Manufacturing Technology

制造技术基础复习基本概念、基本原理英语表达参考Review the Basic Concepts and Principles of Fundamentals of Manufacturing Technologyin EnglishCHAPTER ONE DESIGN FOR MECHANICAL PROCESS PLANNINGSection 1 Basic concepts• Production procedure of mechanical products• Process procedure of machiningElements of Process procedure of machining1 sequence 工序；2 installation 安装；3 station 工位；4 step 工步；5 pass 走刀• Sequence : process procedure that consists of several sequences during which workers operate on the works continuously in the same place;(操作者、加工地、工作对象——人为划分，相对可变)• Installation: in a sequence if the work is required to put into position and clamp several times ,the part of sequence done in one positioning and clamping is called aninstallation;(确定）• Station : In an installation, by using the indexing or moving device the work is changed its position relatively to the cutting tool. All the tasks done for the work in one machiningposition in an installation is termed as the station;(确定）• Step ：In one station if the surface cut, cutting tool, velocity, and feed remain unchanged, these working contents are thought of as the step.(加工表面、刀具、切削速度、进给量任一改变均为另一工步）• Pass: When the surface of the work is cut for any one time ,such task carried out is named as the pass• (刀具在加工表面的每一次切削）• Processing system :• a system that contains the work to be machined, fixture that holds the work in the proper position, cutting tool that machines the work directly, and machine tool that givesthe power and provide the movements to accomplish the processing. In recent years thegauging and measuring is added to the system.Relationship between the batch and the pattern of productionN-program of production, Q-annual turnout of the productn-number of the components a year,-share rate, -waste rate , F -annual working days ,A- number of days for inventory, -number of components in a lotA Program of productionIn a period of planning, the turnout of product and schedule to be fulfilled is called program. (计划期的产量加进度=生产纲领）The turnout in one year planning is named the annual program .B Batch of productionAt a time, the number of identical products to be put into production or to be producedis termed as batch of production.(一次投入生产的同一产品的数量=生产批量）Process planning for machining operations :stipulated document for technological process (机械加工工艺规程：以工艺文件形式规定的机(1%%)N =Qn αβ++b N F n =A械加工工艺过程)Patterns of the process planning for machiningGenerally speaking, the process planning for machining appears in the form of sheet or card with the same basic content in three patterns:Pattern A: sheet of process procedures (工艺过程卡), a very simple and concise document, usually for single/small batch productionPattern B: sheet of process operation (机械加工工艺卡), often for batch productionPattern C: sheet of process sequence (机械加工工序卡), with detailed and complete contents, frequently for massive productionSection 2 Location and Datum of the work in machiningInstallation and clamping(装夹）: concerning about the ways in which the work is installed and clamped in the fixture or on the machine tool, including two aspects, locating(定位) and clamping(夹紧).Locating: the procedure during which the work gains its proper position in the fixture or on the machine tool.Clamping: when the workpiece has gained its correct position in the fixture, it will be subject to the external forces while being machined. So, to hold or keep the workpiece in the correct position is definitely required, which is called clamping.Six-Point Locating Principles ：A cuboid is in cartesian coordinate with six degrees of freedomThe six degrees of freedom are three linear movements along the three coordinate axes, respectively, and three rotations around these coordinate axes In theory, the locating point is the geometric point; in reality, it is something different with its three dimensions. The following are commonly used in workshops.Button locator(支撑钉);Plug(档销); Supporting plate （支撑板）; Pin/pin locator （长销） Button; Cut pin/rhombus pin （削边销/菱形销）; Mandrel （心轴）; V block （形块）Short V block （短形块）; Positioning sleeve （定位套）; Fixed/floating conic pin （固定/浮动锥销）; Center(顶尖（固定/浮动）)Complete positioning :locating with constraint for all six degrees of freedom.Incomplete positioning : locating with constraint for less than six degrees of freedom.Under/over-positioning : the number of constraints of degree of freedom is less than that required. Under-positioning ought to be avoided and,Over-positioning : the same degree of freedom is constrained by two or even more constraining points, such situation is called over –positioning, which will be allowed occasionally.Datum(基准) is the point, line or surface based on