文献翻译—注塑模具简介

附录
THE INTRODUCTION OF MOLDING The mode is at the core of a plastic manufacturing process because its cavity gives a part its shape. This makes the mold at least as critical-and many cases more so-for the quality of the end product as, for example, the plastic unit or other components of the processing equipment.
1.1 MOLD COMPONENTS
Molds used in injection molding consist of two halves; one stationary and one movable. The stationary half is fastened directly to the stationary plate and is in direct contact with the nozzle of the injection unit during operation. The movable half of the mold is secured to the movable platen and usually contains the ejector mechanism. There are many possible mold designs, including multiple piece molds for complicated parts. On production injection molding equipment many articles may be shot at the same time by the use of multiple cavity molds. The use of a balanced runner system carries the plastic from the sprue to each individual cavity. At this point the material passes through a gate into the cavity. The gate is a restriction, smaller than the runner, to provide for even filling of the mold cavity and to allow the products to be easily removed from the runner system. With most injection molding systems, the articles can be snapped away from the runner or sprue without additional trimming. Products that have been injection molded can usually be identified by finding where the gate was broken off. The gate will usually be located at the edge or parting line of an object or in the center of cylindrical product.
Molds are expensive, as are the machines. Yet, once the product has been designed, molds made, and production started, articles can be produced in quantity at low cost. Virtually all thermoplastics can be injection molded through variations in mold and machine design.
Mold (and die) parts that are mass-produced and standardized in shape and dimension are referred to as “standards”(or, “standard parts”). Specialized operators of milling machines, lathes, electronic discharge machining (EDM) equipment and grinders produce mold components, independently of each other, following detailed mold part drawings. Finally, all these items come together with the standard mold base and hardware and are assembled by the mold maker. Today, standard components for the moldmaking industry are marketed by a number of companies.
1.2 HOT RUNNER SYSTEMS
Hot runners are classified according to the ways they are heated: insulated-runner systems (it is not described in this article) and genuine hot-runner systems.
The latter can be further sub-classified according to the types of heating: internal heating and external heating.
Heating is basically performed electrically by cartridge heaters, heating rods, band heaters, heating pipes and coils, etc. to ensure uniform flow and distribution of the melt, usually a relatively elaborate control system comprising several heating circuits and an appropriate number of sensors is needed. The operating voltage is usually 220 v to 240 v, but small nozzles frequently have a low voltage of 5 v , and also 15 v and 25 v operating voltage.
Runner systems in conventional molds have the same temperature level as the rest of the mold because they are in the same mold block. If, however, the runner system is located in a special manifold that is heated to the temperature of the melt, all the advantages listed below accrue. Runner manifolds heated to melt temperature have the task of distributing the melt as far as the gates without damage. They are used for all injection molded thermoplastics as well as for cross linking plastics, such as elastomers and thermosets.
In the case of thermoplastics, these manifolds are usually referred to as the hot-runner system, the hot manifold, or simply as hot runners. For crosslinking
plastics, they are known as cold runners.
A .Hot-Runner Systems
