unit6 注塑成型

1、机械工程专业英语北华大学机械工程学院王开宝Unit 6nInjection molding (Fig.6.1) is the predominant process for fabrication of thermoplastics into finished forms, and is increasingly being used for thermosetting plastics, fiber-filled composites, and elastomers.n注塑成型(图6.1)是将热塑性塑料制成最终形状的主要工艺，并且越来越多地用于热硬化性塑料、纤维填充合成物和人造橡胶。n It

2、 is the process of choice for tremendous variety of parts ranging in weight from 5g to 85kg. It is estimated that 25% of all thermoplastics are injection molded. n它是重量范围为5g到85kg极大一类零件可选用的工艺。估计所有热塑性塑料中有25%是采用注塑成型的。nIf newer modifications, such as reaction injection molding, and the greatly increased

3、rate of adoption of plastics as substitutes for metals are considered, it is likely that the worldwide industrial importance of injection molding will continue to increase.n 如果考虑到新近的改进(例如反作用注塑成型)和采用塑料替代金属的高增长率，注塑成型在世界范围的工业重要性很可能将继续增加。nCurrently, probably close to half of all major processing units i

4、s injection molding machines. In 1988, a dollar sale of new injection molding machinery in the U.S. was approximately 65% of total major polymer machinery sales volume; this included 4,600 injection molding units. n当前，大概所有主要处理设备的近一半是注塑成型机。1988年，美国新的注塑成型机械销售约占全部主要聚合物机械销售量的65%，其中包括4,600台注塑成型设备。nThe ma

5、chines and their products are ubiquitous and are synonymous with plastics for many people.n这类机械和它们的产品普遍存在，对许多人来说与塑料是同义的。n A reciprocating screw injection molding machine combines the functions of an extruder and a compressive molding press.n 往复螺旋注射成型机把压出机和成型压力机的功能结合起来。nIt takes solid granules of the

6、rmoplastic resin, melts and pressurizes them in the extruder section, forces the melt at high velocity and pressure through carefully designed flow channels into a cooled mold, then ejects the finished part(s), and automatically recycles. n把热塑性塑料树脂的固体颗粒在压出部分融化并增压，迫使其高速融化并通过仔细设计的流动通道进入冷却模具，喷射成最终零件，然后

7、自动再循环。This machine is a descendant of the plunger type “stuffing machine” patented by the Hyatt brothers in 1872 to mold celluloid. In 1878, the Hyatts developed the first multicavity mold, but it was not until 1938 that Quillery (France) patented a machine incorporating a screw to plasticize the el

8、astomer being molded. 这种机械是1872年Hyatt兄弟获得专利权的融化赛璐珞的活塞型“填充机”的派生物。 1878年Hyatt兄弟开发了第一个多槽模具，但直到1938年Quillery(法国)才发明了用螺旋增塑人造橡胶并使其成型的一体化机械。nIn 1956, Ankerwerk Nuremberg commercialized the modern reciprocating screw injection molding machine for thermoplastics. Today, over 50 machine manufacturers are list

9、ed in Modern Plastics Encyclopedia, offering machines to the U.S. market ranging from 2 to 6,000 tons clamping capacity. n1956年，Ankerwerk Nuremberg使用于热塑性塑料的现代往复螺旋注塑成型机商业化。今天，已有超过50家制造商列入现代塑料制品百科全书，能为美国市场提供压制能力从2到6,000吨的机械。n(A machine with a 10,000-ton capacity has been built to mold 264-gallon HDPE

10、trash containers.) A host of suppliers of auxiliary equipment, molds, instruments, and controls service this major segment of the polymer industry.n(一台能力为10,000吨用于成型264加仑高密度聚乙烯垃圾箱的机械也已制成)。许多辅助设备、模具、仪器和控制系统供应商在为聚合物工业的这一主要部分服务。nInjection molding is particularly worthy of intensive study because it com

11、bines many areas of interest extrusion, mold design, rheology, sophisticated hydraulic and electronic controls, robotic accessories, design of complex products, and, of course, the integration of materials science and process engineering. n注塑成型对深入研究很有价值，因为它结合了许多重要领域，如挤压、模具设计、流变学、完备的液压和电子控制、机器人配件、复杂产

