, to a point abovethe cavity. The drops, situated perpendicular to the manifold, convey the plastic from the manifold to the part.3.1.7Types of Hot Runner MoldsThere are many variations of hot runner systems. Generally, hot runner systems are designated by how the plastic is heated. There are internally and externally heated drops and manifolds.3.1.8Externally heated hot runnersExternally heated hot runner channels have the lowest pressure drop of any runner system (because there is no heater obstructing flow and all the plastic is molten), and they are better for color changes none of the plastic in the runner system freezes. There are no places for material to hang up and degrade, so externally heated systems are good for thermally sensitive materials.3.1.9Internally heated hot runnersInternally heated runner systems require higher molding pressures, and color changes are very difficult. There are many places for material to hang up and degrade, so thermally sensitive materials should not be used. Internally heated drops offer better gate tip control. Internally heated systems also better separate runner heat from the mold because an insulating frozen layer is formed against the steel wall on the inside of the flow channels.3.1.10 insulated hot runnersA special type of hot runner system is an insulated runner. An insulated runner is not heated; the runner channels are extremely thick and stay molten during constant cycling. This system is very inexpensive, and offers the flexible gating advantages of other hot runners and the elimination of gates without the added cost of the manifold and drops of a heated hot runner system. Color changes are very easy. Unfortunately, these runner systems offer no control, and only commodity plastics like PP and PE can be used. If the mold stops cycling for some reason, the runner system will freeze and the mold has to be split to remove it. Insulated runners are usually used to make low tolerance parts like cups and frisbees.3.1.11 DisadvantagesHot-runner mold is much more expensive than a cold runner, it requires costly maintenance, and requires more skill to operate. Color changes with hot runner molds can be difficult, since it is virtually impossible to remove all of the plastic from an internal runner system.3.1.12 AdvantagesThey can completely eliminate runner scrap, so there are no runners to sort from the parts, and no runners to throw away or regrind and remix into the original material. Hot runners are popular in high production parts, especially with a lot of cavities.Advantages Hot Runner System Over a Cold Runner System include:•no runners to disconnect from the molded parts•no runners to remove or regrind, thus no need for process/ robotics to remove them•having no runners reduces the possibility of contamination•lower injection pressures•lower clamping pressure•consistent heat at processing temperature within the cavity•cooling time is actually shorter (as there is no need for thicker, longer-cycle runners)•shot size is reduced by runner weight•cleaner molding process (no regrinding necessary)•nozzle freeze and sprue sticking issues eliminated中文翻译注塑模具设计与制造2 注射机选自《维基百科》注射机由两个基本部分组成,注射装置和夹紧装置。
注塑模具设计技术中英文对照外文翻译文献
中英文资料对照外文翻译英文:Design and Technology of the Injection Mold1、3D solid model to replace the center layer modelThe traditional injection molding simulation software based on products of the center layer model. The user must first be thin-walled plastic products abstract into approximate plane and curved surface, the surface is called the center layer. In the center layer to generate two-dimensional planar triangular meshes, the use of these two-dimensional triangular mesh finite element method, and the final result of the analysis in the surface display. Injection product model using3D solid model, the two models are inconsistent, two modeling inevitable. But because of injection molding product shape is complex and diverse, the myriads of changes from athree-dimensional entity, abstraction of the center layer is a very difficult job, extraction process is very cumbersome and time-consuming, so the design of simulation software have fear of difficulty, it has become widely used in injection molding simulation software the bottleneck.HSCAE3D is largely accepted3D solid / surface model of the STL file format. Now the mainstream CAD/CAM system, such as UG, Pro/ENGINEER, CATIA and SolidWorks, can output high quality STL format file. That is to say, the user can use any commercial CAD/CAE systems to generate the desired products3D geometric model of the STL format file, HSCAE3D can automatically add the STL file into a finite element mesh model, through the surface matching and introduction of a new boundary conditions to ensure coordination of corresponding surface flow, based on3D solid model of analysis, and display of three-dimensional analysis results, replacing the center layer simulation technology to abstract the center layer, and then generate mesh this complicated steps, broke through system simulation application bottlenecks, greatly reducing the burden of user modeling, reduces the technical requirement of the user, the user training time from the past few weeks shorter for a fewhours. Figure 1 is based on the central layer model and surface model based on 3D solid / flow analysis simulation comparison chart.2、Finite element, finite difference, the control volume methodsInjection molding products are thin products, products in the thickness direction of size is much smaller than the other two dimensions, temperature and other physical quantities in the thickness direction of the change is very large, if the use of a simple finite element and finite difference method will cause analysis time is too long, can not meet the actual needs of mold design and manufacturing. We in the flow plane by using finite element method, the thickness direction by using finite difference method, were established and plane flow and thickness directions corresponding to the size of the grid and coupling, while the accuracy is guaranteed under the premise of the calculation speed to meet the need of engineering application, and using the control volume method is solved. The moving boundary problem in. For internal and external correspondence surface differences between products, can be divided into two parts the volume, and respectively formed the control equation, the junction of interpolation to ensure thatthe two part harmony contrast.3、Numerical analysis and artificial intelligence technologyOptimization of injection molding process parameters has been overwhelming majority of mold design staff concerns, the traditional CAE software while in computer simulation of a designated under the conditions of the injection molding conditions, but is unable to automatically optimize the technical parameters. Using CAE software personnel must be set to different process conditions were multiple CAE analysis, combined with practical experience in the program were compared between, can get satisfactory process scheme. At the same time, the parts after the CAE analysis, the system will generate a large amount of information about the project ( product, process, analyzes the results ), which often results in a variety of data form, requiring the user to have the analysis and understanding of the results of CAE analysis ability, so the traditional CAE software is a kind of passive computational tools, can provide users with intuitionistic, effective engineering conclusion, to software users demand is too high, the influence of CAE system in the larger scope of application and popularization. In view of the above, HSCAE3D software in the original CAE system based on accurate calculationfunction, the knowledge engineering technology is introduced the system development, the use of artificial intelligence is the ability of thinking and reasoning, instead of the user to complete a large number of information analysis and processing work, directly provide guiding significance for the process of conclusions and recommendations, effectively solve the CAE of the complexity of the system and the requirements of the users of the contradiction between, shortening of the CAE system and the distance between the user, the simulation software by traditional " passive" computational tools to " active" optimization system. HSCAE3D system artificial intelligence technology will be applied to the initial design, the results of the analysis of CAE interpretation and evaluation, improvement and optimization analysis of3 aspects.译文:注塑模具设计的技术1.用三维实体模型取代中心层模型传统的注塑成形仿真软件基于制品的中心层模型。
注塑模具 外文文献
International Journal of Automotive Technology , Vol. 13, No. 2, pp. 273−277 (2012)DOI 10.1007/s12239−012−0024−5Copyright ©2012KSAE/063−11pISSN 1229−9138/eISSN 1976-3832273DESIGN OPTIMIZA TION OF AN INJECTION MOLD FOR MINIMIZING TEMPERA TURE DEVIA TIONJ.-H. CHOI 1), S.-H. CHOI 1), D. PARK 2), C.-H. PARK 2), B.-O. RHEE 1)* and D.-H. CHOI 2)1)Graduate School of Mechanical Engineering, Ajou University, Gyeonggi 443-740, Korea 2)Graduate School of Mechanical Engineering, Hanynag University, Seoul 133-791, Korea(Received 24 January 2011; Revised 15 June 2011; Accepted 17 June 2011)ABSTRACT −The quality of an injection molded part is largely affected by the mold cooling. Consequently, this makes it necessary to optimize the mold cooling circuit when designing the part but prior to designing the mold. V arious approaches of optimizing the mold cooling circuit have been proposed previously. In this work, optimization of the mold cooling circuit was automated by a commercial process integration and design optimization tool called Process Integration, Automation and Optimization (PIAnO), which is often used for large automotive parts such as bumpers and instrument panels. The cooling channels and baffle tubes were located on the offset profile equidistant from the part surface. The locations of the cooling channels and the baffle tubes were automatically generated and input into the mold cooling computer-aided engineering program, Autodesk Moldflow Insight 2010. The objective function was the deviation of the mold surface temperature from a given design temperature. Design variables in the optimization were the depths, distances and diameters of the cooling channels and the baffle tubes. For a more practical analysis, the pressure drop and temperature drop were considered the limited values. Optimization was performed using the progressive quadratic response surface method. The optimization resulted in a more uniform temperature distribution when compared to the initial design, and utilizing the proposed optimization method, a satisfactory solution could be made at a lower cost.KEY WORDS :Injection molding, Cooling channel, Cooling analysis, PQRSM, Design optimization1. INTRODUCTIONThe cooling stage is the longest stage during the cycle time of the injection molding process. Therefore, the most effective method to reduce the cycle time is to reduce the cooling time. The cooling time is fundamentally determined by the part thickness and mold temperature, which creates a cooling time limitation. If the mold temperature and part thickness are uniform over a whole part, the cooling time is not a concern; however, non-uniform part thickness and mold temperature distribution lengthen the overall cooling time. A longer cooling time means poor temperature uniformity, which can cause the part to warp. This is especially true for large products, such as automotive bumpers and instrument panels. It is for these types of parts that temperature uniformity becomes the most important factor in mold design.We developed an automated optimization of the cooling circuit for an early part design in order to check the design validity. Usually the early part design is checked by the filing/packing and warpage analyses without a cooling analysis. This is because the assumption is that the mold temperature is uniform, which is not actually true.Providing a rapidly optimized cooling circuit for the designed part would help part designers correct their design (Koresawa and Suzuki, 1999).The optimization was designed to minimize the part temperature deviation using design variables such as the diameters and distances of the cooling channels and baffle tubes and the depths of the part from the mold surface of the cooling channels and baffle tubes. A commercial computer-aided engineering (CAE) tool, Autodesk Moldflow Insight,was used for the cooling analysis. We successfully obtained an optimized cooling circuit in a time much shorter than can be achieved in a manual design. In order to develop the automated optimization of the cooling circuit for the practical mold design, practical design parameters such as the pressure drop limit and the coolant temperature rise were considered in the optimization.The performance of the optimization technique can be affected by numerical noise in the responses. To find an optimum solution effectively when numerical noise exists,we performed an optimization by applying a regression-based sequential approximate optimizer known as the Progressive Quadratic Response Surface Method (PQRSM)(Hong e t al ., 2000), which was part of a commercial process integration and design optimization (PIDO) tool known as the Process Integration, Automation and Optimization (PIAnO) (FRAMAX, 2009).*Corresponding author . e-mail: rhex@ajou.ac.kr274J.-H. CHOI et al.2. MODEL AND CHANNEL CONFIGURATION2.1. Model ConfigurationThe model used for the optimization and CAE analysis was an automotive front bumper (FB). The size of the part was 1,800×600 mm, the element type was triangular and the number of elements in the model was approximately 26,000, with an average aspect ratio of 1.5. The model is shown in Figure 1.2.2. Cooling Channel ConfigurationThe cooling circuit for the automotive bumper mold is typically designed to have a horizontal plane of line cooling channels and to install baffle tubes from the line cooling channels. However, in this design, unnecessarily long baffle tubes attached at a line cooling channel may cause a high pressure drop in the cooling channel. The line cooling channels may not contribute to mold cooling due to their large distance from the part surface. In order to improve the design, the line cooling channels were located along the offset profile of the part surface as shown in Figure 2. The end points of the baffle tubes were also located on the offset profile along a line cooling channel.Either the line cooling channels or baffle tubes were located on the offset profiles with equal arc distances between them.3. FORMULATION3.1. Design ConstraintsThe limitation of the pressure drop and the temperature rise between the inlet and outlet of cooling channel should also be considered in the design of the mold cooling circuit. A high pressure drop usually occurs in a needlessly longcooling circuit. In a long cooling circuit, the flow rate of coolant is low, which results in a high mold temperature and a high temperature rise at the outlet. The design defect could eventually be found in the cooling analysis; however,the optimization is already time consuming, so it is better to instead apply the limits as constraints in the optimization. In this work we assumed that 4 line cooling channels were connected in series as a cluster, as shown in Figure 3.Clusters are connected in parallel by a manifold. Usually,the maximum pressure drop in a cluster is limited to 200kPa, and the maximum temperature rise at the outlet is 5o C (Menges e t al ., 2001). In the cooling analysis, each line cooling channel is regarded as a separate independent circuit for convenience. Because there were 4 line cooling channels in a circuit, the limits on the pressure drop and the temperature rise in each line cooling channel were 50 kPa and 1.25o C, respectively. We also have an additional constraint due to the fact that the diameter of the baffle tube must be greater than or equal to the diameter of the cooling channel because the baffle tube has lower heat removal efficiency than the cooling channel. These three design constraints can be expressed as Equations (1), (2) and (3) ,(1),(2),(3)where G 1 is the constraint on pressure drop, G 2 is the constraint on temperature rise, and G 3 represents the subtraction of the diameter of the baffle tube from the diameter of the cooling channel.3.2. Design V ariablesIn this work, the diameters, distances and depths of the line cooling channels and baffle tubes were chosen as design variables for optimization. The total number of design variables was 6 as shown in Table 1. Typically, the diameters of the cooling channels and baffle tubes are determined by the mold designer according to their rule of0 Pa G 150000 pa ≤≤0 C oG 2 1.2 C o≤≤G 30 mm≤Figure 1. Finite element model of the product used for theoptimization.Figure 2. Configuration of cooling channels located alongthe offset profiles.Figure 3. Clusters consisting of 4 cooling channels with baffle tubes.DESIGN OPTIMIZATION OF AN INJECTION MOLD FOR MINIMIZING TEMPERATURE DEVIATION 275thumb (Rhee et al ., 2010). However, it has been examined in great detail among the mold designers. Table 1 shows the design variables with their ranges and initial values.The minimum values for the cooling channel distance,baffle distance and baffle depth were determined by the constraints of the machining requirement. The maximum values of cooling channel distance and baffle distance were determined by the empirical maximum obtained from the mold designers. The baffle distance was a discrete variable due to a restriction in the automated use of the CAE software. In this work, the baffle distances for optimization were 60, 90 and 120 mm.3.3. Objective FunctionA principal purpose of the mold cooling circuit optimization is to achieve uniform temperature distribution over the part. The uniform temperature distribution means that the temperature deviation caused by the cooling channels is minimized, as shown in Figure 4. The objective function in the optimization was the standard deviation of part temperature as shown in Equation (4). The part temperature was an arithmetic average of the upper and the lower surfaces of the mold halves. The mold surface temperature was calculated from the finite element of the part. min ,(4)whereσ is the standard deviation of the part temperature, E i is the temperature of i -th element, E w is the average temperature of the entire triangular elements, and N is the number of elements.4. OPTIMIZATION4.1. Parametric StudyIn order to examine the effects of the design variables on the objective function, pressure drop and temperature rise,parametric studies were carried out. A parametric study was performed by changing a variable in a certain range while keeping all other variables fixed. Figures 5-7 showthe results of parametric studies for the objective function,pressure drop temperature rise, respectively. In each figure,the x-axis indicates the levels of design variables. Every design variable was divided into 11 levels from its lower bound to its upper bound. -5 and 5 mean the lower and upper bounds, respectively.When examining the temperature deviation, the diameter of the cooling channels shows little influence to the objective function (see Figure 5.). This result was predictable because the cooling channel affects the parttemperature to a lesser degree than the baffle tubes in theautomotive bumper mold. The automotive bumper mold has a deep core so that the mold cooling depends upon the baffle tubes rather than the cooling channels. Another reason of the lack of influence can be that the flow state in the cooling channel remains turbulent in the range of the parametric study. The cooling channel usually has a smaller diameter than the baffle tube. When the flow in the baffle tube is kept in the turbulent state, the flow in the cooling channel will be in the turbulent state.The diameters of the baffle tubes show a tangible influence when it increases above a certain value.Increasing of the diameter changes the flow in the tube to a laminar flow state. This is the cause for the lower heat transfer coefficient when compared to the turbulent flow state. This is why the temperature deviation becomes larger when the baffle tube diameter increases.