Hot-runner systems have more or less become established for highly-automated production of molded thermoplastic parts that are produced in large numbers. The decision to use them is almost always based on economics, i.e. production size. Quality considerations, which played a major role in the past, are very rare now because thermoplastics employed today are almost all so stable that they can be processed without difficulty with hot-runner systems that have been adapted accordingly.
Hot-runner systems are available as standard units and it is hardly worthwhile having them made. The relevant suppliers offer not only proven parts but also complete systems tailored to specific needs. The choice of individual parts is large.
B .Economic Advantages and Disadvantages of Hot-Runner Systems
1. Economic Advantages
Savings in materials and costs for regrind.
Shorter cycles; cooling time no longer determined by the slowly solidifying runners; no nozzle retraction required.
Machines can be smaller because the shot volume-arornd the runners-is redrced, and the clamping forces are smaller because the runners do not generate reactive forces since the blocks and the manifold block are closed.
2. Economic Disadvantages
Much more complicated and considerably more expensive .
More work involved in running the mold for the first time.
More susceptible to breakdowns, higher maintenance costs (leakage, failure of heating elements, and wear caused by filled materials).
3. Technological Advantages
Process can be automated (demolding) because runners do not need to be demolded.
Gates at the best postion; thanks to uniform, precisely controlled cooling of the gate system, long flow paths are possible.
Pressure losses minimized, since the diameter of the runners is not restricted.
Artificial balancing of the gate system; balancing can be performed during running production by means of temperature control or special mechanical system (e. g. adjustment of the gap in a ring-shaped die or use of plates in flow channel. Natural balancing is better).
Selective influencing of mold filling; needle valve nozzles and selective actuation of them pave the way for new technology (cascade gate system; avoidance of flow lines, in-mold decoration).
Shorter opening stroke needed with competing, conventional three-platen molds.
Longer holding pressure, which leads to less shrinkage .
4. Technological Disadvantages
Risk of thermal damage to sensitive materials because of long flow paths and dwell times, especially on long cycles .
Elaborate temperature control required because non-uniform temperature control would cause different melt temperatures and thus non-uniform filling.
C. Design of a Hot-runner System and its Components
Hot-runner molds are ambitious systems in a technological sense that involve high technical and financial outlay for meeting their main function of conveying melt to the gate without damage to the material.
D. Externally/Internally Heated System
The major advantages and disadvantages of the two types are immediately apparent from the fig.
E. Externally Heated System
1. Advantage
Large flow channels cause low flow rate and uniform temperature distribution.
2. Disadvantage
The temperatures required for external heating have to be very much higher. For PA 66, for example, the mold temperature is approximately 100 C° and the manifold temperature is at least 270 C°; this means there is a temperature difference of approximately 170 C°form the mold block, which means: Special measures required for fixing the got-runner nozzles to the gates because of the considerable thermal expansion.
Risk of disruption if this is not adequately resolved.
Higher heating power (over 500 W per 100 mm line for a typical cross-section measuing 40.7mm2) .
Insulation form the mold block.
Large, unsupported areas and therefore, with large-surfac e molds, risk of bowing of the mold platen on the feed side if this has not been designed thick enough and thus ,as a direct consequence, the mold becomes very heavy.
F. internally Heated System
A frozen layer of plastic forms on the inner surface of the channel and functions as an insulation layer.
The heat requirement of the system is much lower (rorghly 55 W per 100 mm length of inside tube)。