12、品的设计，当然还有材料科学与加工工程的综合。nThe objectives of injection molding engineers are simple enough: to obtain minimum cycle time with minimum scrap, to attain specified product performance with assurance, to minimize production costs due to downtime or any other reasons, and to steadily increase in expertise an

13、d competitiveness.n注塑成型工程师的目标很简单：在最少废料的情况下取得最小循环时间，在有保证的情况下获得指定产品性能，将由停工或其它原因产生的生产成本最小化，还有稳定地增加专门知识和竞争力。nProfit margins for custom injection molders are said to be generally skimpy; an established way to improve profits is to be selected for more demanding, higher margin jobs that demand the highest

14、 level of efficiency and competence.n传统的注塑成型机利润盈余据说一般是不足的；为了更多需求及更高盈余工作需要选择一种改善利润的确定方法，它要求最高水平的效率和能力。n This text will concentrate on the reciprocating screw machine for thermoplastics, which has largely replaced the older reciprocating plunger types except for very small-capacity machines.n本文将集中论述热塑

15、性塑料用的往复螺旋机，除了小容量机械外它已在很大程度上取代了较老的往复活塞式机械。Injection Molding Materials注塑成型材料nIt is not possible to injection-mold all polymers. Some polymers like PTFE (Poly-tetra-fluoro-ethylene), cannot be made to flow freely enough to make them suitable for injection molding.n要注塑成型所有聚合物是不可能的。像聚四氟乙烯之类的聚合物就不能自由流动得足以

16、适合注塑成型。nOther polymers, such as a mixture of resin and glass fiber in woven or mat form, are unsuitable by their physical nature for use in the process. In general, polymers which are capable of being brought to a state of fluidity can be injection-molded.n其它聚合物，例如树脂和编织的或垫子形的玻璃纤维的混合物，由于它们的物理性质不适合使用此

17、工艺。一般而言，能进入流动状态的聚合物都可以注塑成型。nThe vast majority of injection molding is applied to thermoplastic polymers. This class of materials consists of polymers which always remain capable of being softened by heat and of hardening on cooling, even after repeated cycling. n注塑成型的绝大多数都用于热塑性聚合物。这类材料由具有加热软化、冷却硬化甚至

18、可重复循环能力的聚合物组成。nThis is because the long-chain molecules of the material always remain as separate entities and do not form chemical bonds to one another. An analogy car, be made to a block of ice that can be softened (i.e. turned back to liquid), poured into any shape cavity, and then cooled to beco

19、me a solid again. n这是由于这类材料的长链分子总是保持分离的实体并不相互形成化学连结。一辆由冰块制成的模拟汽车，可以融化(即转化为液态)，倒入任何形状的空腔，然后冷却重新变成固体。nThis property differentiates thermoplastic materials from thermosetting ones. In the latter type of polymer, chemical bonds are formed between the separate molecule chains during processing. In this c

20、ase the chemical bonding referred to as cross linking is the hardening mechanism.n这个特性将热塑性材料与热硬化性材料区分开。后者在加工过程中分离的分子链之间形成化学连结。在此情况下作为交联的化学连结是硬化机制。nIn general, most of the thermoplastic materials offer high impact strength, corrosion resistance, and easy processing with good flow characteristics for

21、molding complex designs. Thermoplastics are generally divided into two classes: namely crystalline and amorphous. n一般而言，大多数热塑性材料具有较高的抗冲击强度、耐腐蚀性以及良好流动性使其容易加工而适于复杂成型设计。热塑性塑料通常分为两类：即结晶质的和非结晶质的。nCrystalline polymers have an ordered molecular arrangement, with a sharp melting point. Due to the ordered ar

22、rangement at molecules, the crystalline polymers reflect most incidents light and generally appear opaque. n结晶质聚合物具有规则的分子排列及明显的熔点。由于规则的分子排列，结晶质聚合物能反射大多数特定光线并一般表现为不透明的。nThey also undergo a high shrinkage or reduction in volume during solidification. Crystalline polymers usually are more resistant to

23、organic solvents and have good fatigue and wear-resistant properties. Crystalline polymers also generally are denser and have better mechanical properties than amorphous polymers. n它们在固化过程中收缩较大或体积减少较多。结晶质聚合物通常多能抵御有机溶剂并具有良好的抗疲劳和磨损特性。结晶质聚合物通常也比非结晶质聚合物更致密并且具有更好的机械性能。nThe main exception to this rule is