σE i E w –()2N --------------------i 1=N∑=Figure 4. Scheme of the temperature field by the cooling channels.Table 1. Lower and the upper bounds for design variables and the initial values for the optimization (unit: mm).DescriptionLower Initial Upper X 1Channel diameter 103040X 2Baffle diameter 103040X 3Channel distance 6090120X 4Baffle distance 6060120X 5Channel depth 306090X 6Baffle depth306090Figure 5. Parametric study result of temperature deviation (objective function).276J.-H. CHOI et al.Among all parameters, the baffle depth shows the largest influence on the objective function, as shown in Figure 5.As the baffle depth increases, the objective function increases. This means that the deeper location of the baffle tubes causes the temperature deviation to increase. Also, it confirms that the cooling of the automotive bumper mold depends upon the baffle tubes.The diameters of the cooling channels and the baffle tubes have the highest influence on the pressure drop in the cooling circuit, while the other variables show little influence (see Figure 6.). As the diameters increase, the pressure drop decreases after a certain value. This is also a predictable result as a larger diameter decreases the pressure drop.The influences of the temperature rise at the outlet are shown in Figure 7. The most influential parameters are the baffle diameter and the channel distance. The influence of the baffle diameter shows the highest values in the range from -1 to 3. In the case of the smaller baffle diameter, the reduced surface area for the heat transfer may cause a smaller temperature rise, while the larger baffle diameter may cause the lower heat transfer coefficient due to the lower flow rate.The increased channel distance means that each cooling channel takes up a larger area of the part surface with a larger amount of heat removal. This may give a physical explanation to why the increase of the temperature rise increases with channel distance. The fluctuations shown inFigure 7 are supposed to be numerical noise.4.2. Optimization ResultsThe largest increase in the temperature rise (Figure 7) is approximately 0.15o C. This value is much less than the constraint. The influence of the variables on the temperature rise is not tangible.The baffle distance was considered the discrete variable in this work; hence, it was difficult to apply a general optimization method. Because there were three values,optimizations were carried out 3 times with the 5 design parameters. The baffle distance was fixed in each optimization.Figures 8 and 9 show the temperature deviations as the channel diameter, x 1 and the channel distance, x 3 change by 0.1% using the perturbation method around their initial design values. From these results we recognized that the variations in the temperature deviations as x 1 and x 3 varied included numerical noise.Therefore, we chose PQRSM as the optimization method that could effectively optimize the response withnumerical noise. The PQRSM equipped in a commercialFigure 6. Parametric study result of the pressure drop.Figure 7. Parametric study result of the temperature rise.Figure 8. V ariation of the temperature deviation w.r.t. x 1observed by using 0.1% perturbation method.Figure 9. V ariation of the temperature deviation w.r.t. x 3observed by using 0.1% perturbation method.DESIGN OPTIMIZATION OF AN INJECTION MOLD FOR MINIMIZING TEMPERATURE DEVIATION277PIDO tool, PIAnO, approximates the objective function and constraints with quadratic functions in the trust region, and it sequentially moves and reduces the trust region until it finds the optimum solution.The results of the optimization using the PQRSM are shown in Table 2. Baseline represents the standard condition before applying the optimization. After the optimizations were carried out for the 3 cases of the baffle distance (x4), the lowest temperature deviation was obtained in the case of a baffle distance of 60 mm. Therefore we conclude that a baffle distance of 60 mm is our optimized result.At this optimized result, the temperature deviation was reduced by 19.2% compared to that of the baseline design while satisfying all other design requirements. Among the design variables, the channel diameter, x1, the baffle diameter, x2 and the channel distance, x3 remained close to their initial values while the channel depth, x5 moved toward the upper bound and the baffle depth, x6 toward the lower bound. Thus, we expect a better result if the bounds of the baffle distance, x4, channel depth, x5 and baffle depth, x6 can be relaxed.5. CONCLUSIONIn this study, we carried out the optimization of the cooling circuit for an automotive front bumper. The design objective was to minimize the temperature deviation while satisfying all constraints. There were three design constraints that included the pressure drop, temperature rise and aspect ratio, in addition to side constraints on six design variables.Among the six design variables, the baffle distance was the discrete design variable. Thus, we carried out optimizations for the three cases of baffle distances being 60, 90 and 120 mm. The lowest temperature deviation was obtained in the case of a baffle distance of 60 mm. In this case, the temperature deviation was reduced by 19.2% compared to the baseline design while satisfying all design requirements. It is believed that the design optimization approach of employing CAE and PIDO tools adopted in this study can be applied for the design of many industrial manufacturing processes.REFERENCESFRAMAX Inc (2009). PIAnO Tutorial.FRAMAX Inc(2009). PIAnO User’s Manual.Hong, K. ., Choi, D. H. and Kim, M. S. (2000). Progressive quadratic approximation method for effective constructing the second-order response surface models in the large scaled system design. The Kore an Socie ty of Me chanical Engine e rs(A)24, 12/12, 3040−3052.Koresawa, H. and Suzuki, H. (1999). Autonomous arrangement of cooling channels layout in injection molding. Proc. 1999 Annual Technological Conf. Society of Plastics Engineers, 1073−1077.Menges, G., Michaeli, W. and Mohren, P. (2001). How to MakeInjection Molds. 3rd Edn. Hanser Gardner Publications, Inc.. Ohio. 298−302.Rhee, B. O., Park, C. S., Chang H. K., Jung, H. W. and Lee, Y. J. (2010). Automatic generation of optimum cooling circuit for large injection molded parts. Int. J. Precision Eng. and Manufacturing, 11, 439−444.Table 2. Optimization results summary.Lower Baseline X4=60 X4=90 X4=120 Upperx1 10.00 30.00 29.67 28.39 30.00 40.00 x2 10.00 30.00 30.36 28.39 30.00 40.00 x3 60.00 90.00 89.37 90.29 88.13 120.00 x4 60.00 60.00 60.00 90.00 120.00 120.00 x5 30.00 60.00 87.63 88.81 90.00 90.00 x6 30.00 60.00 30.00 30.00 30.00 90.00 OBJ 6.62 5.35 5.60 5.46G1 016790 16904 16610 8758 50000G2 00.36 0.43 0.33 0.38 1.20G3 0.00 -0.69 0.00 0.00 0.00。
模具注射成型毕业论文中英文对照资料外文翻译文献
模具注射成型中英文对照资料外文翻译文献Injection MoldingThe basic concept of injection molding revolves around the ability of a thermoplastic material to be softened by heat and to harden when cooled .In most operations ,granular material (the plastic resin) is fed into one end of the cylinder (usually through a feeding device known as a hopper ),heated, and softened(plasticized or plasticated),forced out the other end of the cylinder,while it is still in the form of a melt,through a nozzle into a relatively cool mold held closed under pressure.Here,the melt cools and hardens until fully set-up.The mold is then opened,the piece ejected,and the sequence repeated.Thus,the significant elements of an injection molding machine become :1)the way in which the melt is plasticized (softened) and forced into the mold (called the injection unit);2)the system for opening the mold and closing it under pressure (called the clamping unit);3)the type of mold used;4)the machine controls.The part of an injection-molding machine,which converts a plastic material from a sold phase to homogeneous seni-liguid phase by raising its temperature .This unit maintains the material at a present temperature and force it through the injection unit nozzle into a mold .The plunger is a combination of the injection and plasticizing device in which a heating chamber is mounted between the plunger and mold. This chamber heats the plastic material by conduction .The plunger,on each storke; pushes unmelted plastic material into the chamber ,which in turn forces plastic melt at the front of the chamber out through the nozzleThe part of an injection molding machine in which the mold is mounted,and which provides the motion and force to open and close the mold and to hold the mold close with force during injection .This unit can also provide other features necessary for the effective functioning of the molding operation .Moving plate is the member of the clamping unit,which is moved toward a stationary member.the moving section of the mold is bolted to this moving plate .This member usually includes the ejector holes and moldmounting pattern of blot holes or “T”slots .Stationary plate is the fixed member of the clamping unit on which the stationary section of the mold is bolted .Thismember usually includes a mold-mounting pattern of boles or “T” slots.Tie rods are member of the clamping force actuating mechanism that serve as the tension member of the clamp whenit is holding the mold closed.They also serve as a gutde member for the movable plate .Ejector is a provision in the clamping unit that actuates a mechanism within the mold to eject the molded part(s) from the mold .The ejection actuating force may be applied hydraulically or pneumatically by a cylinder(s) attached to the moving plate ,or mechanically by the opening storke of the moving plate.Methods of melting and injecting the plastic differ from one machine to another and are constantly being improred .couventional machines use a cylinder and piston to do both jobs .This method simplifies machine construction but makes control of injection temperatures and pressures an inherently difficult problem .Other machines use a plastcating extruder to melt the plastic and piston to inject it while some hare been designed to use a screw for both jobs :Nowadays,sixty percent of the machines use a reciprocating screw,35% a plunger (concentrated in the smaller machine size),and 5%a screw pot. Many of the problems connected with in jection molding arises because the densities of polymers change so markedly withtemperature and pressure.Athigh temperatures,the density of a polymer is considerably cower than at room temperature,provided the pressure is the same.Therefore,if modls were filled at atmospheric pressure, “shrinkage”would make the molding deviate form the shape of the mold.To compensate for this poor effect, molds are filled at high pressure.The pressure compresses the polymer and allows more materials to flow into the mold,shrinkage is reduced and better quality moldings are produced.Cludes a mold-mounting pattern of bolt holes or “T”slots.Tie rods are members of the clamping force actuating machanism that serve as the tension members of clamp when it is holding the mold closed.Ejector is a provision in the claming unit that actuates a mechanism within the mold to eject themolded part(s) form the mold.The ejection actuating force may be applied hydraulically or pneumatically by a cylinder(s) attached to the moving plate,or mechanically by the opening stroke of the moving plate.The function of a mold is twofold :imparting the desired shape to the plasticized polymer and cooling the injection molded part.It is basically made up of two sets of components :the cavities and cores and the base in which the cavities and cores are mounted. The mold ,which contains one or morecavities,consists of two basic parts :(1) a stationary molds half one the side where the plastic is injected,(2)Amoving half on the closing or ejector side of the machine. The separation between the two mold halves is called the parting line.In some cases the cavity is partly in the stationary and partly in the moving section.The size and weight of the molded parts limit the number of cavities in the mold and also determine the machinery capacity required.The mold components and their functions are as following :(1)Mold Base-Hold cavity(cavities) in fixed ,correctposition relative to machine nozzle .(2)Guide Pins-Maintain Proper alignment of entry into moldintrior .(3)Sprue Bushing(sprue)-Provide means of entry into moldinterior .(4)Runners-Conrey molten plastic from sprue to cavities .(5)Gates-Control flow into cavities.(6)Cavity(female) and Force(male)-Contorl the size,shapeand surface of mold article.(7)Water Channels-Control the temperature of mold surfacesto chill plastic to rigid state.(8)Side (actuated by came,gears or hydrauliccylinders)-Form side holes,slots,undercuts and threaded sections.(9)Vent-Allow the escape of trapped air and gas.(10)Ejector Mechanism (pins,blades,stripper plate)-Ejectrigid molded article form cavity or force.(11)Ejector Return Pins-Return ejector pins to retractedposition as mold closes for next cycle.The distance between the outer cavities and the primary sprue must not be so long that the molten plastic loses too much heat in the runner to fill the outer cavities properly.The cavities should be so arranged around the primary sprue that each receives its full and equal share of the total pressure available,through its own runner system(or the so-called balanced runner system).The requires the shortest possible distance between cavities and primary sprue,equal runner and gate dimension,and uniform colling.注射成型注射成型的基本概念是使热塑性材料在受热时熔融,冷却时硬化,在大部分加工中,粒状材料(即塑料树脂)从料筒的一端(通常通过一个叫做“料斗”的进料装置)送进,受热并熔融(即塑化或增塑),然后当材料还是溶体时,通过一个喷嘴从料筒的另一端挤到一个相对较冷的压和封闭的模子里。
注射注塑模具外文翻译外文文献翻译、中英文翻译、外文翻译
外文资料翻译系部:专业:姓名:学号:外文出处:dvanced English literacy course(用外文写)附件:指导老师评语签名:年月日第一篇译文(中文)2.3注射模2.3.1注射模塑注塑主要用于热塑性制件的生产,它也是最古老的塑料成型方式之一。
目前,注塑占所有塑料树脂消费的30%。
典型的注塑产品主要有杯子器具、容器、机架、工具手柄、旋钮(球形捏手)、电器和通讯部件(如电话接收器),玩具和铅管制造装置。
聚合物熔体因其较高的分子质量而具有很高的粘性;它们不能像金属一样在重力流的作用下直接被倒入模具中,而是需要在高压的作用下强行注入模具中。
因此当一个金属铸件的机械性能主要由模壁热传递的速率决定,这决定了最终铸件的晶粒度和纤维取向,也决定了注塑时熔体注入时的高压产生强大的剪切力是物料中分子取向的主要决定力量。
由此所知,成品的机械性能主要受注射条件和在模具中的冷却条件影响。
注塑已经被应用于热塑性塑料和热固性塑料、泡沫部分,而且也已经被改良用于生产反应注塑过程,在此过程中,一个热固树脂系统的两个组成部分在模具中同时被注射填充,然后迅速聚合。
然而大多数注塑被用热塑性塑料上,接下来的讨论就集中在这样的模具上。
典型的注塑周期或流程包括五个阶段(见图2-1):(1)注射或模具填充;(2)填充或压紧;(3)定型;(4)冷却;(5)零件顶出。
图2-1 注塑流程塑料芯块(或粉末)被装入进料斗,穿过一条在注射料筒中通过旋转螺杆的作用下塑料芯块(或粉末)被向前推进的通道。
螺杆的旋转迫使这些芯块在高压下对抗使它们受热融化的料筒加热壁。
加热温度在265至500华氏度之间。
随着压力增强,旋转螺杆被推向后压直到积累了足够的塑料能够发射。
注射活塞迫使熔融塑料从料筒,通过喷嘴、浇口和流道系统,最后进入模具型腔。
在注塑过程中,模具型腔被完全充满。
当塑料接触冰冷的模具表面,便迅速固化形成表层。
由于型芯还处于熔融状态,塑料流经型芯来完成模具的填充。
外文原文(注塑模具设计文献翻译)
Effect of gate size on the melt filling behavior and residual stress of injection moldedpartsPengcheng Xie a ,Fengxia Guo a ,Zhiwei Jiao a ,Yumei Ding a ,Weimin Yang a ,b ,⇑a College of Mechanical and Electrical Engineering,Beijing University of Chemical Technology,Beijing 100029,ChinabState Key Laboratory of Organic–Inorganic Composites,Beijing University of Chemical Technology,Beijing 100029,Chinaa r t i c l e i n f o Article history:Received 8March 2013Accepted 28June 2013Available online 20July 2013Keywords:MoldingVisualization Flow behavior Residual stressa b s t r a c tThis paper studies the effects of gate size on the cavity filling pattern and residual stress of injection molded parts.A total of three rectangular gates with different sizes were used.Experiments were carried out by using a dynamic visualization system.A flow visualization mold was specially designed and made for this study.A high-speed video camera was used to record the mold filling phenomena of cavities with different gate size and different processing parameters.In addition,a Stress Viewer was used to charac-terize the residual stress of molded samples.It was found that the undersized gate has many adverse effects on the filling behavior and residual stress of molded parts.With a larger gate,the cavity will be filled faster and residual stress of parts may be smaller.The result of the study also indicates that nozzle temperature and injection rate can significantly affect the above two aspects.Ó2013Elsevier Ltd.All rights reserved.1.IntroductionGating system design is a key link in the process of injection mold design,because as a channel to connect the runner and the cavity,the gate plays a very important role.The design of gate not only affects the melt filling process,but also concerns the demolding process and separation of products and waste,thus affecting the production costs and benefits [1].Gate size as an essential aspect of gate design has very important influence on the quality of part.A gate with suitable dimension should be able to ensure the plastic filling with fast speed and good liquidity [2].And at the packing stage,gate must remain open long enough to inject additional material into the cavity for shrinkage-compensating.Generally,the gate size is established by experience.Cross-sec-tion of gate is typically smaller than that of the runner and parts,thus parts can be easily separated from the runner without leaving a visible scar on the part.In addition,when the material in the gate drops below the freeze temperature,there is the end of packing,therefore,the gate dimension controls the packing time.From these points of view,the overlarge gate is not desirable.In recent years,a large number of studies on gate design were carried out.But there are limited published works on studies relat-ing to design of gate size:Tor et al.[2]used five rectangular gateswith different ratio of width and depth to the impacts of gate size on the quality of powder injection molding.By performing the analysis of weight and density on the samples molded for each of the five gates,they evaluated the impact of different gate size.Shen et al.