The temperature differences between mold and manifold blocks are negligible; therefore measures that would have been necessary for large heat expansion are not needed.
The hot manifold of an internally heated system is a compact block that is bolted tightly to the mold. Consequently, the mold is very rigid and no measures are required for centering the nozzles and gates. This also allows the plate on the
machine side to be manufactured as one block consisting of fixed mold with in-built manifold and corresponding rigidity.
The melt volume is small and so the dwell times of the flowing melt are short. On the other hand, the flow rates are very much greater and this can damage the material. It is not advisable to use internally heated systems for sensitive materials. When deciding on a certain system, advice can be obtained from suppliers.
2.1 INJECTION MOLDS
A. Basic mold design
An injection mold consists of at least two halves that are fastened to the two platens of the injection molding machine so that they can be opened and closed. In the closed position, the product-forming surfaces of the two mold halves define the mold cavity into which the plastic melt is injected via the runner system and the gate. Cooling provisions in the mold provide for cooling and solidification of the molded product so that it can be subsequently ejected.
B. Types of Ejection
For product ejection to occur, the mold must open the shape of the molded product determines whether it can be ejected simply by opening the two mold halves or whether undercuts must be present. The design of a mold is dictated primarily by the shape of the product to be molded and the provisions necessary for product ejection. Injection-molded products can be classified as:
1.Products without undercuts (e. g. plaques, strips, half-shells, cups).
2.Products with external undercuts or lateral openings (e. g. spools and
bobbins, beverage crates, threaded bolts).
3.Products with internal undercuts ( e. g. threaded closures, housings ).
4.Products with external and internal undercuts (e . g. bumper fascias,
electrical and automotive instrument housings, cameras, etc);
C.Products Without undercuts
That shows the design of an injection mold for a product without undercuts. The products are pinpoint gated on the side at 3. The mold opens at 4 upon completion of the molding cycle. The left half retracts. The products remain on the cores 5 . The sprue 6 has an undercut in the mold plate 7 that pulls it out of the sprue bushin 8. With further opening of the mold, the ejector rod 10 is actuated by the mechanical ejector in the injection machine. The ejector plate 11 comes to a stop, while the left half of the mold containing the molded products continues to the left. The ejector pins 1 attached to the ejector plate 11 now push the molded products of the cores 5. simultaneously, the pin 9 pushes the sprue 6 out of the undercut in mold plate7. The sprue 6 and molded products are ejected together. As the mold closes, the pushback pins 2 return the ejector plate 11 with the ejector pins 1 to its initial position.
D. Products with External Undercuts
That shows how the external undercut on the housing for a kitchen appliance is released. A cam pin 24 that extends into a slide 23 is attached to the stationary mold half. The slide is guided by two gibs 50 on the moving mold half. With the mold in the closed position, the slide 23 is held in place by a heel block 26 so that the cam pin 24 does not have to absorb any forces during injection. As the mold opens, the cam pin 24 pushes the slide 23 outward until the undercut on the molded product is released. A spring-loaded ball detent 2 ensures that the opened slide 23 stays in position when the cam pin 24 is pulled completely out of the guide bore in the slide. The molded product remains in the moving mold half, from which it is subsequently ejected by the ejector pins 4 and an ejector sleeve 9. As the mold closes, the ejector system and the slide 23 are returned to their original positions by the return pin 12 and cam pin 24, respectively.
E. Products with Internal Undercuts
Internal undercuts are present whenever the inside of a molded product has projections that prevent it from being stripped off the core.
Forced ejection
If the undercuts are not too deep and the molding compound is sufficiently elastic, it is quite possible to forcibly strip the molded products off the core.
The mold shown in the fag used to projecting rim that forms an undercut around proximately oval in shape and have an inward projecting rim that forms an undercut around the entire product. The elasticity of the polyethylene is utilized to release this undercut, thereby eliminating the need for a complex ejection mechanism.
Upon completion of injection, the mold opens at I. The product is withdrawn from the cavity 46 along with the core. When the ejector bar 14 is actuated, ejector plate 7 advances, via ejector rod33, plate 3 with the attached stripper ring 49(parting line II). Simultaneously, plate 8 with the attached core 47, 48 moves forward under the action of the spring 39. Plate 4 with the attached mold ring 50 remains stationary, because it is held firmly to the clamping plate 5 by the retaining strips. In this way, the molded product and core are pulled out of the mold ring 50.