24、polycarbonate, which is the amorphous polymer of choice for high quality transparent moldings, and has excellent mechanical properties.n其中主要例外是聚碳酸酯，它是可选用做高质量透明注塑件的非结晶质聚合物，并具有卓越的机械性能。n The mechanical properties of thermoplastics, while substantially lower than those of metals, can be enhanced for som

25、e applications through the addition of glass fiber reinforcement. This takes the form of short-chopped fibers, a few millimeters in length, which are randomly mixed with the thermoplastic resin.n就本质而言，热塑性塑料的机械性能低于金属，但可以通过加入玻璃纤维强化予以增强来适应某些运用。常用几毫米长的短碎纤维随机地与热塑性树脂混合。nThe fibers can occupy up to one thi

26、rd of the material volume to considerably improve the material strength and stiffness. The negative effect of this reinforcement is usually a decrease in impact strength and an increase in abrasiveness. n纤维可占材料体积的三分之一以极大改善材料的强度和硬度。这种加强的负作用通常是抗冲击强度降低及磨损性增加。nThe latter also has an effect on processing

27、 since the life of the mold cavity is typically reduced from about 1,000,000 parts for plain resin parts to about 300,000 for glass-filled parts.n后者对加工过程也有影响，因为模具腔的寿命从典型的普通树脂零件大约1,000,000件减少到玻璃纤维填充树脂零件的约300,000件。nPerhaps the main weakness of injection-molded parts is the relatively low service tempe

28、ratures to which they can be subjected. Thermoplastic components can only rarely be operated continuously above 250, with an absolute upper service temperature of about 400. n注塑成型零件的主要缺点或许是它们能承受的工作温度相对较低。热塑性塑料零件只有很少能连续运行在250以上，其绝对最高工作温度约为400。nThe temperature at which a thermoplastic can be operated

29、under load can be defined qualitatively by the heat deflection temperature. This is the temperature at which a simply supported beam specimen of the material, with a centrally applied load, reaches a predefined deflection.n热塑性塑料带载运行温度可从质量上定义为热偏差温度。这是中心承载的该材料简支梁达到预定偏差的温度。nThe temperature value obviou

30、sly depends upon the conditions of the test and the allowed deflection and for this reason, the test values are only really useful for comparing different polymers.n其温度值明显取决于试验条件和允许偏差，因此对比较不同的聚合物而言只有试验数据是真正有用的。Cycle of Operation作业循环nThe reciprocating screw injection molding machine is considered as

31、consisting of two halves: a fixed injection side, and a movable clamp side.n 往复螺旋注塑成型机被认为由两部分组成：一个固定注塑端和一个活动夹具端。nThe injection side contains the extruder that receives solid resin in pellet or granular form and converts it into a viscous liquid or melt that can be forced through the connecting nozzl

32、e, spine, and runners to the gates that lead into the mold cavities. n注塑端包含压出机，它接受小球或粒状的固体树脂，然后将其转化为粘性液体或称为融化，再强迫其通过连接喷嘴、中心和浇道到闸道进入模具腔。nThe mold is tightly clamped against injection pressure and is cooled well below the melt temperature of the thermoplastic. When the parts in the cavities have coole

33、d sufficiently the mold halves are opened at the mold parting plane and the parts ejected by a knockout system drop into a receiving bin below. n模具被紧紧地夹住以抵抗注塑压力，并在热塑性塑料的融化温度以下很好地冷却。当模腔内的零件充分冷却，剖分模在模具分模面处打开，推出系统将零件推出落入下面的接收容器内。nThis summarizes the overall cycle, but leaves out much vital detail that

34、is necessary for understanding the process. However, with this introduction, it is possible to understand the advantages and disadvantages of the process.n这概述了整个循环，但省略了许多对理解此工艺所必需的很重要细节。然而通过本介绍，了解这种工艺的优缺点仍是可能的。Effects of Process Variables on Orientation 加工变量对方向性的影响nIn injection molding, any variatio