[3]analyzed the optimal gate design of thin-walled injection molding by using control volume finite element method.Xie and Ziegmann [4]investigated the effect of gate dimension on micro injection molded weld line strength with polypropylene (PP)and high-density polyethylene (HDPE)and found out some relation-ship between gate size and the quality of micro-molded part.This paper aims to intuitively display the influence of gate size on melt flow behavior in cavity,as well as the relationship between gate size and residual stress of parts.As moldings are used in wider areas,higher requirements for precision of products have been constantly put forward.How to suppress the generation of product defects (e.g.jet,weld lines,air bubbles,flash,crazing,etc.)and maximize the dimensional accuracy of products has been an important subject for researchers.Observing the flow behavior as an effective method could help people know the generation princi-ple of defects,and further to find out the causes and even the solu-tions [5].The emergence of visualization injection molding method applied an effective way for observing the phenomenon of melt flow in the mold.Injection molding visualization technology is a technology that the injection molding process can be directly ob-served.It is essentially adding a system that can real-time monitor-ing the filling process and reproducing the melt flow behavior in a conventional injection molding process,thus making the injection molding process from the traditional sense of ‘‘invisible’’becomes ‘‘visualization’’and ‘‘repeatable’’.Up to now,visualization method0261-3069/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.matdes.2013.06.071⇑Corresponding author at:College of Mechanical and Electrical Engineering,Beijing University of Chemical Technology,Beijing 100029,China.Tel./fax:+861064434734.E-mail address:yangwm@ (W.M Yang).has been widely used in multiple studies of injection.Yokoi has carried out a lot of research by this technique,for example,the study of molding process of two-color products,observation of flow front behavior duringfilling process with two-axis tracking system,analysis of thermoset phenolic resinflow behavior by Gate-Magnetization Method,and the study of meltfilling disci-pline of ultra-high speed injection molding[6–10],etc.In addition, by this method,Liu and Wu[11]compared the difference offilling process and molding parts between water-assisted and gas-as-sisted injection molding.Mehdi et al.[12]studied the bubbledynamics in foam injection molding.However,the visualization technology being applied to the gate size has not yet been found, in view of the successful application of it in above-mentioned areas,as well as the significant advantage it had shown,this study will use visualization techniques as one of the main means of research.Besides,defects in the products,such as warping and shrinkage, are detrimental to the quality and accuracy of the products[13]. Actually,an important factor causing these defects is residual stress.In general,the residual stress of injection molded products are divided into two Categories.One is the thermal residual stress, which is resulting during cooling period in the mold and after demolding[14].The other one is referred as residualflow stresses, which is due to the shear and normal stresses duringfilling and packing.Flow-induced stress is smaller than the former,but it could induce anisotropy of optical and some mechanical properties because of different molecular orientation in the directions of par-allel and perpendicular to theflow direction[15].Residual stress is not only the main cause of dimensional and shape inaccuracies of molded parts,but also responsible for environmental stress crack-ing[16,17].The dimension of gate influences the orientation of polymer molecule,fibers,and the mechanical and physical proper-ties of molding parts[18,19].Therefore,through comparing the residual stress of the products can provide the basis for the choice of gate size.Residual birefringence could be a valid measuring method for the polymer molecular orientation and residual stress [20],but it also can reflect a microscopic morphological structure of polymer products[21].Friedl[22]considered that the refractive index essentially contains all the information ofstatus characteristics of transparent injection products.In this paper,the visualization method was used toflow behavior in the case of different gate size.Throughthe differences offlow behavior with three gates underof injection parameters,the relationship between gatemeltfilling process will be drawn.And then,be used to measure the residual stresses in the molding experiment will be performed by Photo-elastic,whicheffect that the induced stresses inside a material willincoming light and form an interaction pattern.Thisbe related to the stress level and distribution inside the2.Experimental procedureThe injection experiment was conducted by the means injection molding.The emergence of visualizationing method applied an effective way for observing thenon of meltflow in the mold[5].The visual systemstudy including a injection molding machine,a visual mold,a high speed camera,a light and a data acquisition device.2.1.MaterialMaterial used in this study is an injection molding graded Polypropylene(PP,ST868M,from Chemical LCY,Taiwan),which is a random copolymer with ultra-high transparency,and its properties are listed in Table1.The recommended processing temperature ranges of190–270°C and the mold temperature is recommended between20and50°C.2.2.Part geometry and mold designThe mold cavity used in this paper is a tensile specimen with single gate.The geometries and dimensions of the tensile speci-mens were shown in Fig.1,which were designed and manufac-tured according to ISO527-2:2012[23].The gate of cavity is replaceable,three gates with different dimensions have been adopted in the experiment.Concretely,those gates have the same length(2mm)but different width and depth.According to the cross section size,they were respectively named as gate S(small), gate M(middle)and gate L(large),the actual sizes are shown in Ta-ble2.The middle gate size was selected based on experience val-ues,and then as the standard.The length and width of small gate and large gate were proportional changed and rounded.In order to facilitate the comparison,the small gate was made as small as possible,the cross-sectional edge length was as1/3times as the middle gate and into an integer of1Â1.Meanwhile,the large gate was expanded by the ratio of4/3times as the gate M,andfinal rounded to4Â3.Fig.2shows the photo of cavity plate used in the study,the cav-ity is processed on a removable patch,which could be tightly pressed on thefixed mold plate by positive pressure.When replac-ing the mold,people just need to loosen the screw then the embed-Table1General property of PP used in this study.Property Unit Globalene ST868M Density g/cm30.899MFI(meltflow rate)g/10cm18(230/2.16)Shrinkage% 1.3Tensile stress at yield MPa28Tensile strain at yield%12Heat deflection temperature°C88Table2Gate dimensions used in the experimental mold.Gate Small Middle Large Width(mm)134Depth(mm)1 2.53Length(mm)222Fig.1.Dimensions of tensile specimen.P.Xie et al./Materials and Design53(2014)366–372367the plastic molding processing is carried out in a closed flow chan-nel and cavity,the process of melt,mold filling,solidification and cooling are all invisible.Different to the conventional mold whose cavity is surrounded by metal,visual mold changed the cavity wall on the moving platen into a transparent quartz glass,and placed a mirror at a 45°angle in the other side of the glass.By the reflection of light,the phenomenon in the cavity can be observed from the outside.The rectangle in Fig.2shows the area that could be seen through the monitoring window.As shown in the figure,the length of monitoring window is smaller than the length of the article,so it to see the complete filling process through study.Fig.3shows the mold schematic.the melt filling process is nearly a transient the process to be seen by the naked eye This paper used a high-speed camera whose reach 17,500frames per second,and each moment of the filling process could be recorded clearly by it.The devices of visualization experiment are shown in Fig.4.2.3.Injection moldingAll specimens were prepared on an electric injection molding machine (GSK AE80).The maximum clamping force is 80tons,screw diameter is 32mm.The maximum injection velocity and volume can be provided is 300mm/s and 101cm 3.During the course of the experiment,corresponding to each set of experimen-tal parameters with different gates,more than 10shots were made before shooting to ensure that the process was stable.If no signifi-cation variation was observed during these runs,high-speed cam-era would be used to capture the melt filling process.Each set of parameters was shot five times,and the five specimens were col-lected for internal stress test.Table 3shows the experimental parameters and corresponding number.The packing pressure was always set to 80%of injection pressure,and packing time was 5s.The melting temperature was 240°C and mold tempera-ture was constantly at 35°C,original nozzle temperature was 190°C.3.Results discussion and analysis 3.1.Filling behaviorFig.5shows the flow behavior of melt front in the case of parameter (5)with gate S.In the initial stage of melt into the cav-ity,a small amount of material was straightly injected into the cav-ity and jetting occurred.And because of the decrease of temperature,the viscosity increased and the fluidity is reduced after the melt had flown through channel to the gate,a temporary filling hysteresis generated.Until a large enough pressure had been gradually built up,the low-temperature melt would be promoted into the cavity and moved forward,then the subsequent melt would flow smoothly through the gate and fill the cavity at a high-er speed.During the experiment process,it was found that sometimes the products obtained with gate S may be not fully formed,and increasing the rate and injection pressure can not completely solve the problem.The main reason is that the material in gate S had fro-zen before the cavity was filled completely.In order to obtain the full filled specimen,the method of improving the nozzle tempera-ture was tried,and the results showed that the nozzle temperature was a significant impact factor on the filling volume of small gate cavity.Fig.6is the filling volume of the parts shaped in the case of different injection pressure and nozzle temperature,it is obvious that the higher temperature of the nozzle,the greater the filling volume.The reason is that if the nozzle temperature is increased,the temperature of melt near the small gate will rise,thereby extending the gate solidification time,so that the melt filling quan-tity increases.Besides,increasing the injection pressure can also help to improve the filling volume.When using gate M and gate L,the melt fronts were smooth arcs,and there was no jetting or filling hysteresis occurred in the filling process.As shown in Fig.7,solid lines shows the regionFig.4.The equipments of visualization experiment.Fig.2.Photo of cavity plate.Table 3Experimental data and corresponding number.Inj.P (MPa)Inj.V (mm/s)408012010(1)(4)(7)30(2)(5)(8)50(3)(6)(9)Fig.3.Schematic of the visual mold.Design 53(2014)366–372can be directly observed,the wave front curve was derived directly from tracing the video capture,the contour shown in dashed line was inferred according to the flow pattern of the preceding para-graph.Through comparing between three schematic diagrams,it can be found that under the same processing parameters,a larger gate may cause a higher filling speed and there was hardly any short shot parts generated with gate M and gate L when the nozzle temperature was 190°C.The reason is that the volume flow rate of a large gate is generally higher than a small gate when the molding process is conducted in the same condition.As shown in Fig.8,through comparing the filling processes under different conditions,it can be concluded that the larger set of injection speed resulted in the faster filling rate.And there was no obvious relationship be-tween filling rate with injection pressure (Fig.9).On the whole,undersized gate like gate S will cause jetting and low filling speed.If molding process is conducted in condition of low injection rate or high injection pressure,the defect of shortshot will be able to generate.Therefore,for the filling behavior,undersized gate is disadvantageous.3.2.Residual stressThe residual stress in the specimens was examined by Stress Viewer R5.1(by Moldex3D,Fig.10),which is an instrument that could non-destructively and qualitatively observe the internal stress of transparent plastic parts.The instrument works by Brew-ster’s law of photo-elasticity.It uses the photo-elastic properties of plastic under stress to observe the variations of material birefrin-gence.When placing a transparent plastic sample between two polarized sheets and shining polarized light on it,the components of the light wave that are parallel and perpendicular to the direc-tion of the stress will propagate through the plastic with different speeds.Color fringes can be observed correspond to different speeds at that point,which in turn correspond to stress level,theFig.7.Filling process with three gates in the case of parameters (5).Fig.5.Filling process with gate S in the case of parameter (5).Fig.6.Specimens shaped by gate S with different nozzle temperature and injection pressure.principle is shown in Fig.11.From the color fringes patterns,the areas with higher density of color fringe lines higher stress inside can be learned.For a polymer material which has been subjected to stress and generated stress deformation,its refractive index of the light in the space will have a directional difference,in another words,the stress components of the plastic material in each directions are dif-ferent.As a result,the refractive index in these directions will also be different,and the difference will be proportional to the the for-mer.Therefore,by observing the light and dark fringes that were presented due to the different refractive index,the distribution and magnitude of residual stress can be known directly.With theoretic analysis and visualization techniques,Du et al.[24]once took rectangular plate cavity for the study,and observed the dynamic evolution process of residual stress during melt filling.They concluded that the residual stress near the point gate was sig-nificantly more than the fan gate.With the reduction of melt tem-perature or the increase of the holding pressure,the residual stress became larger.In this paper,the effects of various gate size andFig.10.Residual stress Viewer.Fig.11.Schematic diagram of birefringence.12.Residual stress distributions of specimens for three gates when injection rate was 30mm/s.9.Melt-flow-length of gate M with the injection speed of 30mms.(T-time,melt flow length)Melt-flow-length of gate M with the injection pressure of 40MPa.(T-time,flow length)parameters(including temperature,injection speed and injection pressure)on the residual stress were studied,and the discussion of the experimental results were as follows.As shown in Fig.12,when the injection rate was30mm/s and the nozzle temperature was190°C,the residual stress of speci-mens for three gates were significantly different.For ease of com-parison,the stress region had been divided into four parts according to the shape of the specimen.Stress of specimens shaped with gate S distributed much wider than specimens of the other two gates,the stress concentrations in the region of part2and part 3were particularly pared to gate S,residual stress of specimens shaped with gate M and L was much less than the for-mer.Difference between gate M and gate L was not obvious,but residual orientation,namely frozen in orientation[25,26].The chains with frozen orientation always have a development trend from high energy state to lower energy state,it means they may tend to curl,wound,or recrystallization,this will lead to inconsis-tent alignment direction and further generate internal stresses[26]. Therefore,when the meltflow rate is slower,the cooling rate will be faster,then the frozen in orientation will be more serious,thus the residual stress of products will be larger.That is why articles of gate S have the maximum residual stress and L has the minimum.Another set of contrasting results further demonstrate the influ-ence of temperature on the residual stress.As shown in Fig.14,in the case of injection rate of10mm/s,injection pressure of 120MPa,different nozzle temperature caused different residualFig.14.Residual stress distributions of specimens for gate S under different nozzle temperature.Fig.15.Residual stress distributions of specimens molded by gate M.Fig.13.Fig.13.Sketch of chains of a polymeric in different state[27]P.Xie et al./Materials and Design53(2014)366–372371the wall and in the center is larger than when the temperature was low,the cooling rate is uneven,made the difference of segment ori-entation became greater and thus the phenomenon occurred.In general,the residual stress will decline as the temperature rising, which is consistent with the conclusion of Du[24].In addition to the effect of gate size on residual stress,which also can be seen from Fig.12is that injection pressure has no sig-nificantly influence on the residual stress in this experiment.Fig.15shows the residual stress distribution of specimens molded by gate M.It can be found that the injection rate has a great influence on the residual stress.When the rate was10mm/ s,the residual stress distribution was the biggest and the difference with each other mainly lied in part1.The smallest stress was gen-erated in the case of50mm/s.This result suggests that a large speed is helpful to reducing the residual stress.Reason is that most of the polymer molecular chains are arranged along theflow direc-tion in thefilling process.Due to the faster injection rate resulted in the higher shear rate of the melt,it will lead to the higher orien-tation degree of the segment.Therefore,the preference consistency of products segment will be higher,while theflow residual stress will be small.From another point of view,due to the high injection rate,the temperature of melt in the cavity is relatively uniformly and high,according to the previous conclusions,it can be known that the thermal residual stress will also be small.Therefore,the total residual stress will be lower when the injection rate is higher.4.ConclusionsAccording to the results of injection molding visualization experiments and observations on residual stress,the following conclusions could be drawn.(1)Gate size is an important factor affecting thefilling behavior.The undersized gate will cause jetting and lowfilling speed, and is likely to produce short shot products.If the gate is appropriately enlarged,thefilling speed,flow stability and integrity of products will all be improved.Moreover,these effects are coupled with processing conditions,altering the injection speed and nozzle temperature will cause the change offilling behavior.