After a distance W, plate 8 comes up against plate 4; core 47, 48 stops; and spring 39 is compressed further. The stripper ring continues to advance further, however, and can now strip the product off the core. During this step, the rim of the product on which stripper ring 49 acts is spread. To permit this spreading, the stripper ring cannot enclose the molded product too tightly.
2.2 THE DESIGN OF INJECTION MOLD
A. Design Rules
There are many rules for designing molds. These rules and standard practices are based on logic, past experience, convenience, and economy. For designing, mold making, and molding, it is usually of advantage to follow the rules. But occasionally, it may work out better if a rule is ignored and an alternative way is selected. In this text, the most common rules are noted, but the designer will learn only from experience which way to go. The designer must
ever be open to new ideas and methods, to new molding and mold materials that may affect these rules.
B. The Basic Mold
1.Mold Cavity Space
The mold cavity space is a shape inside the mold , “excavated”(by machining the mold material) in such a manner that when the molding material (in our case, the plastic) is forced into this space it will take on the shape of the cavity space and, therefore, the desired product. The principle of a mold is almost as old as human civilization. Molds have been used to make tools, weapons, bells, statues, and household articles, by pouring liquid metals ( iron, bronze) into sand forms. Such molds, which are still used today in foundries can be used only once because the mold is destroyed to release the product after it has solidified. Today, we are looking for permanent molds that can be used over and over. Now molds are made from strong, durable materials, such as steel, or from softer aluminum or metal alloys and even from certain plastics where a long mold life is not required because the (hot) plastic is injected into the cavity space with high pressure, so the mold must be strong enough to resist the injection pressure without deforming.
2.Number of Cavities
Many molds, particularly molds for larger products, are built for only 1 cavity space(a single-cavity mold), but many molds, especially large production molds, are built with 2 or more cavities. The reason for this is purely economical. It takes only little more time to inject several cavities than to inject one. For example, a 4-cavity mold requires only (approximately) one-fourth of the machine time of a single-cavity mold. Conversely, the production increases I proportion to the number of cavities. A mold with more cavities is more as much as a single-cavity mold. But it may also require a larger machine with larger platen area and more clamping capacity, and because it will use (in this example) 4 times the amount of plastic, it may need a larger injection unit, so the machine
hour cost will be higher than for a machine large enough for the smaller mold. Today, most multicavity molds
Are built with a preferred number is: 2,4,6,8,12,16,24,32,48,64,96,128.These numbers are selected because the cavities can be easily arranged in a rectangular pattern, which is easier for designing and dimensioning, for manufacturing, and for symmetry around the center of the machine, which is highly desirable to ensure equal clamping force for each cavity. A smaller number of cavities can also be laid out in a circular pattern, even with odd numbers of cavities, such as 3,5,7,9. It is also possible to make cavity layouts for any number of cavities, provided such rules as symmetry of the projected areas around the machine centerline are observed .
3.Cavity Shape and Shrinkage
The shape of the cavity is essentially the “negative”of the shape of the desired product, with dimensional allowances added to allow for shrinking of the plastic. The shape of the cavity is usually created with chip-removing machine tools, or with electric discharge machining (EDM),with chemical etching, or by any new method that may be available to remove metal or build it up, such as galvanic processes. It may also be created by casting (and then machining) certain metals (usually copper or zinc alloys) in plaster molds created from models of (e.g. epoxy resins). The cavity shape can be either cut directly into the mold plates or formed by putting inserts into the plates.
C. Cavity and Core
By convention, the hollow (concave) portion of the cavity space is called the cavity. The matching, often raised (or convex) portion of the cavity space is called the core. Most plastic products are cup-shaped. This does not mean that they look like a cup, but they do have an inside and an outside. The outside of the product is formed by the cavity, the inside by the core. The alternative to the cup shape is the flat shape. In this case, there is no specific convex portion, and sometimes, the core looks like a mirror image of the cavity. Typical examples