which the geometric relation-ships among geometric elements of the object to be worked at are determined. The concept is so important that is may be used for any aspect of production, from design, through manufacturing including sequences of operation, to the gauging and assemblyTechnological/process datumsSequential datum: on the sequential drawing ,datum that is used in this sequence to determine the size, form, and position of the work after being machined is named Sequential datum. The three aspects are supposed to be taken into consideration: the priority of sequential datum is paid to the design datum, that is use the design datum as sequential datum, the selected datum is favorable for the location and the gauging of the work, and if the above requirements are hardly met, the datum used to guarantee the technical conditions.Datum may be classified into two categories,Design datum and Technological datum, according to their functions .I design datum: in design of components, the origin from which ,according to the assembly X,Y,and Z X, Y, and Zrelationship of the component and the relative relationship of the structural elements of the component itself, the dimensioning is done. These original positions are called design datums .(设计图纸上零件标注的起始位置)II technological datum: datum used in the process operations is termed technological datum, which can be even classified as:Locating datum: datum used for the workpiece to gain its proper position in machining, it directly influences the effectiveness of machining. Locating datum covers Rough datum and Finishing datum.a) Rough datum /Finishing datum : un-machined locating datum, in other word, any locating datum used in the first sequence of operation in the manufacturing process planning is the rough datum; finishing datum: machined locating datum.b) additional/auxiliary datum: the specially designed datum in the workpiece because of the requirement of the mechanical process operations.Gauging datum: during and after machining, datum used for measuring and checking the form, position, and error of size , of the workpiece.Assembling datum: in assembling datum adopted to determine the relative positions of the work or the component in the product.Section 3 Design of the routes of machining processes（工艺路线的制定）Consideration must be taken with the locating datum of the workpiece(定位基准）, the process methods（加工方法）, the order of the processes（加工顺序）, heat treatment（热处理）, testing （检验），and the related operations（其他工序）.A selection of locating datums(定位基准的选择)B selection of economic accuracy and process methods of machining（机加的经济精度与方法）C machining routes for the typical surfaces（典型表面的加工路线——外圆、孔和平面）D order of sequences（工序顺序安排）Selecting rules of rough machining datum:I guarantee the proper relative positions .II guarantee reasonable allocation of the allowance for the surface being machined .III facilitate the locating and clamping of the workpiece. For this reason, the selected surfaces as the datums must be to some extent smooth, enough-sized, flasher-free , without other defects such as reservoir and riser or the like.IV the rough locating datum used only for one time (without repetition)Selecting rules of finishing machining datum:I overlapping principle(基准重合）-datum used as the same as design datumII unifying principle（基准统一）-use the same datum as early and as frequently as possibleIII inter-reference principle（互为基准）-especially used for the high accuracy of relative positions of the surfacesIV self-reference principle（自为基准)- for sequence of small roughness, small and even allowanceV clamping-facilitating/convenient principle（便于装夹）-for proper and secure (reliable) locating, simple structure of the clamping device with easy operationEconomic accuracy in machining (经济加工精度)Under the common machining conditions , that is , with facilities and tooling in standard quality, the operators with typical skills, and in rated time ,the machining is done with the relevant accuracy and roughness imparted to the component. Such accuracy and roughness is called the economic accuracy in machiningOrder of sequences（工序顺序安排）a datum first then others;b flat first then others, generally;c the main surfaces first;d rough machining first, followed by finishing machiningCentralized, decentralizes sequences and the Machining stagesI rough machiningII semi-finishing machiningIII finishing machiningIV precision, ultra-precision ,and smooth machiningSection 4 Determination of machining allowance, dimensions between sequences, and tolerance machining allowance : the difference between the size of the blank and that of the component design on drawingthe total allowance is equal