(2)Gate can significantly impact the magnitude and distribu-tion of residual stress:A larger gate may generate smaller stress.Besides,the effect of injection speed and temperature on residual stress should not be ignored.The residual stress will be likely to reduce when the melt isfilling in a higher speed or a higher nozzle temperature.Through comparing between these three gates,it can be identi-fied in this paper that the undersized gate has many adverse effects on thefilling process and the residual stress.However,based on the traditional experience,the gate is not the larger the better.Fur-ther study is needed to be carried out in this aspect. AcknowledgementsThe authors are supported by the Laboratory of Advanced Poly-mer Processing.We gratefully acknowledge CoreTech System Co.,Ltd.(Moldex3D)and GSK CNC Equipment Co.,Ltd.for their gener-ous supply of the devices.Funding was provided by the National Natural Science Foundation of China(Grant Nos.51203009and 21174015).References[1]Pye RGW.Injection Mould Design.Harlow(Longman Scientific&Technical);1989.p.358.[2]Tor SB,Loh NH,Khor KA,Yoshida H.The effects of gate size in powder injectionmolding.Mater Manuf Processes1997;12(4):629–40.[3]Shen YK,Wu CW,Yuc YF,Chungc HW.Analysis for optimal gate design of thin-walled injection molding.Int Commun Heat Mass Trans2008;35(6):728–34.[4]Xie L,Ziegmann G.Effect of gate dimension on micro injection molded weldline strength with polypropylene(PP)and high-density polyethylene(HDPE).Int J Adv Manuf Technol2010;48(1–4):71–81.[5]Xie PC,Du B,Yan ZY,Ding YM,Yang WM.Visual experiment study on theinfluence of mold structure design on injection molding product’s defects.Adv Mater Res2010;87–88:31–5.[6]Yokoi H.Recent development of visualization analysis techniques in injectionmolding.Denso Tech Rev2006;11(2):3–13.[7]Yokoi H,Masuda N,Mitsuhata H.Visualization analysis offlow front behaviorduringfilling process of injection mold cavity by two-axis tracking system.J Mater Process Technol2002;130–131:328–33.[8]Ohta T,Yokoi H.Visual analysis of cavityfilling and packing process ininjection molding of thermoset phenolic resin by the gate-magnetization method.Polym Eng Sci2001;41(5):806–19.[9]Yokoi H.Visualization and measurement technologies for ultra-high-speedinjection molding phenomena.Prod Res2007;59:483–91.[10]Yoshimura Y,Endo M,Yokoi H.Visualization analysis of meltfilling behaviorfrom submarine-gate in ultra-high-speed injection molding.Prod Res 2009;61:985–8.[11]Liu SJ,Wu YC.Dynamic visualization of cavity-filling process influid-assistedinjection molding-gas versus water.Polym Test2007;26(2):232–42.[12]Mehdi M,Amir HB,Mohammad Rezavand SA,Amir P.Visualization of bubbledynamics in foam injection molding.J Appl Polym Sci2010;116(6):3346–55.[13]Demirer A,Soydan Y,Kapti AO.An experimental investigation of the effects ofhot runner system on injection moulding process in comparison with conventional runner system.Mater Des2007;28:1467–76.[14]Wang TH,Young WB.Study on residual stresses of thin-walled injectionmolding.Euro Polym J2005;41:2511–7.[15]Zoetelief WF,Douven LFA,Ingen Housz AJ.Residual thermal stresses ininjection molded products.Polym Eng Sci1996;36(14):1886–96.[16]Kamal MR,Lai-Fook RA,Hernandez-Aguilar JR.Residual thermal stresses ininjection moldings of thermoplastics:a theoretical and experimental study.Polym Eng Sci2002;42(5):1098–114.[17]Wimberger-Friedl R,de Bruin JG,Schoo HFM.Residual birefringence inmodified polycarbonates.Polym Eng Sci2003;43(1):62–70.[18]Fiske T,Gokturk HS,Yazici R,Kalyon DM.Effects offlow induced orientation offerromagnetic particles on relative magnetic permeability of injection molded composites.Polym Eng Sci1997;37(5):826.[19]Yamada K,Tomari K,Ishiaku US,Hamada H.Fracture toughness evaluation ofadjacentflow weld line in polystyrene by the SENB method.Polym Eng Sci 2005;45(8):1059–66.[20]Tumbull A,Maxwell AS,Pillai S.Residual stress in polymers evaluation ofmeasurement techniques.J Mater Sci1999;34(3):451–9.[21]Neves NM,Pouzada AS.The use of birefringence for predicting the stiffness ofinjection molded polycarbonate discs.Polym Eng Sci1998;38(10):1770–7. [22]Wimberger-Friedl R.The assessment of orientation,stress and densitydistributions in injection-molded amorphous polymers by optical techniques.Prog Polym Sci1995;20(3):369–99.[23]ISO527-2.Plastics—determination of tensile properties—Part2:Testconditions for moulding and extrusion plastics;2012.[24]Du B.Dynamic visualization experimental study of internal stress on theoptical products.Beijing University of Chemical Technology;2011.[25]Jansen KMB,Flaman AAM.The influence of surface heating on thebirefringence distribution in injection molded parts.Polym Eng Sci 1994;34(11):898–904.[26]Xu QJ,Yu SW.Calculation of residual stress in injection molded productionmolded products for polymer materials.Chinese J Theor Appl Mech 1998;30:157–67.[27]ten Grotenhuis SM,Piazolo S,Pakula T,Passchier CW,Bons PD.Are polymerssuitable rock analogs?Tectonophysics2002;350(1):35–47.372P.Xie et al./Materials and Design53(2014)366–372。
注塑模具中英文对照外文翻译文献
中英文对照资料外文翻译Integrated simulation of the injection molding process withstereolithography moldsAbstract Functional parts are needed for design verification testing, field trials, customer evaluation, and production planning. By eliminating multiple steps, the creation of the injection mold directly by a rapid prototyping (RP) process holds the best promise of reducing the time and cost needed to mold low-volume quantities of parts. The potential of this integration of injection molding with RP has been demonstrated many times. What is missing is the fundamental understanding of how the modifications to the mold material and RP manufacturing process impact both the mold design and the injection molding process. In addition, numerical simulation techniques have now become helpful tools of mold designers and process engineers for traditional injection molding. But all current simulation packages for conventional injection molding are no longer applicable to this new type of injection molds, mainly because the property of the mold material changes greatly. In this paper, an integrated approach to accomplish a numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. Comparisons with experimental results are employed for verification, which show that the present scheme is well suited to handle RP fabricated stereolithography (SL) molds.Keywords Injection molding Numerical simulation Rapid prototyping1 IntroductionIn injection molding, the polymer melt at high temperature is injected into the mold under high pressure [1]. Thus, the mold material needs to have thermal and mechanical properties capable of withstanding the temperatures and pressures of the molding cycle. The focus of many studies has been to create theinjection mold directly by a rapid prototyping (RP) process. By eliminating multiple steps, this method of tooling holds the best promise of reducing the time and cost needed to createlow-volume quantities of parts in a production material. The potential of integrating injection molding with RP technologies has been demonstrated many times. The properties of RP molds are very different from those of traditional metal molds. The key differences are the properties of thermal conductivity and elastic modulus (rigidity). For example, the polymers used in RP-fabricated stereolithography (SL) molds have a thermal conductivity that is less than one thousandth that of an aluminum tool. In using RP technologies to create molds, the entire mold design and injection-molding process parameters need to be modified and optimized from traditional methodologies due to the completely different tool material. However, there is still not a fundamental understanding of how the modifications to the mold tooling method and material impact both the mold design and the injection molding process parameters. One cannot obtain reasonable results by simply changing a few material properties in current models. Also, using traditional approaches when making actual parts may be generating sub-optimal results. So there is a dire need to study the interaction between the rapid tooling (RT) process and material and injection molding, so as to establish the mold design criteria and techniques for an RT-oriented injection molding process.In addition, computer simulation is an effective approach for predicting the quality of molded parts. Commercially available simulation packages of the traditional injection molding process have now become routine tools of the mold designer and process engineer [2]. Unfortunately, current simulation programs for conventional injection molding are no longer applicable to RP molds, because of the dramatically dissimilar tool material. For instance, in using the existing simulation software with aluminum and SL molds and comparing with experimental results, though the simulation values of part distortion are reasonable for the aluminum mold, results are unacceptable, with the error exceeding 50%. The distortion during injection molding is due to shrinkage and warpage of the plastic part, as well as the mold. For ordinarily molds, the main factor is the shrinkage and warpage of the plastic part, which is modeled accurately in current simulations. But for RP molds, the distortion of the mold has potentially more influence, which have been neglected in current models. For instance, [3] used a simple three-step simulation process to consider the mold distortion, which had too much deviation.In this paper, based on the above analysis, a new simulation system for RP molds is developed. The proposed system focuses on predicting part distortion, which is dominating defect in RP-molded parts. The developed simulation can be applied as an evaluation tool for RP mold design and process opti mization. Our simulation system is verified by an experimental example.Although many materials are available for use in RP technologies, we concentrate on usingstereolithography (SL), the original RP technology, to create polymer molds. The SL process uses photopolymer and laser energy to build a part layer by layer. Using SL takes advantage of both the commercial dominance of SL in the RP industry and the subsequent expertise base that has been developed for creating accurate, high-quality parts. Until recently, SL was primarily used to create physical models for visual inspection and form-fit studies with very limited func-tional applications. However, the newer generation stereolithographic photopolymers have improved dimensional, mechanical and thermal properties making it possible to use them for actual functional molds.2 Integrated simulation of the molding process2.1 MethodologyIn order to simulate the use of an SL mold in the injection molding process, an iterative method is proposed. Different software modules have been developed and used to accomplish this task. The main assumption is that temperature and load boundary conditions cause significant distortions in the SL mold. The simulation steps are as follows:1The part geo metry is modeled as a solid model, which is translated to a file readable by the flow analysis package.2Simulate the mold-filling process of the melt into a pho topolymer mold, which will output the resulting temperature and pressure profiles.3Structural analysis is then performed on the photopolymer mold model using the thermal and load boundary conditions obtained from the previous step, which calculates the distortion that the mold undergo during the injection process.4If the distortion of the mold converges, move to the next step. Otherwise, the distorted mold cavity is then modeled (changes in the dimensions of the cavity after distortion), and returns to the second step to simulate the melt injection into the distorted mold.5The shrinkage and warpage simulation of the injection molded part is then applied, which calculates the final distor tions of the molded part.In above simulation flow, there are three basic simulation mod ules.2. 2 Filling simulation of the melt2.2.1 Mathematical modelingIn order to simulate the use of an SL mold in the injection molding process, an iterativemethod is proposed. Different software modules have been developed and used to accomplish this task. The main assumption is that temperature and load boundary conditions cause significant distortions in the SL mold. The simulation steps are as follows:1. The part geometry is modeled as a solid model, which is translated to a file readable by the flow analysis package.2. Simulate the mold-filling process of the melt into a photopolymer mold, which will output the resulting temperature and pressure profiles.3. Structural analysis is then performed on the photopolymer mold model using the thermal and load boundary conditions obtained from the previous step, which calculates the distortion that the mold undergo during the injection process.4. If the distortion of the mold converges, move to the next step. Otherwise, the distorted mold cavity is then modeled (changes in the dimensions of the cavity after distortion), and returns to the second step to simulate the melt injection into the distorted mold.5. The shrinkage and warpage simulation of the injection molded part is then applied, which calculates the final distortions of the molded part.In above simulation flow, there are three basic simulation modules.2.2 Filling simulation of the melt2.2.1 Mathematical modelingComputer simulation techniques have had success in predicting filling behavior in extremely complicated geometries. However, most of the current numerical implementation is based on a hybrid finite-element/finite-difference solution with the middleplane model. The application process of simulation packages based on this model is illustrated in Fig. 2-1. However, unlike the surface/solid model in mold-design CAD systems, the so-called middle-plane (as shown in Fig. 2-1b) is an imaginary arbitrary planar geometry at the middle of the cavity in the gap-wise direction, which should bring about great inconvenience in applications. For example, surface models are commonly used in current RP systems (generally STL file format), so secondary modeling is unavoidable when using simulation packages because the models in the RP and simulation systems are different. Considering these defects, the surface model of the cavity is introduced as datum planes in the simulation, instead of the middle-plane.According to the previous investigations [4–6], fillinggoverning equations for the flow and temperature field can be written as:where x, y are the planar coordinates in the middle-plane, and z is the gap-wise coordinate; u, v,w are the velocity components in the x, y, z directions; u, v are the average whole-gap thicknesses; and η, ρ,CP (T), K(T) represent viscosity, density, specific heat and thermal conductivity of polymer melt, respectively.Fig.2-1 a–d. Schematic procedure of the simulation with middle-plane model. a The 3-D surface model b The middle-plane model c The meshed middle-plane model d The display of the simulation result In addition, boundary conditions in the gap-wise direction can be defined as:where TW is the constant wall temperature (shown in Fig. 2a).Combining Eqs. 1–4 with Eqs. 5–6, it follows that the distributions of the u, v, T, P at z coordinates should be symmetrical, with the mirror axis being z = 0, and consequently the u, v averaged in half-gap thickness is equal to that averaged in wholegap thickness. Based on this characteristic, we can divide the whole cavity into two equal parts in the gap-wise direction, as described by Part I and Part II in Fig. 2b. At the same time, triangular finite elements are generated in the surface(s) of the cavity (at z = 0 in Fig. 2b), instead of the middle-plane (at z = 0 in Fig. 2a). Accordingly, finite-difference increments in the gapwise direction are employed only in the inside of the surface(s) (wall to middle/center-line), which, in Fig. 2b, means from z = 0 to z = b. This is single-sided instead of two-sided with respect to the middle-plane (i.e. from the middle-line to two walls). In addition, the coordinate system is changed from Fig. 2a to Fig. 2b to alter the finite-element/finite-difference scheme, as shown in Fig. 2b. With the above adjustment, governing equations are still Eqs. 1–4. However, the original boundary conditions inthe gapwise direction are rewritten as:Meanwhile, additional boundary conditions must be employed at z = b in order to keep the flows at the juncture of the two parts at the same section coordinate [7]:where subscripts I, II represent the parameters of Part I and Part II, respectively, and Cm-I and Cm-II indicate the moving free melt-fronts of the surfaces of the divided two parts in the filling stage.It should be noted that, unlike conditions Eqs. 7 and 8, ensuring conditions Eqs. 9 and 10 are upheld in numerical implementations becomes more difficult due to the following reasons:1. The surfaces at the same section have been meshed respectively, which leads to a distinctive pattern of finite elements at the same section. Thus, an interpolation operation should be employed for u, v, T, P during the comparison between the two parts at the juncture.2. Because the two parts have respective flow fields with respect to the nodes at point A and point C (as shown in Fig. 2b) at the same section, it is possible to have either both filled or one filled (and one empty). These two cases should be handled separately, averaging the operation for the former, whereas assigning operation for the latter.3. It follows that a small difference between the melt-fronts is permissible. That allowance can be implemented by time allowance control or preferable location allowance control of the melt-front nodes.4. The boundaries of the flow field expand by each melt-front advancement, so it is necessary to check the condition Eq. 10 after each change in the melt-front.5. In view of above-mentioned analysis, the physical parameters at the nodes of the same section should be compared and adjusted, so the information describing finite elements of the same section should be prepared before simulation, that is, the matching operation among the elements should be preformed.Fig. 2a,b. Illustrative of boundary conditions in the gap-wise direction a of the middle-plane model b of thesurface model2.2.2 Numerical implementationPressure field. In modeling viscosity η, which is a function of shear rate, temperature and pressure of melt, the shear-thinning behavior can be well represented by a cross-type model such as:where n corresponds to the power-law index, and τ∗ characterizes the shear stress level of the transition region between the Newtonian and power-law asymptotic limits. In terms of an Arrhenius-type temperature sensitivity and exponential pressure dependence, η0(T, P) can be represented with reasonable accuracy as follows:Equations 11 and 12 constitute a five-constant (n, τ∗, B, Tb, β) representation for viscosity. The shear rate for viscosity calculation is obtained by:Based on the above, we can infer the following filling pressure equation from the governing Eqs. 1–4:where S is calculated by S = b0/(b−z)2η d z. Applying the Galerkin method, the pressure finite-element equation is