for this are plastic knives, game chips, or round disks such as records. While these items are simple in appearance, they often present serious molding problems for ejection of the product. Usually, the cavities are paced in the mold half that is mounted on the injection side, while the cores are placed in the moving half of the mold. The reason for this is that all injection molding machines provide an ejection mechanism on the moving platen and the products tend to shrink onto and cling to the core, from where they are then ejected. Most injection molding machines do not provide ejection mechanisms on the injection (“hot”) side.
2.3 INJECTION MOLDING
Many different processes are used to transform plastic granules, powders, and liquids into final product the plastic material is in moldable form, and is adaptable t various forming methods. In most cases thermoplastic materials are suitable for certain processes while thermosetting materials require other methods of forming. This is recognized by the fact that thermoplastics are usually heated to a soft state and then reshaped before cooling. Theromosets, on the other hand have not yet been polymerized before processing, and the chemical reaction takes place during the process, usually through heat, a catalyst, or pressure. It is important to remember this concept while studying the plastics manufacturing processes and the polymers used.
Injection molding is by far the most widely used process of forming thermoplastic materials. It is also one of the oldest. Currently injection molding accounts for 30% of all plastics resin consumption. Since raw material can be converted by a single procedure, injection molding is suitable for mass production of plastics articles and automated one-step production of complex geometries. In most cases, finishing is not necessary. Typical products include toy, automotive parts, household articles, and consumer electronics goods.
Since injection molding has a number of interdependent variables, it is a process of considerable complexity. The success of the injection molding
operation is dependent not only in the proper setup of the machine variables, but also on eliminating shot-to-shot variations that are caused by the machine hydraulics, barrel temperature variations, and changes in material viscosity. Increasing shot-to-shot repeatability of machine variables helps produce parts with tighter tolerance, lowers the levels of rejects, and increases product quality (e. g. appearance and serviceability).
The principal objective of any molding operation is the manufacture of products: to a specific quality level, in the shortest time, and using a repeatable and fully automatic cycle. Molders strive to reduce or eliminate rejected parts in molding production. For injection molding of high precision optical parts, or parts with a high added value such as appliance cases, the payoff of reduced rejects is high.
A typical injection molding cycle or sequence consists of five phases.
①Injection or mold filling
②Packing or compression
③Holding
④Coolin g
⑤Part ejection
Plastic granules are fed into the hopper and through an opening in the injection cylinder where they are carried forward by the rotating screw. The rotation of the screw forces the granules under high pressure against the heated walls of the cylinder causing them to melt. As the pressure builds up, the rotating screw is forced backward until enough plastic has accumulated to make the shot. The injection ram (or screw) forces molten plastic from the barrel, through the nozzle, sprue and runner system, and finally into the mold cavities, it solidifies (freezes) rapidly to produce the skin layer. Since the core remains in the molten state, plastic flows through the core to complete mold filling. Typically, the cavity is filled to 95%-98% during injection. Then the molding
process is switched over to the packing phase.
Even as the cavity is filled, the molten plastic begins to cool. Since the cooling plastic contracts or shrinks, it gives rise to defects such as sink marks, voids, and dimensional instabilities. To compensate for shrinkage, addition plastic is forced into the cavity. Once the cavity is packed, pressure applied to the melt prevents molten plastic inside the cavity from back flowing out through the gate. The pressure must be applied until the gate solidifies. The process can be divided into two steps (packing and holding ) or may be encompassed in one step (holding or second stage). During packing, melt forced into the cavity by the packing pressure compensates for shrinkage. With holding, the pressure merely prevents back flow of the polymer melt.
After the holding stage is completed, the cooling phase starts. During cooling, the part is held in the mold for specified period. The duration of the cooling phase depends primarily on the material properties and the part thickness. Typically, the part temperature must cool below the material’s ejection temperature. While cooling the part, the machine plasticates melt for the next cycle. The polymer is subjected to shearing action as well as the condition of the energy from the heater bands. Once the shot is made, plastication ceases. This should occur immediately before the end of the cooling phase. Then the mold opens and the part is ejected.
注塑模具简介
模具型腔可赋予制品形状，因此在塑料加工过程中模具处于非常重要的地位，这使得模具对于产品最终质量的影响与塑化机构和其他成型设备的部件一样关键，有时甚至更重要。