to the sum of material thickness to be removed for every step in the process operation.Sequential allowance : the thickness of metal removal of the cut layer in every sequenceThe relationship between the total allowance and Sequential allowance will be expressed in terms of Zo=Z1+Z2+…+Zn=CHAPTER TWO DESIGN PRINCIPLES OF MACHINE TOOL JIGS AND FIXTURES Section 1 introduction to the machine tool jigs and fixturesFunction, constituents, and classification （夹具的功用，组成和分类）Function: the machine tool jig or fixture is a device used in machine tool by which the workpiece obtains and keeps the proper position relative to the machine tool before and during the workpiece being machined.Constituents of the fixture : Six elements or units of a jig or fixtureI locating elements: for locating the work, such as button locator, base (body), and rhombus. II tool guide: for guiding the tool or adjusting relative position of the tool to the fixture, such as ,tool setting block.III clamping device: for holding the work firmly, such as the bolt, screw, and the heel.IV connecting elements: for determining the position of the fixture on the machine tool and connecting the fixture with the machine tool ,such as the locating key, and the base.V body: for connecting all the elements and devices as a whole, and through the body the fixture being fixed to the machine tool, such as the base.VI additions: for other purposes ,like indexing, safeguarding, error-avoiding and the like, such as the stop pin.Classification of the fixture:According to the range of usage , fixtures can generally be classified into six categories : all-purpose, special, all-purpose adjustable and group, composite, transferring fixtures.In accordance with the machine tool on which the fixture is utilized, fixtures can also be classified into lathe, milling machine, drill, borer, grinder, automatic machine tool, and NC machine tool, fixtures.Based on the power which drives the clamping devices to hold the work firmly in place, fixtures can even be classified into manual, pneumonic, hydraulic, electric-magnetic , and vacuum, fixturesSection 2 Workpiece-location in the fixture* the analysis and calculation of locating errorCommonly used methods of locating and the locating elements （the surfaces of the workpiece)A locating by flat/plane/surface （平面定位）Fixed/adjustable/self-adapted/auxiliary support(固定/可调/自位/辅助支承)Section 3 Workpiece-clamping in the fixtureRequirements of the clamping forcesDetermination of the clamping forcesnii=1ZCommonly used clamping mechanismsRequirements of the clamping forcesI sustain, during the whole period of clamping, the proper position of the workpiece when itlocatesII be reliable and proper. The clamping mechanisms are, usually, supposed to have the function of self-locking, guaranteeing the clamping device being free from relief and vibration. On the other hand, preventing ought to promise from being unwanted deformation and the damage of the surfaces.III It is taken for grant that the clamping device is convenient, not energy-consuming, and safe, to operate.IV be consistent ,for the complexity and level of automation of the clamping device, with the batch production and the pattern of productionA DirectionThe following rules should be ensured:favorable for the workpiece locatingParallel to the direction of the most rigid of the workPreferable to parallel to the direction of the cutting forces, or the gravity of the work to reduce the clamping forceB Exerting pointunder the given force, to select the point at which the clamping force actuates and the number of the exerting pointsI the exerting point coincides with the supports of the fixture or is on the supporting areabacked by the supports.II the exerting point ought to be so set that the touched area has great rigidity of the work, in order to reduce the deformation of the work possible to occur.III It is preferable to exert the clamping force at the as near place of the being cut surface as possible to eliminate the turn-over moment by the cutting forces.C Magnitude of the clamping forcesSection 4 types of machine tool mixturesDrill jigs; Borer jigs; Milling machine fixtures; Lathe fixtures; Group fixtures; Composite fixtures;Transferring fixturesCHAPTER THREE MECHANICAL PROCESS ACCURACY1 Concept of the machining accuracy and the influencing factors2 Geometric accuracy influencing the machining accuracy3 Deformation of the processing system from external forces4 Deformation of the processing system caused by heat5 Statistics and analysis, and ways of guaranteeing and enhancing the machining accuracy Section 1 Brief introduction to Machining AccuracyThe quality