deduced as:where l_ traverses all elements, including node N, and where I and j represent the local node number in element l_ corresponding to the node number N and N_ in the whole, respectively. The D(l_) ij is calculated as follows:where A(l_) represents triangular finite elements, and L(l_) i is the pressure trial function in finite elements.Temperature field. To determine the temperature profile across the gap, each triangular finite element at the surface is further divided into NZ layers for the finite-difference grid.The left item of the energy equation (Eq. 4) can be expressed as:where TN, j,t represents the temperature of the j layer of node N at time t.The heat conduction item is calculated by:where l traverses all elements, including node N, and i and j represent the local node number in element l corresponding to the node number N and N_ in the whole, respectively.The heat convection item is calculated by:For viscous heat, it follows that:Substituting Eqs. 17–20 into the energy equation (Eq. 4), the temperature equation becomes:2.3 Structural analysis of the moldThe purpose of structural analysis is to predict the deformation occurring in the photopolymer mold due to the thermal and mechanical loads of the filling process. This model is based on a three-dimensional thermoelastic boundary element method (BEM). The BEM is ideally suited for this application because only the deformation of the mold surfaces is of interest. Moreover, the BEM has an advantage over other techniques in that computing effort is not wasted on calculating deformation within the mold.The stresses resulting from the process loads are well within the elastic range of the mold material. Therefore, the mold deformation model is based on a thermoelastic formulation. The thermal and mechanical properties of the mold are assumed to be isotropic and temperature independent.Although the process is cyclic, time-averaged values of temperature and heat flux are used for calculating the mold deformation. Typically, transient temperature variations within a mold have been restricted to regions local to the cavity surface and the nozzle tip [8]. The transients decay sharply with distance from the cavity surface and generally little variation is observed beyond distances as small as 2.5 mm. This suggests that the contribution from the transients to the deformation at the mold block interface is small, and therefore it is reasonable to neglect the transient effects. The steady state temperature field satisfies Laplace’s equation 2T = 0 and the time-averaged boundary conditions. The boundary conditions on the mold surfaces are described in detail by Tang et al. [9]. As for the mechanical boundary conditions, the cavity surface is subjected to the melt pressure, the surfaces of the mold connected to the worktable are fixed in space, and other external surfaces are assumed to be stress free.The derivation of the thermoelastic boundary integral formulation is well known [10]. It is given by:where uk, pk and T are the displacement, traction and temperature,α, ν represent the thermal expansion coefficient and Poisson’s ratio of the material, and r = |y−x|. clk(x) is the surfacecoefficient which depends on the local geometry at x, the orientation of the coordinate frame and Poisson’s ratio for the domain [11]. The fundamental displacement ˜ulk at a point y in the xk direction, in a three-dimensional infinite isotropic elastic domain, results from a unit load concentrated at a point x acting in the xl direction and is of the form:where δlk is the Kronecker delta function and μ is the shear modulus of the mold material.The fundamental traction ˜plk , measured at the point y on a surface with unit normal n, is:Discretizing the surface of the mold into a total of N elements transforms Eq. 22 to:where Γn refers to the n th surface element on the domain.Substituting the appropriate linear shape functions into Eq. 25, the linear boundary element formulation for the mold deformation model is obtained. The equation is applied at each node on the discretized mold surface, thus giving a system of 3N linear equations, where N is the total number of nodes. Each node has eight associated quantities: three components of displacement, three components of traction, a temperature and a heat flux. The steady state thermal model supplies temperature and flux values as known quantities for each node, and of the remaining six quantities, three must be specified. Moreover, the displacement values specified at a certain number of nodes must eliminate the possibility of a rigid-body motion or rigid-body rotation to ensure a non-singular system of equations. The resulting system of equations is assembled into a integrated matrix, which is solved with an iterative solver.2.4 Shrinkage and warpage simulation of the molded partInternal stresses in injection-molded components are the principal cause of shrinkage and warpage. These residual stresses are mainly frozen-in thermal stresses due to inhomogeneous cooling, when surface layers stiffen sooner than the core region, as in free quenching. Based onthe assumption of the linear thermo-elastic and linear thermo-viscoelastic compressible behavior of the polymeric materials, shrinkage and warpage are obtained implicitly using displacement formulations, and the governing equations can be solved numerically using a finite element method.With the basic assumptions of injection molding [12], the components of stress and strain are given by:The deviatoric components of stress and strain, respectively, are given byUsing a similar approach developed by Lee and Rogers [13] for predicting the residual stresses in the tempering of glass, an integral form of the viscoelastic constitutive relationships is used, and the in-plane stresses can be related to the strains by the following equation:Where G1 is the relaxation shear modulus of the material. The dilatational stresses can be related to the strain as follows:Where K is the relaxation bulk modulus of the material, and the definition of α and Θ is:If α(t) = α0, applying Eq. 27 to Eq. 29 results in:Similarly, applying Eq. 31 to Eq. 28 and eliminating strain εxx(z, t) results in:Employing a Laplace transform to Eq. 32, the auxiliary modulus R(ξ) is given by:Using the above constitutive equation (Eq. 33) and simplified forms of the stresses and strains in the mold, the formulation of the residual stress of the injection molded part during the cooling stage is obtain by:Equation 34 can be solved through the application of trapezoidal quadrature. Due to the rapid initial change in the material time, a quasi-numerical procedure is employed for evaluating the integral item. The auxiliary modulus is evaluated numerically by the trapezoidal rule.For warpage analysis, nodal displacements and curvatures for shell elements are expressed as:where [k] is the element stiffness matrix, [Be] is the derivative operator matrix, {d} is the displacements, and {re} is the element load vector which can be evaluated by:The use of a full three-dimensional FEM analysis can achieve accurate warpage results, however, it is cumbersome when the shape of the part is very complicated. In this paper, a twodimensional FEM method, based on shell theory, was used because most injection-molded parts have a sheet-like geometry in which the thickness is much smaller than the other dimensions of the part. Therefore, the part can be regarded as an assembly of flat elements to predict warpage. Each three-node shell element is a combination of a constant strain triangular element (CST) and a discrete Kirchhoff triangular element (DKT), as shown in Fig. 3. Thus, the warpage can be separated into plane-stretching deformation of the CST and plate-bending deformation of the DKT, and correspondingly, the element stiffness matrix to describe warpage can also be divided into the stretching-stiffness matrix and bending-stiffness matrix.Fig. 3a–c. Deformation decomposition of shell element in the local coordinate system. a In-plane stretchingelement b Plate-bending element c Shell element3 Experimental validationTo assess the usefulness of the proposed model and developed program, verification is important. The distortions obtained from the simulation model are compared to the ones from SL injection molding experiments whose data is presented in the literature [8]. A common injection molded part with the dimensions of 36×36×6 mm is considered in the experiment, as shown in Fig. 4. The thickness dimensions of the thin walls and rib are both 1.5 mm; and polypropylene was used as the injection material. The injection machine was a production level ARGURY Hydronica 320-210-750 with the following process parameters: a melt temperature of 250 ◦C; an ambient temperature of 30 ◦C; an injection pressure of 13.79 MPa; an injection time of 3 s; and a cooling time of 48 s. The SL material used, Dupont SOMOSTM 6110 resin, has the ability to resist temperatures of up to 300 ◦C temperatures. As mentioned above, thermal conductivity of the mold is a major factor that differentiates between an SL and a traditional mold. Poor heat transfer in the mold would produce a non-uniform temperature distribution, thus causing warpage that distorts the completed parts. For an SL mold, a longer cycle time would be expected. The method of using a thin shell SL mold backed with a higher thermal conductivity metal (aluminum) was selected to increase thermal conductivity of the SL mold.Fig. 4. Experimental cavity modelFig. 5. A comparison of the distortion variation in the X direction for different thermal conductivity; where “Experimental”, “present”, “three-step”, and “conventional” mean the results of the experimental, the presented simulation, the three-step simulation process and the conventional injection molding simulation, respectively.Fig. 6. Comparison of the distortion variation in the Y direction for different thermal conductivitiesFig. 7. Comparison of the distortion variation in the Z direction for different thermal conductivitiesFig. 8. Comparison of the twist variation for different thermal conductivities For this part, distortion includes the displacements in three directions and the twist (the difference in angle between two initially parallel edges). The validation results are shown in Fig.5 to Fig. 8. These figures also include the distortion values predicted by conventional injection molding simulation and the three-step model reported in [3].4 ConclusionsIn this paper, an integrated model to accomplish the numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. For verification, an experiment is also carried out with an RPfabricated SL mold.It is seen that a conventional simulation using current injection molding software breaks down for a photopolymer mold. It is assumed that this is due to the distortion in the mold caused by the temperature and load conditions of injection. The three-step approach also has much deviation. The developed model gives results closer to experimental.Improvement in thermal conductivity of the photopolymer significantly increases part quality. Since the effect of temperature seems to be more dominant than that of pressure (load), an improvement in the thermal conductivity of the photopolymer can improve the part quality significantly.Rapid Prototyping (RP) is a technology makes it possible to manufacture prototypes quickly and inexpensively, regardless of their complexity. Rap id Tooling (RT) is the next step in RP’s steady progress and much work is being done to obtain more accurate tools to define the parameters of the process. Existing simulation tools can not provide the researcher with a useful means of studying relative changes. An integrated model, such as the one presented in this paper, is necessary to obtain accurate predictions of the actual quality of final parts. In the future, we expect to see this work expanded to develop simulations program for injection into RP molds manufactured by other RT processes.References1. Wang KK (1980) System approach to injection molding process. Polym-Plast Technol Eng 14(1):75–93.2. Shelesh-Nezhad K, Siores E (1997) Intelligent system for plastic injection molding process design. J Mater Process Technol 63(1–3):458–462.3. Aluru R, Keefe M, Advani S (2001) Simulation of injection molding into rapid-prototyped molds. Rapid Prototyping J 7(1):42–51.4. Shen SF (1984) Simulation of polymeric flows in the injection molding process. Int J Numer Methods Fluids 4(2):171–184.5. Agassant JF, Alles H, Philipon S, Vincent M (1988) Experimental and theoretical study of the injection molding of thermoplastic materials. Polym Eng Sci 28(7):460–468.6. Chiang HH, Hieber CA, Wang KK (1991) A unified simulation of the filling and post-filling stages in injection molding. Part I: formulation. Polym Eng Sci 31(2):116–124.7. Zhou H, Li D (2001) A numerical simulation of the filling stage in injection molding based on a surface model. Adv Polym Technol 20(2):125–131.8. Himasekhar K, Lottey J, Wang KK (1992) CAE of mold cooling in injection molding using a three-dimensional numerical simulation. J EngInd Trans ASME 114(2):213–221.9. Tang LQ, Pochiraju K, Chassapis C, Manoochehri S (1998) Computeraided optimization approach for the design of injection mold cooling systems. J Mech Des, Trans ASME 120(2):165–174.10. Rizzo FJ, Shippy DJ (1977) An advanced boundary integral equation method for three-dimensional thermoelasticity. Int J Numer Methods Eng 11:1753–1768.11. Hartmann F (1980) Computing the C-matrix in non-smooth boundary points. In: New developments in boundary element methods, CML Publications, Southampton, pp 367–379.12. Chen X, Lama YC, Li DQ (2000) Analysis of thermal residual stress in plastic injection molding. J Mater Process Technol 101(1):275–280.13. Lee EH, Rogers TG (1960) Solution of viscoelastic stress analysis problems using measured creep or relaxation function. J Appl Mech 30(1):127–134.14. Li Y (1997) Studies in direct tooling using stereolithography. Dissertation, University of Delaware, Newark, DE..。
注塑成型的实验研究外文文献翻译、注射模注塑模塑料模具中英文翻译、外文翻译
附录附录1An experimental study of the water-assisted injection molding ofglass fiber filled poly-butylene-terephthalate(PBT) compositesAbstract:The purpose of this report was to experimentally study the water-assisted injection molding process of poly-butylene-terephthalate(PBT) composites. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system,which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator,and a control circuit. The materials included virgin PBT and a 15% glass fiber filled PBT composite, and a plate cavity with a rib across center was used. Various processing variables were examined in terms of their influence on the length of water penetration in molded parts, and mechanical property tests were performed on these parts. X-ray diffraction (XRD) was also used to identify the material and structural parameters. Finally, a comparison was made between water-assisted and gas-assisted injection molded parts. It was found that the melt fill pressure, melt temperature, and short shot size were the dominant parameters affecting water penetration behavior.Material at the mold-side exhibited a higher degree of crystallinity than that at the water-side. Parts molded by gas also showed a higher degree of crystallinity than those molded by water. Furthermore, the glass fibers near the surface of molded parts were found to be oriented mostly in the flow direction, but oriented substantially more perpendicular to the flow direction with increasing distance from the skin surface.Keywords: Water assisted injection molding; Glass fiber reinforced poly-butylene-terephthalate (PBT) composites; Processing parameters; B. Mechanical properties; Crystallinity; A. Polymer matrix composites;1. IntroductionWater-assisted injection molding technology [1] has proved itself a breakthrough in the manufacture of plastic parts due to its light weight, faster cycle time, and relatively lower resin cost per part. In the water-assisted injection molding process, the mold cavity is partially filled with the polymer melt followed by the injection of water into the core of the polymer melt. A schematic diagram of the water-assisted injection molding process is illustrated in Fig. 1.Water-assisted injection molding can produce parts incorporating both thick and thin sections with less shrink-age andwarpage and with a better surface finish, but with a shorter cycle time. The water-assisted injection molding process can also enable greater freedom of design, material savings, weight reduction, and cost savings in terms of tooling and press capacity requirements [2–4]. Typical applications include rods and tubes, and large sheet-like structural parts with a built-in water channel network. On the other hand, despite the advantages associated with the process,the molding window and process control are more critical and difficult since additional processing parameters are involved. Water may also corrode the steel mold, and some materials including thermoplastic composites are difficult to mold successfully. The removal of water after molding is also a challenge for this novel technology. Table 1 lists the advantages and limitations of water-assisted injection molding technology.Fig. 1. Schematic diagram of water-assisted injection molding process.Water assisted injection molding has advantages over its better known competitor process, gas assisted injection molding [5], because it incorporates a shorter cycle time to successfully mold a part due to the higher cooling capacity of water during the molding process. The incompressibility,low cost, and ease of recycling the water makes it an ideal medium for the process. Since water does not dissolve and diffuse into the polymer melts during the molding process, the internal foaming phenomenon [6] that usually occurs in gas-assisted injection molded parts can be eliminated.In addition, water assisted injection molding provides a better capability of molding larger parts with a small residual wall thickness. Table 2 lists a comparison of water and gas assisted injection molding.With increasing demands for materials with improved performance, which may be characterized by the criteria of lower weight, higher strength, and a faster and cheaper production cycle time, the engineering of plastics is a process that cannot be ignored. These plastics include thermoplastic and thermoset polymers. In general, thermoplastic polymers have an advantage over thermoset polymers in popular materials in structural applications.Poly-butylene-terephthalate (PBT) is one of the most frequently used engineering thermoplastic materials, whichis formed by polymerizing 1.4 butylene glycol and DMT together. Fiber-reinforced composite materials have been adapted to improve the mechanical properties of neat plastic materials. Today, short glass fiber reinforced PBT is widely used in electronic, communication and automobile applications. Therefore, the investigation of the processing of fiber-reinforced PBT is becoming increasingly important[7–10].Thisreport was made to experimentally study the waterassisted injection molding process of poly-butylene-terephthalate (PBT) materials. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The materials included a virgin PBT and a 15% glass fiber filled PBT composite, and a plate cavity with a rib across center was used. Various processing variables were examined in terms of their influence on the length of water penetration in molded parts, which included melt temperature, mold temperature, melt filling speed, short-shot size, water pressure, water temperature,water hold and water injection delay time. Mechanical property tests were also performed on these molded parts,and XRD was used to identify the material and structural parameters. Finally, a comparison was made betweenwater-assisted and gas-assisted injection molded parts.Table 12. Experimental procedure2.1. MaterialsThe materials used included a virgin PBT (Grade 1111FB, Nan-Ya Plastic, Taiwan) and a 15% glass fiber filled PBT composite (Grade 1210G3, Nan-Ya Plastic, Taiwan).Table 3 lists the characteristics of the composite materials.2.2. Water injection unitA lab scale water injection unit, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit, was used for all experiments [3]. An orifice-type water injection pin with two orifices (0.3 mm in diameter) on the sides was used to mold the parts. During the experiments, the control circuit of the water injection unit received a signal from the molding machine and controlled the time and pressure of the injected water. Before injection into the mold cavity, the water was stored in a tank with a temperature regulator for 30 min to sustain an isothermal water temperature.2.3. Molding machine and moldsWater-assisted injection molding experiments were conducted on an 80-tonconventional injection-molding machine with a highest injection rate of 109 cm3/s. A plate cavity with a trapezoidal water channel across the center was used in this study. Fig. 2 shows the dimensions ofthe cavity. The temperature of the mold was regulated by a water-circulating mold temperature control unit. Various processing variables were examined in terms of their influence on the length of water penetration in water channels of molded parts: melt temperature, mold temperature, meltfill pressure, water temperature and pressure, water injection delay time and hold time, and short shot size of the polymer melt. Table 4 lists these processing variables as well as the values used in the experiments.2.4. Gas injection unitIn order to make a comparison of water and gas-assisted injection molded parts, a commercially available gas injection unit (Gas Injection PPC-1000) was used for the gas assisted injection molding experiments. Details of the gas injection unit setup can be found in the Refs. [11–15].The processing conditions used for gas-assisted injection molding were the same as that of water-assisted injection molding (terms in bold in Table 4), with the exception of gas temperature which was set at 25 C.2.5. XRDIn order to analyze the crystal structure within the water-assisted injection-molded parts, wide-angle X-ray diffraction (XRD) with 2D detector analyses in transmission mode were performed with Cu Ka radiation at 40 kV and 40 mA. More specifically, the measurements were performed on the mold-side and water-side layers of the water-assisted injection-molded parts, with the 2h angle ranging from 7 to 40 . The samples required for these analyses were taken from the center portion of these molded parts. To obtain the desired thickness for the XRD samples, the excess was removed by polishing theTable 3samples on a rotating wheel on a rotating wheel, first with wet silicon carbide papers, then with 300-grade silicon carbide paper, followed by 600- and 1200-grade paper fora better surface smoothness.2.6. Mechanical propertiesTensile strength and bending strength were measured on a tensile tester. Tensiletests were performed on specimens obtained from the water-assisted injection molded parts (see Fig. 3) to evaluate the effect of water temperature on the tensile properties. The dimensions of specimens forthe experiments were 30 mm · 10 mm · 1 mm. Tensile tests were performed in a LLOYD tensiometer according to the ASTM D638M test. A 2.5 kN load cell was used and the crosshead speed was 50 mm/min.Bending tests were also performed at room temperature on water-assisted injection molded parts. The bending specimens were obtained with a die cutter from parts (Fig. 3) subjected to various water temperatures.The dimensions of the specimens were 20 mm · 10 mm · 1 mm. Bending tests were performed in a micro tensile tester according to the ASTM D256 test. A 200 N load cell was used and the crosshead speed was 50 mm/min.2.7. Microscopic observationThe fiber orientation in molded specimens was observed under a scanning electron microscope (Jeol Model 5410).Specimens for observation were cut from parts molded by water-assisted injection molding across the thickness (Fig. 3). They were observed on the cross-section perpendicular to the flow direction. All specimen surfaces were gold sputtered before observation.3. Results and discussionAll experiments were conducted on an 80-ton conventional injection-molding machine, with a highest injection rate of 109 cm3/s. A plate cavity with a trapezoidal water channel across the center was used for all experimentsTable 4Fig. 3. Schematically, the positioning of the samples cut from the molded parts for tensile and bending tests and microscopic observations.3.1. Fingerings in molded partsAll molded parts exhibited the water fingering phenomenon at the channel to plate transition areas. In addition,molded glass fiber filled composites showed more severe water fingerings than those of non-filled materials, as shown photographically in Fig. 4. Fingerings usually form when a less dense, less viscous fluid penetrates a denser,more viscous fluid immiscible with it. Consider a sharp two phase interface or zone where density and viscosity change rapidly. The pressure force (P2 P1) on the displaced fluid as a result of a virtual displacement dx of the interface can be described by [16], where U is the characteristic velocity and K is the permeability.If the net pressure force is positive, then any small displacement will be amplified and lead to an instabilityand part fingerings. For the displacement of a dense, viscous fluid (the polymer melt) by a lighter, less viscous one (water), we can have Dl = l1 l2 > 0, and U > 0 [16].In this case, instability and the relevant fingering result when a more viscous fluid is displaced by a less viscous one, since the less viscous fluid has the greater mobility.The results in this study suggest that glass fiber filled composites exhibit a higher tendency for part fingerings. This might be due to the fact that the viscosity difference Dl between water and the filled composites is larger than the difference between water and the non-filled materials. Waterassisted injection molded composites thus exhibit more severe part fingerings.Fig. 4. Photograph of water-assisted injection molded PBT composite part.3.2. Effects of processing parameters on water penetrationVarious processing variables were studied in terms of their influence on the water penetration behavior. Table 4 lists these processing variables as well as the values used in the experiments. To mold the parts, one central processing condition was chosen as a reference (bold term in TableBy changing one of the parameters in each test, we were able to better understand the effect of each parameter on the water penetration behavior of water assisted injection molded composites. After molding, the length of water penetration was measured. Figs. 5–10 show the effects of these processing parameters on the length of water penetration in molded parts, including melt fill pressure, melt temperature, mold temperature, short shot size, water temperature, and water pressure.The experimental results in this study suggest that water penetrates further in virgin PBT than in glass fiber filled PBT composites. This is due to the fact that with the reinforcing glass fibers the composite materials have less volumetric shrinkage during the cooling process. Therefore,they mold parts with a shorter water penetration length.The length of water penetration decreases with the melt fill pressure (Fig. 5). This can be explained by the fact that increasing the melt fill pressure increases the flow resistance inside the mold cavity. It is then more difficult for the water to penetrate into the core of the materials. The length of water penetration decreases accordingly [3].The melt temperature was also found to reduce the water penetration in molded PBT composite parts (Fig. 6). This might be due to the fact that increasing the melt temperature decreases viscosity of the polymer melt.A lower viscosity of the materials helps the water to packthe water channel and increase its void area, instead of penetrating further into the parts [4]. The hollow core ratio at the beginning of the water channel increases and the length of water penetration may thus decrease.Increasing the mold temperature decreases somewhat the length of water penetration in molded parts (Fig. 7).This is due to the fact that increasing the mold temperature decreases the cooling rate as well as the viscosity of the materials. The water then packs the channel and increases its void area near the beginning of the water channel,instead of penetrating further into the parts [3]. Molded parts thus have a shorter water penetration length.Increasing the short shot size decreases the length of water penetration (Fig. 8). In water-assisted injection molding, the mold cavity is partially filled with the polymer melt followed by the injection of water into the core of the polymer melt [4]. Increasing the short shot size of the polymer melt will therefore decrease the length of water penetration in molded parts.For the processing parameters used in the experiments,increasing the water temperature (Fig. 9) or the water pressure(Fig. 10) increases the length of water penetration in molded parts. Increasing the water temperature decreases the cooling rate of the materials and keeps the polymer melt hot for a longer time; the viscosity of the materials decreases accordingly. This will help the water penetratefurther into the core of the parts [3]. Increasing the water pressure also helps the water penetrate into the materials.The length of water penetration thus increases.Finally, thedeflection of molded parts, subjected to various processing parameters, was also measured by a profilemeter.The maximum measured deflection is considered as the part warpage. The result in Fig. 11 suggests that the part warpage decreases with the length of water penetration.This is due to the fact that the longer the water penetration,the more the water pressure can pack the polymeric materials against the mold wall. The shrinkage as well as the relevant part warpage decreases accordingly.Fig. 5. Effects of melt fill pressure on the length of water penetration in molded parts.Fig. 6. Effects of melt temperature on the length of water penetration in molded parts.Fig. 9. Effects of water temperature on the length of water penetration in moldedparts.Fig. 7. Effects of mold temperature on the length of water penetration in molded parts.Fig. 8. Effects of short shot size on the length of water penetration inmolded parts.Fig. 10. Effects of water pressure on the length of water penetration inmolded parts.3.3. Crystallinity of molded partsPBT is a semi-crystalline thermoplastic polyester with a high crystallization rate. In the water-assisted injection molding process, crystallization occurs under non-isothermal conditions in which the cooling rate varies with cooling time. Here the effects of various processing parameters(including melt temperature, mold temperature, and water temperature) on the level of crystallinity in molded parts were studied. Measurements were conducted on a wideangle X-ray diffraction (XRD) with 2D detector analyses(as described in Section 2). The measured results in Fig. 12 showed that all materials at the mold-side lay erexhibited a higher degree of crystallinity than those at the water-side layer. The result indicates that the water has a better cooling capacity than the mold during the cooling process. This matches our earlier finding [17] by measuring the in-mold temperature distribution. In addition, the experimental result in Fig. 12c also suggests that the crystallinity of the molded materials generally increases with the water temperature. This is due to the fact that increasing the water temperature decreases the cooling rate of the materials during the cooling process. Molded parts thus exhibited a higher level of crystallinity.On the other hand, to make a comparison of the crysallinity of parts molded by gas and water, gas-assisted injection molding experiments were carried out on the same injection molding machine as that used with water, but equipped with a high-pressure nitrogen gas injection unit [11–15]. The measured results in Fig. 13 suggests that gas-assisted injection molded parts have a higher degree of crystallinity than water-assisted injection mold parts.This is due to the fact that water has a higher cooling capacity and cools down the parts faster than gas. Parts molded by water thus exhibited a lower level of crystallinity than those molded by gas.Fig. 11. Measured warpage of molded parts decreases with the length of waterpenetration.3.4. Mechanical propertiesTensile tests were performed on specimens obtained from the water-assisted injection molded parts to examine the effect of water temperature on the tensile properties.Fig. 14 showed the measured decrease subjected to various water temperatures. As can be observed, both yield strength and the elongational strain at break of water assisted molded PBT materials decrease with the water temperature. On the other hand, bending tests were also performed at room temperature on water-assisted injection molded parts. The measured result in Fig. 15 suggests that the bending strength of molded parts decreases with the water temperature.Increasing the water temperature generally decreases the cooling rate and molds parts with higher level of crystallin-content of free volume and therefore an increasing level of stiffness. However, the experimental results here suggest that the quantitative contribution of crystallinity to PBT’s mechanical properties is negligible, while there is a more important quantitative increase of tensile and bending strength for the PBT materials. The mechanical properties of molded materials are dependent on both the amount and the type of crystalline regions developed during processing.The fact that the ductility of PBT decreases with the degree of crystallinity may indicate that a more crystalline and stiffer PBT developed at a lower cooling rate during processing and did not exhibit higher stress values in tensile tests because of a lack of ductility, and therefore did not behave as strong as expected from their stiffness [18]. Nevertheless,more detailed experiments will be needed for the future works to investigate the morphological parameters of water-assisted injection molded parts and their correlation with the parts’ mechanical properties.3.5. Fiber orientation in molded partsSmall specimens were cut out from the middle of molded parts in order to observe their fiber orientation. The position of the specimen for the fiber orientation observation is as shown in Fig. 3. All specimen surfaces were polished and gold sputtered before observation. Fig. 16 shows the microstructure of the water-assisted injection molded composite parts. The measured result suggests that the fiber orientation distribution in water-assisted injection molded parts is quite different from that of conventional injection ity. As is usually encountered in semi-crystalline thermoplastics,a higher degree of crystallization means a lower molded parts.Inconventional injection molded parts, two regions are usually observed: the thin skin and the core. In the skin region near the wall, all fibers are oriented parallel to the injection molding, water-assisted injection molding technology is different in the way the mold is filled. With a conventional injection molding machine, one cycle is characterized by the phases of filling, packing and cooling.In the water-assisted injection molding process, the mold cavity is partially filled with the polymer melt followed by the injection of water into the core of the polymer melt.The novel filling process influences the orientation of fibers and matrix in a part significantly.From Fig. 16, the fiber orientation in water-assisted injection molded parts can be approximately divided intothree zones. In the zone near the mold-side surface where the shear is more severe during the mold filling, fibers are principally parallel. For the zone near the water-side surface,the shear is smaller and the velocity vector greater.In this case, the fiber tends to be positioned more transversely in the direction of injection. At the core, the fibers tend to be oriented more randomly. Generally speaking,the glass fibers near the mold-side surface of molded parts were found to be oriented mostly in the flow direction, and oriented substantially perpendicular to the flow direction with increasing distance from the mold-side surface.Finally, it should be noted that a quantitative comparison of morphology and fiber orientation [21] in waterassisted molded and conventional injection molded parts will be made by our lab in future works.Fig. 16. Fiber orientation across the thickness of water-assisted injection molded PBTcomposites.4. ConclusionsThis report was made to experimentally study the water-assisted injection molding process of poly-butylene-terephthalate(PBT) composites. The following conclusions can be drawn based on the current study.1. Water-assisted injection molded PBT parts exhibit the fingering phenomenon at the channel to plate transition areas. In addition, glass fiber filled composites exhibit more severe water fingerings than those of non-filled materials.2. The experimental results in this study suggest that the length of water penetration in PBT composite materials increases with water pressure and temperature, and decreases with melt fill pressure, melt temperature, and short shot size.3. Part warpage of molded materials decreases with the length of water penetration.4. The level of crystallinity of molded parts increases with the water temperature. Parts molded by water show a lower level of crystallinity than those molded by gas.5. The glass fibers near the surface of molded PBT composite parts were found to be oriented mostly in the flow direction, and oriented substantially perpendicular to the flow direction with increasing distance from the skin surface.玻璃纤维增强复合材料水辅注塑成型的实验研究摘要:本报告的目的是通过实验研究聚对苯二甲酸丁二醇复合材料水辅注塑的成型工艺。
注塑模具英文文献
Employing current design approaches for plastic parts will fail to produce the true minimum manufacturing cost in these cases.