1.1 模具零部件
注塑成型模具由两部分组成，即定模和动模。

定模固定在定模板上，成型时直接与注塑机喷嘴接触；动模固定在动模板上，顶出机构通常设置在动模上。

模具的设计形式多样，包括复杂制件的组合式模具，在成型设备上一次生产多个之间的多型腔模具。

平衡式浇注系统可将塑料自注道通过浇口注入各个型腔，浇口是限制性、尺寸小于流道的通道，可保证熔体平稳填充到型腔，并且容易将制品从浇注系统上分开。

大多数注塑模具都可以将制品从浇道凝料上分开而不需其他的切除工序，通常可通过观察制品上的浇口去除去部位来判断其为注塑成型制件，浇口通常设在塑件的边缘或合模线处及圆形制品的中心位置。

模具和成型机械一样都很贵，但当制品设计完毕，模具制造完后开始投入生产，制品可以低成本大批量生产。

实际上所有热塑性塑料都可以通过适当的模具和设备进行注射成型。

可大批量生产的具有标准形状和尺寸的模具部件叫标准件，依据详细的模具零件图纸采用铣削、车削、电火花、磨削等方法分别加工出这些模具零件，最后，模具制造人员将这些零件和标准模架以及其他金属件进行装配。

如今，已经有很多厂商生产经营模具标准件。

1.2 热流道系统
热流道系统根据其加热形式不同可分为：绝热流道系统和真正意义上的热流道系统。

后者又可分为一下两种形式：内部加热和外部加热。

加热可通过筒式加热器、加热棒、加热圈、加热管和加热线圈等完成，为保证熔体的流动和分布均匀，需要用到带有若干加热回路和一定数量的传感器得相对精确的控制系统，工作电压一般为220-240V，但小型喷嘴常用低至5V的电压，有时也用15V和24V的电压。

传统模具中浇注系统的温度一般与模具其他部分温度相同，因为它们处于同一模块中，但是，如果浇注系统设置在特定的集流板中并加热到熔体温度时，就会有一下一些优点：加热到熔体温度的热流道可以将熔体均匀分配到各个浇口。

热流道模具可用于所有热塑性材料及交联塑料如弹性体和热固性材料的模塑成型。

对于热塑性材料，这些集流腔通常是指热流道系统、热器官或者简单称之为热流道。

对于交联材料被称为冷流道。

A.热流道系统
热流道系统主要是针对生产大批量、自动化程度高的热塑性制品而设计。

使用这种形式也主要是出于经济考虑，即产量较大时用。

至于从产品
质量的角度考虑，以往是很重视的，现在却很少考虑这个因素，因为热塑性塑料用热流道成型的技术已经非常成熟，用得也越来越多。

已有热流道系统的标准件生产，单独生产很不合算，相应的供应商不仅提供配件甚至可为专门的需求提供整套系统，可供选择的单个配件也很多。

B.热流道系统的经济优、劣势
1.经济优势
节约材料和回收成本
缩短成型周期，冷却时间可不再由缓慢的流道冷却时间决定，喷嘴不用后退；由于减少了注射量（减少了流道中的料），所需设备规格可减少，由于流道歧管闭合，流道不会产生力，故锁模力可以降低。

经济劣势
设备更复杂和昂贵；
首次驱动模具工作时需耗费更多精力；
成型进程容易中断，维护费高（泄露、加热元件易出故障、填充材料造成的磨损等）；
2.技术优势
成型可自动化（脱模），由于不需再脱除浇道；
浇口的布置可最合理，因为浇口部分的一致性、冷却控制更精确，允许流道很长；
压力损失降到最小，由于流道直径不再受限制；
浇注系统可人工平衡，可通过成型时控制温度或机械调节（调整环状口模或在流道设置版状物）实现（自然平衡最好）；
采用针阀式喷嘴及有选择地对其调节还衍生了一些新技术（阶式浇口系统、消除了留痕、实现模内装饰）；
相对于传统地三板模，开模行程小；
保压压力作用时间更长，从而减少翘曲变形。

3.技术劣势
由于流道和物料停留时间，尤其是对于成型周期长的情况，对热敏性材料不利；
温度控制的不均匀可能会导致熔体温度差异和非均匀充填，因此需要较精确的温度控制。