of a component by machining contains two-fold, one is Mechanical Process Accuracy ,and another is the Integrity of Machined Surfaces .Here we discuss the first aspect of the quality of the component .Mechanical process accurac y is the degree of the real geometry (including the size, form, and relative position between surfaces) of a workpiece imparted by machining that approaches the perfect geometry.Influencing factors of machining accuracy1)Installation of the workpiece(工件的装夹)——installing error of the workpiece（工件装夹误差）2)Adjustment of the processing system（机床、刀具和夹具的调整）——geometric error ofthe processing system（工艺系统几何误差）3)Machining operation （加工过程）——dynamic error(动误差)Sensible direction of the error: on the workpiece the initial errors vary both in magnitude and in direction, when the direction of initial error is parallel to that of the sequential size, such error has the greatest influence on the machining accuracy. So we call this direction Sensible direction of the error.Section 2 The influence of geometric accuracy of the processing system on the machining accuracyA error of principle in machining(加工原理误差)B error of adjustment (调整误差)C error of machine tools(机床误差)Guiding error of the guide-way,For a linear guide-way, the guiding accuracy includeslinearity on the horizontal plane, △y, linearity on the vertical plane, △z, parallelism between the two guide-ways δ( warp，扭曲), and the parallelism between the guide-way and the axis of the spindleRotating error of the spindleNotion：rotating accuracy of the spindle is one of the main aspects of accuracy. Rotating accuracy of the spindle influences mainly the accuracy of geometric form, position, and roughness, of the machined surfaces because of its function of installing and clamping the work or tool, and providing the primary power and machining movement.Rotating error of the spindle is the real floatation/drift of the rotating axis from the perfect rotating axis of the spindle, including radial-round flounce, facial-round flounce, and inclined-angular swing.and transmitting error of the transmission linkageD error of the fixture in its own production and wear（夹具制造误差与磨损）E error of the tool in its own production and wear（刀具制造误差与磨损）Section 3 Deformation of the processing system from external forcesBasic concept: in machining, any element or all the elements of the processing system may be subjected to cutting force, clamping force, and weight, leading to deform, and further cause machining errorsThe ability to resist the deformation is often expressed in terms of rigidity k (刚度) of the system，which means the ratio of the normal component of the cutting force to the displacement of the work in the direction of the normal component of the cutting forceSection 4 Deformation of the processing system caused by heata) Notion of the deformation from heat, and the heat balance and temperature distributionb) Influence of the deformation of the work from heat on machining accuracyc) Influence of the deformation of the tool from heat on machining accuracyd) Influence of the deformation of the machine tool from heat on machining accuracye) Ways of reducing the influence of the deformation from heat on the machining accuracy Origin of the heat:Internal heat source :mainly the cutting force and friction forces with the conductivityExternal heat source: mainly the environmental temperature with circulation, as well as heat-radiating sourcesThe cutting force is the main and important source of heatThe heat balance and the temperature fieldQgeneration+Qtakein=Qgoingoutθ=θ(x, y, z, t)→θ(x, y, z ) →deformation(x, y, z )Ways of reducing the influence of the deformation from heat on the machining accuracy1) Reducing the heat from the heat source and keeping free from the heat source2)Evening the temperature field/distribution3)Adopting the proper structure and assembling datums of the machine tool4)Speeding up the procedure of heat balance5)Controlling the surrounding temperatureSection 5 Statistics and analysis, and ways of guaranteeing and enhancing the machining accuracya) System errorIn machining a batch of components successively, if the magnitudes and directions of machining errors remain unchanged or change regularly, we call these errors system errors, and the unchanged errors are constant errors, the regularly changed errors changing errors.b) Random errorIn machining a batch of components successively, if the magnitudes and directions of machining errors are changing randomly we call these errors random/stochastic errors.Concept of ±3σis very important , and is widely used in the analysis of machining errors. 