Minimizing manufacturing costs for thin injection
molded plastic components
1. Introduction
In most industrial applications, the manufacturing cost of a plastic part is mainly governed by the amount of material used in the molding procend the part deformation after molding [12], analyzing the effects of wall thickness and the flow length of the part [13], and analyzing the internal structure of the plastic part design and filling materials flows of the mold design [14]. Reifschneider [15] has compared three types of mold filling simulation programs, including Part Adviser, Fusion, and Insight, with actual experimental testing. All these approaches have established methods that can save a lot of time and cost. However, they just tackled the design parameters of the plastic part and mold individually during the design stage. In addition, they did not provide the design parameters with minimum manufacturing cost. Studies applying various artificial intelligence methods and techniques have been found that mainly focus on optimization analysis of injection molding parameters [16,17]. For in-stance He et al. [3] introduced a fuzzy- neuro approach for automatic resetting of molding process parameters. By contrast , Helps et al. [18,19] adopted artificial neural networks to predict the setting of molding conditions and plastic part quality control in molding. Clearly, the development of comprehensive molding process models and computer-aided manufacturing provides a basis for realizing molding parameter optimization [3 , 16,17]. Mok et al. [20] propose a hybrid neural network and genetic algorithm approach incorporating Case-Based Reasoning (CBR) to derive initial settings for molding parameters for parts with similar design features quickly and with acceptable accuracy. Mok’s approach was based on past product processing data, and was limited to designs that are similar to previous product data. However, no real R&D effort has been found that considers minimizing manufacturing costs for thin plastic components. Generally, the current practical approach for minimizing the manufacturing cost of plastic components is to minimize the thickness and the dimensions of the part at the product design stage, and then to calculate the costs of the mold design and molding process for the part accordingly, as shown in Fig. 1. The current approach may not be able to obtain the real minimum manufacturing cost when handling thin plastic components. 1.2Manufacturing requirements for a typical thin plastic component As a test example, the typical manufacturing requirements for a thin square plastic part with a center hole, as shown in Fig. 2, are given in Table 1.
注塑模具国外文献1
Numerical analysis offlow mark surface defectsin injection moldingflowAnne M.Grillet,a)Arjen C.B.Bogaerds,and Gerrit W.M.Peters,andFrank P.T.Baaijens b)Dutch Polymer Institute,Department of Mechanical Engineering,Eindhoven University of Technology,Postbus513,5600MB Eindhoven,The NetherlandsMarkus BultersDSM Research,P.O.Box18,6160MD Geleen,The Netherlands(Received30May2001;final revision received7January2002)SynopsisIn order to elucidate the mechanism offlow mark surface defects,the stability of injection molding flow is investigated numerically using a transientfinite element method.Experiments performed by Schepens and Bulters͓Bulters,M.,and A.Schepens,‘‘The origin of the surface defect‘slip-stick’on injection moulded products,’’Paper IL-3-2,in Proceedings of the16th Annual Meeting of the Polymer Processing Society,Shenghai,China,2000a,pp.144–145͔using a novel two color injection molding technique are summarized and they indicate that surface defects are caused by a flow instability near the free surface duringfilling of the mold.Steadyfinite element calculations of a model injection moldingflow using a single mode,exponential Phan-Thien–Tanner constitutive equation supply information about the base state streamlines and polymer stresses.By varying the parameters of the model,the degree of strain hardening in the extensional viscosity can be controlled.Then a linear stability analysis is used to determine the most unstable eigenmode of the flow and the dependence on the extensional properties of the polymer.For strain softening materials,the injection moldingflow is predicted to be stable up to a Weissenberg number offive. However,the most unstable disturbance is consistent with the swirlingflow near the interface observed experimentally.For strain hardening rheologies,an instability is observed in the channel flow far from the interface,in agreement with calculations performed by Grillet et al.͓Grillet,A. M.,A.C.B.Bogaerds,G.W.M.Peters,and F.P.T.Baaijens,‘‘Stability analysis of constitutive equations for polymer melts in viscometricflows,’’J.Non-Newt.Fluid Mech.͑accepted,2001͔͒on planar Poiseuilleflow of a Phan-Thien–Tannerfluid.©2002The Society of Rheology.͓DOI:10.1122/1.1459419͔I.INTRODUCTIONFlow instabilities during injection molding can cause nonuniform surface reflectivity on a plastic product.Our research focuses on a specific surface defect that is character-ized by shiny dull bands roughly perpendicular to theflow direction which alternate on the upper and lower surfaces of the mold as shown in Fig.1.These defects,which are a͒Current address:Sandia National Laboratories,P.O.Box5800,MS0834,Albuquerque,NM87185.b͒Author to whom all correspondence should be addressed;Electronic mail:baaijens@wfw.wtb.tue.nl©2002by The Society of Rheology,Inc.J.Rheol.46͑3͒,651-669May/June͑2002͒0148-6055/2002/46͑3͒/651/19/$25.00651referred to as flow marks,tiger stripes,or ice lines,have been observed in a variety of polymer systems including polypropylene ͓Bulters and Schepens ͑2000a ͔͒,acrylonitrile-styrene-acrylate ͑ASA ͓͒Chang ͑1994͔͒,ethylene-propylene block copolymers ͓Monasse et al.͑1999͔͒and polycarbonate ͑PC ͒/acrylonitrile butadiene-styrene ͑ABS ͒blends ͓Hobbs ͑1996͒;Hamada and Tsunasawa ͑1996͔͒.The occurrence of these defects can limit the use of injection molded parts,especially in unpainted applications such as car bumpers.The nature of the alternating bands depends on the polymer material.With polypro-pylene and ASA injection molding,flow marks appear as dull,rough bands on a normally smooth,shiny surface ͓Bulters and Schepens ͑2000a ͒;Chang ͑1994͔͒.Scanning electron micrographs show that the region with flow marks has a striated surface topology that shows hills and valleys oriented in the flow direction ͓Chang ͑1994͔͒.For polymer blend systems,Hamada and Tsunasawa ͑1996͒suggested that the differences in reflectivity can also be associated with differences in the blend composition at the flow marks.During steady injection molding of PC/ABS blends,the authors noted that the polycarbonate phase seems to preferentially coat the mold wall,leaving a shiny surface ͓Hamada and Tsunasawa ͑1996͔͒.By contrast,the flow mark bands were found to contain a higher concentration of ABS and were cloudy.By selectively etching the ABS component,approximate streamline patterns could be observed on cross sections of the injection molded product ͓Hamada and Tsunasawa ͑1996͔͒.When the smooth,PC rich surface was being deposited,the blend morphology showed a symmetrically smooth flow pattern near the free surface.However,when the flow front passed through the region where flow marks were being deposited on the mold surface,the steady flow pattern near the free surface had been disrupted and was no longer symmetric ͓Hamada and Tsunasawa ͑1996͔͒.Other recent experimental findings have also concluded that the surface defects are the result of an unstable flow near the free surface similar to that shown in Fig.2͓BultersandFIG.1.Characteristic pattern for flow mark surfacedefects.FIG.2.Unstable flow may cause surface defects.652GRILLET ET AL.Schepens ͑2000a ͒;Chang ͑1994͒;Hobbs ͑1996͒;Hamada and Tsunasawa ͑1996͒;Mo-nasse et al.͑1999͔͒.The two most common mechanisms that have been proposed for unstable flow are slip at the wall ͓Chang ͑1994͒;Hobbs ͑1996͒;Monasse et al.͑1999͔͒or instability at the point of stagnation ͓Bulters and Schepens ͑2000a ͒;Monasse et al.͑1999͔͒.Due to the limited availability of rheological data,there is no clear understand-ing of the rheological dependence of the instability,although Chang ͑1994͒found that materials with a higher recoverable shear strain (S R ϭN 1/2xy )had less severe flow mark surface defects.A similar unstable flow was postulated to explain the transfer of pigments during injection molding of high density polyethylene ͓Reilly and Price ͑1961͔͒.If a small amount of red pigment or crayon were placed on one mold surface,a transfer mark would be present on the opposite wall downstream of the original mark.The transfer was attributed to an ‘‘end-over-end’’flow pattern which was found to depend on the injection speed and mold thickness.The type of polymer was also important because transfer marks were not observed for a cellulose acetate or a polystyrene polymer ͓Reilly and Price ͑1961͔͒.Wall slipping has been proposed as a possible mechanism for the transfer marks ͓Denn ͑2001͔͒,but they may also have been caused by the same flow instability that causes flow mark surface defects ͓Wissbrun ͑2001͔͒.Because of the complexity of the industrial injection molding process ͑three-dimensional,nonisothermal flow;fully elastic material rheology with many time scales;crystallization;fiber or particulate reinforcement ͒it is not possible to address every aspect fully ͓Isayev ͑1987͔͒.There has been a large amount of work that has focused on different components of the complete injection molding process.For example,the kine-matics of injection molding of inelastic shear thinning materials are fairly well under-stood ͓Isayev ͑1987͔͒.Whereas no simulations have been performed to specifically in-vestigate flow mark surface defects,the fountain flow near the advancing free surface ͑where stagnation point instability has been postulated ͒has been investigated,initially by Rose in 1961.As fluid elements move towards the advancing interface,they ‘‘spill over towards the wall region being vacated by the advancing interface’’͓Rose ͑1961͔͒as illustrated in Fig.3͑a ͒.The effect of fountain flow on quenched stresses in injection molded products was examined in detail by Tadmor ͑1974͒and more recently by Mavridis et al.͑1988͒.The deformation history of the fluid elements in the fountain flow can have a significant impact on the molecular orientation and trapped stresses in an injection molded product.This is especially true in the surface layer since material which is deposited on the mold’s surface with the polymers in a stretched state will rapidly be cooled and create a ‘‘skin layer’’with high residual stress.Material in the core region cools more slowly so the polymer stretch and orientation can relax ͓Mavridis et al.͑1988͒;Tadmor ͑1974͔͒.Since it is the skin layer which determines surface reflectivity,the uniformity of the elonga-tional flow at the point of stagnation will have a direct impact on surfacequality.FIG.3.Kinematics of the fountain flow region:reference frame of ͑a ͒the mold and ͑b ͒the moving interface.653FLOW MARK SURFACE DEFECTS654GRILLET ET AL.There can be significant difficulties in incorporating elasticity into simulations of freesurfaceflow because of the geometric‘‘stick–slip’’singularity that exists at the point ofcontact where the free surface intersects the mold wall,as summarized by Shen͑1992͒.Elastic constitutive equations are known to make geometric singularities more severe ͓Grillet et al.͑1999͒;Hinch͑1993͔͒.In order to make elastic injection molding simula-tions tractable,many researchers have incorporated slip along the wall near the singular-ity͓Sato and Richardson͑1995͒;Mavridis et al.͑1988͔͒.Various formulations for a slipcondition do not seem to have a strong effect on the kinematics in the free surface,but allseem to ease the difficulties associated with numerical calculations,especially for elasticconstitutive equations͓Mavridis et al.͑1986͒;Mavridis et al.͑1988͒;Shen͑1992͔͒.Perhaps due to the difficulties associated with the geometric singularity,there havebeen few fully elastic simulations of injection moldingflow͑i.e.,coupled velocity andstress calculations with an elastic constitutive equation͓͒Kamal et al.͑1988͔͒.Mostsimulations have instead assumed Newtonianflow or otherwise used constitutive modelswhich incorporated shear thinning,but not elastic effects such as the power law model ͓Tadmor͑1974͒;Mavridis et al.͑1986͔͒.The few studies which have used more realistic constitutive equations such as the Leonov model͓Mavridis et al.͑1988͔͒;the White–Metzner model͓Kamal et al.͑1986͒͑1988͔͒,and the Oldroyd-B model͓Sato and Rich-ardson͑1995͔͒mostly focused on modeling the deformation of tracer particles by the fountainflow or predicting quenched elastic stresses in thefinal product;they unfortu-nately did not investigate the stresses in fountainflow.As for other complexflows such asflow around a cylinder,there have been numerous studies using various numerical methods and viscoelastic constitutive equations and they are summarized in a recent review by Baaijens͑1998͒.We have performed steady,transientfinite element simulations of a viscoelasticfluidin a simplified injection moldingflow to investigate the occurrence offlow mark surfacedefects.A fully implicit DEVSS-G/SUPG method which was thoroughly tested on planarflows of viscoelastic materials͓Grillet et al.͑in press͔͒is applied to the modelflow.Theexponential version of the Phan-Thien–Tanner constitutive equation was chosen becauseit can qualitatively capture the rheology of polymer melts͓Larson͑1988͔͒.By varyingthe parameters of the model,melts ranging from strain hardening to strain softening inextensionalflow can be investigated for their effect on fountainflow.Before discussingdetails of the simulations,we review some recent experiments onflow mark surfacedefects which were instrumental in the design of the simulations͓Bulters and Schepens ͑2000a,2000b͔͒.II.EXPERIMENTAL RESULTSA series of injection molding experiments were carried out on several commercial, impact modified polypropylene compounds͑DSM͒.The tests were performed on a stan-dard bar shaped ruler mold with a length of300mm long,30mm wide,and3mm thick. The frequency and severity of theflow mark surface defects were recorded as a function of several molding parameters including the mold and melt temperatures and the mold design as well as geometric factors such as the mold width,the injection screw diameter, and the buffer size.From the results,several potential mechanisms which had been proposed to explain the occurrence offlow marks were discarded.Because the defects did not depend on the buffer size or screw and nozzle geometry,the possibility of upstream instability in the nozzle or gate was ruled out.The mold surface was modified by coating the mold with a very thin layer of silicone oil or coating one side of the mold with fluoropolymer,but this had no effect on the frequency of the surface defect so slip at thewall was discarded as the cause of the flow marks.That left the possibility of an insta-bility during filling of the mold.To further investigate this as a possible mechanism,a new two color injection molding technique was developed.The ruler mold was filled with a polymer whose bottom 47%had been dyed black.If the flow is stable,white material should flow along the symmetry line in the center towards the free surface where it will be split by the point of stagnation,leaving a thin coating on the top and bottom surfaces of the bar.Instead,the surface of the bar displayed alternating black and white strips which corresponded both in location and frequency to the surface defects in the original experiments ͑Fig.4͒.This technique allows investigation of the causes of surface defects,independent of the crystallization behavior,once the polymer begins to solidify on the cold mold wall.Short-shot experiments were also performed using the two color injection molding technique.Fittings were placed in the mold that allowed the ruler mold to be filled only partially.These experiments were carried out using a block of white polymer with a thin strip of black polymer along its centerline.The results for a series of tests where the mold was filled to different volume fractions is shown in Fig.5.In a stable flow,the black material should coat both mold surfaces.However,instead of the symmetric fountain flow pattern expected at the interface,the black strip is first swept to the bottom then flipped around to the top.The alternating colors of the surface coating match exactly the black and white stripped pattern observed when the mold is completely filled.Theoscil-FIG.4.Two color injection molding experiment ͑above ͒compared with a traditional injection molded sample ͑below ͒.FIG.5.Short shots with two color injection molding of a filled polypropylene compound.655FLOW MARK SURFACE DEFECTSlatory flow pattern has also been confirmed using a high speed video of the mold filling process using a thin colored stripe injected along the centerline of a clear matrix.These results clearly strengthen the argument that surface defects are caused by instability in the fountain flow.The effects of the flow instability are only apparent in the fountain flow region and in the thin skin layer on the surface of the finished product.The channel flow far from the free surface remains free of instability.Using these two color injection molding experiments,the dependence of the instability on various parameters was reexamined.One surprising result is that the instability does not depend on the mold temperature.However,the visibility of the surface defects in traditional injection molding experiments is strongly dependent on the mold temperature.For high enough mold temperatures,the surface defect disappears because the polymers are able to relax before they solidify,but the two color injection molding shows that flow instability is not affected.These experimental results have led us to make several simplifying assumptions when designing the model injection molding problem for our numerical simulations.We will focus on two-dimensional injection molding flow.Since the instability does not depend on the temperature of the mold wall,isothermal calculations will be performed,neglect-ing temperature effects.Also,the interface is assumed to be a nondeformable semicircle.These are assumptions which we make so that transient simulations for an elastic con-stitutive equations are tractable with the computer resources which are available.III.FINITE ELEMENT SIMULATIONSFor inertialess,incompressible flows,the dimensionless equations of the conservation of mass and momentum can be written asٌ•u ϭ0,͑1ٌ͒•⌸ϭ0,͑2͒where u is the velocity vector.The components of the Cauchy stress tensor ⌸can be separated as ⌸ϭϪpI ϩin terms of the pressure p and the polymer stress .To complete the governing equations,a constitutive equation which relates the poly-mer stress to the rate of deformation must be defined.The dimensionless upper convected form of the exponential Phan-Thien–Tanner constitutive equation for a polymer melt isWi ٌϩexp ͓Wi tr ͔͑͒ϭD ,͑3͒where is a parameter,and D ϭٌu ϩ(ٌu )T is the rate of strain tensor.The upper convected derivative is defined asٌϭץץt ϩu •ٌϪ•ٌu Ϫٌ͑u ͒T •.