C.热流道系统及其元件的设计
热流道模具从技术角度看更有优势，因为在不对材料造成危害的前提下，能利用更高级的技术经济有效地将熔体输送到浇口。

D.内/外加热系统
两种形式的优缺点可以显而易见的看出来。

E.外部加热系统
1.优点
流道较大使得流动速率低、温度分布更均匀。

2.缺点
外部加热的热量会非常高，比如尼龙66的模温大约要100摄氏度，歧管温度至少要270摄氏度，这就意味着模板中存在着至少170摄氏度的温差，结果是：
需要有特殊手段将热流道喷嘴与浇口固定在一起，因为有相对大的热传递；
上述问题解决不好容易中断成型过程；
更高的加热功率（40.7 mm2截面时每100mm长度需要超过500W的功率）；
模块的绝热；
模具表面积很大，如果模板固定板设计的不够厚，较大的无支撑区域会造成进料侧的固定板弯曲，模具也很很重。

F.内部加热系统
在流道内壁形成的冻结塑料层会起到绝热层的作用。

系统所需热量较低（内部管道每100mm大约需要55W的功率）；
模具和歧管块之间的温度差可以忽略，较高热传递所要的一些措施都不再必须；
内部加热系统的歧管可以做成紧凑的模块并与模具紧紧地铆接在一起，因此模具非常坚固，喷嘴和浇口不需要对中，注塑机一侧的模板可以加工为一体，由固定的模具和内嵌式歧管组成。

熔体体积较小，流动熔体的停留时间较短，另外流动速度非常大会危机塑料材料，建议不要将内部加热系统用于热敏性材料。

当选定某一加热系统后，可以从供应商处得到技术支持。

2.1 注塑模
A.模具设计基础
注塑模至少由两个半模组成，分别固定在注塑机的两个模板上，以保证能顺利开合模。

模具闭合时，塑料熔体通过浇注系统和浇口注入由两个半模围成的型腔，型腔决定了制品的外表面形状，冷却系统保证制品冷却固化，以便随后被顶出。

B.顶出形式
要顶出制品，就必须得开模，制品形状决定了它是能被直接开模取出还是必须考虑到凹孔的影响。

决定模具设计的因素主要有成型制品的形状和顶出机构的形式。

注塑制品可被归为一下几类：
1.不带凹孔的制品，如板状物、条状、半壳体、杯状物等；
2.外部带凹孔或侧孔的制品，如线轴、绕线圈、饮料箱、螺栓
等；
3.内部带凹孔的制品，如螺纹罩、壳等；
4.外部和内部均带凹孔的制品，如减震器盘、电子和汽车仪表
壳、相机等。

C.不带凹孔的制品
不带凹孔制品的磨具图，制品由点浇口在3处进料成型，一个模塑周期完成后在4处开模，左半模后退，制品留在型芯5上，模板7上的凹槽将主流道凝料6从浇口套8内拉出，模具继续开启，顶出杆10由机械式顶出机构带动工作，推板11停止运动，这时带着模塑制品的左半模继续左移，安在推板11上的顶杆1顶动附在型芯5上的制品。

同时，推杆9将主道凝料6自模板7上的凹孔顶出，，主道凝料和制品一起被顶开，模具闭合时，回程杆2将带有顶出杆1的卸料板11带回到起始位置。

D.外部带凹孔的制品
外部带凹孔的厨房用具外壳的脱模情况，斜导柱24安装在定模一侧，并插入滑块23的斜孔内，滑块由动模侧的两个镶板作导向。

模具闭合时，滑块23由楔紧块26固定，这样斜导柱24在注射时不会受力，当模具开启时，斜导柱24推动滑块23运动直到将制品上的凹孔卸除，当斜导柱完全从滑块上的倒孔上拉出来时，弹簧控制的球式棘爪2保证滑块23不移动，制品留在动模侧，随后被顶出杆4和顶管9顶出，模具闭合，顶出机构和滑块23分别由回程杆12和斜导柱24拖动回到初始位置。