6σrepresents the machining accuracy reachable in a certain machining condition for a kind of process operation.Generally speaking, for the process chosen of a sequence, the tolerance of the sequence T and the standard difference σobey 6σ≤T.For some reason, σand μis unknown. Fortunately, we can use the total mean value of the sample , and the standard difference SUsage of the distribution graph1) Assess the feature of the machining error2) Determine the sequential ability and the level numberThe sequential ability the undulation of the machining error under steady machining conditions. If the sizes obey the normal distribution, the range of the sizes should fall into 6σ. So the sequential ability is 6σ.The level number of the sequential ability represents the degree of satisfaction to the machining accuracy, in terms of CpCp=T/ (6σ)3) Estimate the waste rate or the qualification rate.CHAPTER FOUR INTEGRITY OF MACHINED SURFACES1 Concept of the machined surface integrity and it’s influence on the component functions2 Processing factors influencing the surface roughness and the improvement3 Processing factors influencing the physical and mechanical properties of the surface layer of the component and the improvement4 Brief introduction to the vibration in machiningSection 1 Concept of the machined surface integrity and it’s influence on the component functionsA Geometric form errorsa) Surface roughness(粗糙度)：irregularities with very high frequencyb) Waviness（波度）：irregularities with high frequencyc) Lay/vein direction（纹理方向）：the direction of the marks left by the cutting tool during the forming operationsd) Scars（伤痕）：rarely presented defects on the surface, such assand pits, air hole, and cracks etc.B The physical, chemical, and mechanical properties of the surface layera) Strain hardening, with the degree and depth of the hardeningb) Metallographic compositionChanges may occur of the metallographic composition due to the cutting heat.c) Residual stress within the surface layerSection 2 Processing factors influencing the surface roughness and the improvementSection 3 Processing factors influencing the physical and mechanical properties of the surface layer of the component and the improvementA Strain hardeningThe strain hardening occurs whenever there is any form of plastic deformation, such as warp and aberrance of the crystal lattice , and slippage between the crystal grains, as well as the elongation of the crystal grains. In this procedure the surface layer gains energy and becomes hard. So we call it a strengthening procedure. However it is in the state of instability, and it will relieve if there is a chance, say absorbing (taking in) heat (weakening).B Change of the metallographic compositionC Residual stressWith factors of plastic deformation (residually compressive stress) and heat (residually tensile stress)residual stresses arising inI turning (speed, rake angle, feed ) ; II grinding( ap, v, f, work material, last sequence) Section 4 Brief introduction to the vibration in machiningForced vibration(强迫振动), self-excited vibration (quiver)（自激振动）, and free vibration（自由振动）CHAPTER FIVE DESIGN OF THE ASSEMBLING PROCESSESSection 1 Introduction to assemblyA basic concept: any machine consists of components（零件）, set of components（套件）, group or composite of components（组件）, and assembling parts(部件). And the relatively independent parts to be assembled into the machine easily and conveniently is called assembling cell or unit (装配单元).components（零件）: unit with the whole materialset of components（套件）:smallest assembling unit with a datum component and several auxiliary componentssub assembly（组件）:with a datum component and several sets of components and several auxiliary componentscomposite parts/assemblies (部件):with a datum component and several assemblies ,sets of components and auxiliary componentsOverall assembly(总装): a procedure in which a ll the components, sets of components, subassemblies and assemblies are fitted into the datum component, forming the final product, the machine.B assembling schematic（装配工艺系统图）:The draft that indicates the relationship among the components and composite parts and the assembling flow. Names, numbers and quantities are presented on the assembling schematic with panes (方格)Assembling accuracy including relative position accuracy(相互位置精度), relative moving accuracy（相对运动精度）, and fit/mating accuracy（配合精度）CHAPTER SIX:ADV ANCE AND DEVELOPMENT OF MANUFACTURING TECHNOLOGY1 Automation of mechanical manufacturing system and computer aided manufacturing (CAM/FMS/CIMs)2 Precise and ultra-precise manufacturing technology3 Non-conventional machining technology4 Other recently developed machining technology。