͑4͒The Weissenberg number is based on the average shear rate across the channel far from the free surface asWi ϭU H ͑5͒in terms of the mean velocity U and the half channel height H .These equations have been nondimensionalized by H,U ,and the zero shear viscosity.We focus on the upper con-vected form of the Phan-Thien–Tanner model because the use of the full form that incorporates the Gordon–Schowalter derivative causes a maximum in the shear stress as a function of the shear rate for some parameter values.Such a maximum has never been656GRILLET ET AL.observed experimentally and results in a discontinuous velocity profile in Poiseuille flow ͓Alves et al.͑2001͒;Larson ͑1988͒;Saramito ͑1995͔͒.We examine several values of the adjustable parameter (ϭ0.05,0.3,0.9)which controls the degree of strain hardening in extension and also the onset of shear thinning of the shear properties as shown in Fig.6.The linear viscoelastic parameters were held fixed for the three rheologies.Although multiple modes are usually required to capture the rheology of real ͑polydisperse ͒poly-mer melts ͓Larson ͑1988͔͒,the present calculations to develop and test the numerical method use a single mode which admittedly can only qualitatively predict melt rheology.Multimode model calculations would be required to make quantitative comparison with experiments.For our finite element calculations,the governing equations are written in a weak formulation using the stabilized,consistent DEVSS-G/SUPG method ͓Brooks and Hughes ͑1982͔͒.We have chosen this method because it has been shown to have excel-lent convergence properties in steady flow calculations in complex geometries ͓Baaijens͑1998͒;Brooks and Hughes ͑1982͒;Grillet et al.͑in press ͒,Gue ´nette and Fortin ͑1995͒;King et al.͑1988͒;Talwar et al.͑1994͔͒.ͩϩh͉u ͉u •,Wi ٌϩexp ͓Wi tr ͔͑͒ϪD ͪϭ0,͑6͒͑v ,ϩD ϪG ϪG T ͒Ϫٌ͑•v ,p ͒ϭ0,͑7͒͑p ,ٌ•u ͒ϭ0,͑8͒͑G ,G Ϫٌu ͒ϭ0,͑9͒with h the characteristic element size and ͑a,b ͒denotes the L 2inner product over the problem domain ͐⍀abd ⍀.The polynomial spaces are chosen in the usual manner forlow order finite elements to satisfy the Babusˇka–Brezzi ͑inf-sup ͒condition and for com-patibility of the constitutive equation at stationary points:v is biquadratic whereas ,p ,and G are bilinear ͓King et al.͑1988͒;Talwar et al.͑1994͔͒.For steady base state flow calculations,the transient term in the upper convected derivative is ignored,and the equations are solved using a Newton iteration discussed earlier by others ͓Grillet et al.͑1999,in press ͒;King et al.͑1988͒;Talwar et al.͑1994͔͒.For the transient calculations,we treat the time derivative implicitly following Brown et al.͑1993͒.Both steadyand FIG.6.Rheology of several model Phan-Thien–Tanner fluids with different values of :͑a ͒steady shear and ͑b ͒planar extension.657FLOW MARK SURFACE DEFECTSstability parts of this numerical method have been benchmarked on two planar flows previously ͓Grillet et al.͑in press ͔͒.To determine the stability of the flow once the steady solution X ˜ϭ(u ˜,˜,p ˜,G˜)is attained,we employ a linear stability analysis.A small perturbation ␦ϭ(uˆ,ˆ,p ˆ,G ˆ)T is added to the discretized governing equations ͓Eqs.͑6͒–͑9͔͒and second order terms and higher are neglected.The resulting evolution equations for the perturbation variables are then solved as a function of time starting with a random initial perturbation to the polymer stresses.The transient calculations are continued until the L 2norm of the per-turbation variables displays a constant growth or decay rate,or the magnitude of the perturbation has decreased below 10Ϫ5.The constant growth or decay rate indicates that the transient calculation has isolated the most unstable eigenvalue or,more precisely,the eigenvalue with the largest ͑although not necessarily positive ͒real part of the eigenvalue.A typical mesh ͑M41͒used for the calculations is shown in Fig.7.Constant velocity boundary conditions are imposed on the mold walls:u ͑y ϭϮ1͒ϭϪU .͑10͒For the moderate Weissenberg numbers used in this study ͑up to Wi ϭ5͒,local slip boundary conditions near the point of contact were not needed for this constitutive equa-tion,perhaps because both the shear and extensional viscosities thin at high shear or strain rates.Other constitutive models such as the upper convected Maxwell model or the Giesekus model do exhibit difficulties with singularity in the form of a low limiting Weissenberg number (W i Ϸ2)beyond which calculations fail to converge and thus would require a local slip boundary condition.Also note that the mesh resolution in the neighborhood of the contact point is rather coarse since we have not attempted to resolve the singularity.Since the instability is believed to occur in the fountain flow upstream of the contact point,the behavior of the stability should not depend on the specific treatment of the contact point.The free surface is a nondeformable,impenetrable,semicircular slip surface ͑i.e.nor-mal velocity set to zero,but no boundary condition imposed on the tangential velocity ͒.In simulations in the literature that have a deformable interface it was found that,even for shear thinning or elastic constitutive equations,the free surface shape stays nearly semi-circular ͓Kamal et al.͑1988͔͒.The stresses normal to the free surface are found to be small,although nonzero,except near the point of contact.Thus,we feel that the semicir-cular shape,while not perfect,is a reasonable assumption for our simplified model flow.The inlet boundary conditions are handled in a unique way.Instead of specifying the known velocity profile for Poiseuille flow of a Phan-Thien–Tanner fluid,we instead impose periodic boundary conditions over the part of the channel marked by the thick lines in Fig.7.To explain how this is implemented,we begin by writing the momentum equation for the nodes along the periodic boundary condition in an isolatedchannel.FIG.7.Typical finite element mesh containing 748elements.The locations of the periodic boundary conditions are shown by the thicker vertical lines.658GRILLET ET AL.͑v ,ϩD ϪG ϪG T ͒Ϫٌ͑•v ,p ͒ϩ͵⌳PBC v ⌸•n d ⌳ϭ0,͑11͒where ⌸ϭϪpI ϩis the total stress,and n is the outward pointing normal vector of the element boundary.The boundary integral is performed over both sides of the channel’s periodic boundary ⌳PBC .Because the velocities and stresses are identical across the periodic boundary,the boundary integral reduces to͵⌳PBC v ⌸•n d ⌳ϭ͑p outlet Ϫp inlet ͒͵⌳PBC v n d ⌳.͑12͒When one side of the periodic boundary condition ͑PBC ͒is inside the geometry like in our model injection molding flow,we must include an additional boundary integral over the inlet to the fountain flow section ͑i.e.,the sides of the elements along the right half of the internal periodic boundary ͒.Then the momentum equation is͑v ,ϩD ϪG ϪG T ͒Ϫٌ͑•v ,p ͒ϩ⌬p ͵⌳PBC v nd ⌳ϩ͵⌳internal v ⌸•nd ⌳ϭ0.͑13͒This would be sufficient if the flow were driven by specifying the pressure drop ⌬p between the periodic boundaries.However,to specify the driving force as a total flux through the channel,the pressure drop ⌬p is replaced by a Lagrange multiplier l and an additional equation is added for the flux Q across the inlet.͑v ,ϩD ϪG ϪG T ͒Ϫٌ͑•v ,p ͒ϩl ͵⌳PBC v ⌸•nd ⌳ϩ͵⌳internal v ⌸•nd ⌳ϭ0,͑14͒͵inlet u •nd ⌳ϭQ .͑15͒The Lagrange multiplier,and hence the pressure drop,is determined during the calcula-tion.This formulation was chosen to simplify future comparison to injection molding experiments where generally the injection speed is known and also to simplify the sta-bility calculations.To validate our calculations,meshes of different lengths and levels of refinement were used ͑Table I ͒.The coarsest mesh,M3,was not sufficient to resolve the steady flow of the shear thinning Phan-Thien–Tanner model at moderate Weissenberg numbers (Wi Ͼ2).Since the stability calculations are the most demanding,data demonstrating convergence for the more refined meshes will be shown in Sec.III B.Unless otherwise TABLE I.Characteristics of the meshes used in the finite element com-putations.MeshLength ⌬y No.of Elements M390.2172M4l120.1748M4ll140.1968M4lt220.11188M690.06671608659FLOW MARK SURFACE DEFECTS660GRILLET ET AL.stated,the results presented here were taken from our medium refined mesh͑M41͒except for the lowest value ofϭ0.05when a longer channel͑M4lt with lengthϭ22͒wasrequired for the stresses to fully develop between the fountainflow and the periodicboundary conditions at the highest Weissenberg numbers.A.Steady resultsWe begin by presenting steady results for a range ofparameters shown in Figs.8–10 for Wiϭ3.0.In Fig.8for the strain hardening material withϭ0.05,we note thestrong buildup of stress near the stagnation point on the free surface and also near thepoint of contact where the free surface intersects the moving wall.The relaxation of thestresses downstream of the interface enhances theflow near the free surface as shown bythe compression of the streamlines towards the wall relative to the fully developedflowfar from the free surface.Asis increased to0.3,the onset of shear thinning is shifted towards lower Weissen-berg numbers and the material also becomes more strain softening.These trends arereflected in both the stream function contours and the stresses.Due to the increased shearthinning,the velocity profile becomes more plugflow like in the pressure drivenflow farfrom the interface and the velocity gradients are concentrated near the walls.Looking attheflow near the free surface,we note that the streamlines are shifted away from theinterface and the strain rate near the stagnation point drops due to the strain softeningextensional viscosity.This shift is also reflected in the polymer stress components.The maximum in theyy stress has moved downstream of the stagnation point.As mentioned previously,the stresses downstream of the singularity decay more quickly for highervalues ofallowing the Poiseuilleflow in the channel to reach equilibrium in fewerchannel lengths.Hence the meshes used for this rheology are shorter than those required for the strain hardening material withϭ0.05.For the most strain softening rheology ofϭ0.9shown in Fig.10,the effects ofstrain softening and shear thinning are enhanced relative to those in the previous case of ϭ0.3,but the trends are entirely consistent.We note that the maximum in theyy component of the stress is almost a half channel height away from the free surface.Theflow is even more plug like,hence the almost equally spaced streamlines in the center ofthe channel.Observing the streamline patterns near the free surface,there is almost noneof the streamline compression near the wall that was observed for the strain hardeningrheology.These differences in extensional rheology can be summarized by examining thetangential velocity and its gradient along the free surface shown in Fig.11.For the strain hardening rheology(ϭ0.05),the strain rate along the free surface is almost constant near the stagnation point(⑀Ϸ0.3U/H)then increases close to the contact point(ϭ/2).For the strain softening rheologies,the effective shear and extensional viscosi-ties in the neighborhood of the singularity are very low,so the material along the inter-face is not effectively accelerated.The result is a lower strain rate along the interface and a large peak near the point of contact.Forϭ0.9the average strain rate near the stagnation point has dropped to⑀˙Ϸ0.1U/H.B.Stability resultsOnce steady results are obtained,a linear stability analysis is performed for each case. By tracking the norm of the perturbation as a function of time,demonstrated in Fig.12 forϭ0.90,the stability of theflow can be determined.For this case,the initial per-turbation introduced at time equals zero decays showing that theflow is stable͑i.e.,the real part of the eigenvalue is negative͒.The initial decay of the perturbation is very rapid。
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Employing current design approaches for plastic parts will fail to produce the true minimum manufacturing cost in these cases.
The demand for small and thin plastic components for miniaturization assembly has considerably increased in recent years.
Other factors besides minimal material usage may also become important when manufacturing thin plastic components.
1
sink mark [11] and the part deformation after molding [12], analyzing the effects of wall thickness and the flow length of the part [13], and analyzing the internal structure of the plastic part design and filling materials flows of the mold design [14]. Reifschneider [15] has compared three types of mold filling simulation programs, including Part Adviser, Fusion, and Insight, with actual experimental testing. All these approaches have established methods that can save a lot of time and cost. However, they just tackled the design parameters of the plastic part and mold individually during the design stage. In addition, they did not provide the design parameters with minimum manufacturing cost. Studies applying various artificial intelligence methods and techniques have been found that mainly focus on optimization analysis of injection molding parameters [16,17]. For in-stance He et al. [3] introduced a fuzzy- neuro approach for automatic resetting of molding process parameters. By contrast , Helps et al. [18,19] adopted artificial neural networks to predict the setting of molding conditions and plastic part quality control in molding. Clearly, the development of comprehensive molding process models and computer-aided manufacturing provides a basis for realizing molding parameter optimization [3 , 16,17]. Mok et al. [20] propose a hybrid neural network and genetic algorithm approach incorporating Case-Based Reasoning (CBR) to derive initial settings for molding parameters for parts with similar design features quickly and with acceptable accuracy. Mok’s approach was based on past product processing data, and was limited to designs that are similar to previous product data. However, no real R&D effort has been found that considers minimizing manufacturing costs for thin plastic components. Generally, the current practical approach for minimizing the manufacturing cost of plastic components is to minimize the thickness and the dimensions of the part at the product design stage, and then to calculate the costs of the mold design and molding process for the part accordingly, as shown in Fig. 1. The current approach may not be able to obtain the real minimum manufacturing cost when handling thin plastic components. 1.2Manufacturing requirements for a typical thin plastic component As a test example, the typical manufacturing requirements for a thin square plastic part with a center hole, as shown in Fig. 2, are given in Table 1.
Thus, current approaches for plastic part design and manufacturing focus primarily on establishing the minimum part thickness to reduce material usage.
Minimizing manufacturing costs for thin injection
molded plastic components
1. Introduction
In most industrial applications, the manufacturing cost of a plastic part is mainly governed by the amount of material used in the molding process.
The assumption is that designing the mold and molding processes to the minimum thickness requirement should lead to the minimum manufacturing cost.
Nowadays, electronic products such as mobile phones and medical devices are becoming ever more complex and their sizes are continually being reduced.
Thus, tackling thin plastic parts requires a new approachቤተ መጻሕፍቲ ባይዱ alongside existing mold design principles and molding techniques.
1.1 Current research
Today, computer-aided simulation software is essential for the design of plastic parts and molds. Such software increases the efficiency of the design process by reducing the design cost and lead time [1]. Major systems, such as Mold Flow and C-Flow, use finite element analysis to simulate the filling phenomena, including flow patterns and filling sequences. Thus, the molding conditions can be predicted and validated, so that early design modifications can be achieved. Although available software is capable of analyzing the flow conditions, and the stress and the temperature distribution conditions of the component under various molding scenarios, they do not yield design parameters with minimum manufacturing cost [2,3]. The output data of the software only give parameter value ranges for reference and leaves the decision making to the component designer. Several attempts have also been made to optimize the parameters in feeding [4–7], cooling [2,8,9], and ejection These attempts were based on maximizing the flow ability of molten material during the molding process by using empirical relation ships between the product and mold design parameters. Some researchers have made efforts to improve plastic part quality by Reducing the