E.内部带凹孔的制品
如果制品内部有侧向凹孔，在脱离型芯时会发生干涉影响脱模
强制脱模
如果凹槽不是太深并且模塑材料有足够的弹性，就可能将制品自型芯上强行脱出。

以生产聚乙烯盖状制品的模具图为例说明一下，这类制品大约呈卵形，内部有突出的边缘，从而在整个制品内部形成一圈凹槽，由于聚乙烯弹性较大，就省去了复杂得顶出机构。

注射完成后，模具在I处开启，制品随同型芯一起自型腔46中脱出，当脱模顶杆14动作时，推板7带动脱模板拉杆33、脱模板3前移，脱模板上镶有脱模圈49（合模线II处），同时带有型芯47、48的推板8在压缩弹簧39的作用下前移。

模板4通过垫块固定在动模底板5上不动，成型环镶嵌在模板4上也保持不动，这样，制品和型芯从成型环50上脱出。

运动距离W后，模板8碰到模板4，型芯47、48停止运动；弹簧39被压缩，脱模圈继续前移，将制品自型芯上脱出。

在脱模过程中，脱模圈49作用在制品边缘使其变形张大。

为了保证制品边缘能够变形张大，脱模圈不应将制品边缘攥的太紧。

2.2 注塑模具设计
A.设计原则
模具设计的原则很多，这些原则都是基于逻辑、以往经验、加工的方便性和经济性考虑，在设计、模具制造和模具模塑成型过程中遵守这些规则是很有用的。

但有时，忽略某一原则而遵循另一原则往往会更好些。

本文将介绍最常用的设计原则，但设计人员只有从实践经验中才能有所收获。

设计者应随时关注与这些设计原则有关的新观点、模塑方法、材料。

B.磨具基础
1.模腔
模腔指的是通过机加工在模具材料内部切挖出的空间，以供模塑材料，即塑料填充，并获取该空间形状得到需要的制品。

模具的历史几乎与人类文明一样悠久，通过在沙型这类的模具中注入液体金属如铁、青铜，生产出工具，为了取出固化后的制品，需要将模具打碎，因此这种模具只能使用一次。

我们一直在寻求可以反复使用的永久性模具，现在可以用坚固耐用的材料如钢材、软质吕及其他合金材料生产模具，当生产量不是很大、模具寿命要求不是很高时，甚至可用某些塑料制造模具。

注塑生产时，熔料以高压注入型腔，因此就需要模具足够结实以抵御变形。

2.型腔数量
多数模具，尤其生产大型制品的模具多为单腔模，但大批量生产时的模具，会有两个或更多个型腔，这纯粹是处于经济考虑。

注射多型腔的时间并步比单型腔模多，例如四腔模注射一个产品的时间大约仅是单腔模的1/4，而产量却与型腔数成正比。

多腔模比单腔模贵，并不是说要贵四倍，但需要带有大模板和锁紧能力的注塑机，而且该例所需总的塑料量是单腔模的四倍，需要有较大的住宿装置，较大设备的单位成本要比用小型模具的设备高。

目前多型腔模大多选择2、4、6、8、12、16、
24、32、48、64、96、128这样的数字。

选择这些数字（偶数）的原因是为了方便在长方形区域内布置型腔，这样有利于设计、定尺寸以方便加工制造，也有利于围绕机器中心对称布置型腔，这种对称分布对保证每个型腔分配到相同的锁模力非常重要。

也可以在圆形范围内设置较少量的型腔数，甚至于是3，5，7，9这样的奇数，还可用任意型腔数排布，但要注意围绕注塑机中心线投影面积对称分布。

3.型腔形状及收缩率
型腔形状实际上时塑件形状的“反”形状。

尺寸需要加上塑料的收缩量。

型腔形状可以用切削设备或电火花、化学腐蚀及任何新型加工方。