35、n in processing that keeps the molding resin hot throughout filling allows increased relaxation and, therefore, decreased orientation. Some of the steps that can be taken to reduce orientation are as follows.n在注塑成型时，整个填料过程始终保持成型树脂高温的任何加工变化都会增加松弛作用而减少方向性。下面是可以用于减少方向性的若干措施。nFaster injection (up to a p

36、oint): less cooling during filling, hence a thinner initial frozen layer, lower viscosity due to shear thinning; better flow to corners; and less crystallinity all favor lower subsurface orientation. The primary effect is that the gate will freeze more quickly. At that point, orientation stops and r

37、elaxation starts.n较快注塑(到点)：在填料过程中冷却较少，因此初始固化层较薄，由于剪应变稀少而粘性较低；能较好地流到角落；结晶度较小；所有这些促成表面下的方向性也较低。主要效果是闸道将较快固化。这样使得方向性停止产生而松弛作用开始增加。nHigher melt and mold temperatures: lower melt viscosity, easier filling, and greater relaxation favor reduced orientation.nReduced packing time and pressure: overpacking in

38、hibits relaxation processes.n较高的融化和成型温度：融化粘性较低，更容易填充，较大松弛作用促成方向性减少。n减少挤压时间和压力：过度挤压会抑制松弛过程。nReduced gate size: larger gates take longer to freeze off and permit increased orientation.n减小闸道尺寸：闸道越大则固化时间越长并会使方向性增加。n Excessively high injection speed can cause high surface orientation and increase suscept

39、ibility to stress cracking. For example, moldings that are to be electroplated, and will be subject to acid solutions during plating, must be made using very slow injection speeds to minimize surface orientation. n过高的注塑速度会引起较高的表面方向性及增加应力破裂的敏感性。例如，要电镀的注塑件在电镀时会经受酸溶液，必须采用很低的注塑速度制造以使表面方向性最小化。nOn the oth

40、er hand, the transverse motion component of the melt front in most moldings can cause transverse subsurface orientation superimposed on the primary orientation, giving a desirable biaxial orientation effect.n另一方面，大多数注塑件的融化前部横向运动部分能导致在主要方向性上有层理的表面下横向方向性，产生需要的双轴方向性效应。nOrientation can be seriously incr

41、eased by obstructions to flow during filling of the cavity. Flow around an obstruction causes a decrease in melt front speed and leads to high local viscosity and reduced relaxation. This is also likely to occur near the end of the filling phase if gating is inadequate.n 在填充模腔时流动受到阻碍会极大地增加方向性。围绕障碍物流

42、动使融化前部的速度下降并产生较高的局部粘性而减少松弛作用。如果闸道不适当，这也很可能发生在接近填充结束阶段。n The molder must recognize the dangers of excessive fill speed, insufficient injection pressure, excessive melt temperature, and inadequate packing. These dangers are weighed against the opposing effects on orientation discussed above.n注塑工必须认识过快

43、填充速度、不足注塑压力、过高融化温度和不充分挤压的危害性。这些危害性要与上述方向性的反向效应相权衡。nThicker parts delay cooling and increase relaxation time and tend to result in lower orientation. Thicker parts also tend to warp less. Therefore, a minimum wall thickness can be established by experience for various shapes, materials, and process c

44、ombinations. n较厚零件会延迟冷却并且增加松弛时间，趋向于导致较低的方向性。较厚零件也有助于减少翘曲。因此，对各种形状、材料和工艺组合能通过经验来确定最小壁厚。nLower molecular weight and broader molecular weight distribution in thermoplastics favor lower orientation and reduced internal stress in moldings.n在热塑性塑料中较小的分子量以及较宽泛的分子量分布促成方向性减少同时降低注塑件中的内应力。nThe skin thickness r

45、atio is affected by process variables in the same way as one would predict for the orientation; that is, it decreases as the melt or mold temperatures and cavity pressure increases. Tensile strength and stiffness increase as skin thickness ratio increases. Microscopic examination thus provides anoth

46、er way of studying the process efficiently.n外壳厚度比受加工变量影响的方式与方向性预测一样；也就是它能随融化或成型温度及模腔压力的增加而减少。拉伸强度和硬度随外壳厚度比增加而增加。因而显微镜检查提供了有效研究该工艺的另一方法。Advantages 优点1. High production rates. For example, a CD disk can be produced with a 1012s cycle in high melt flow index PC.1. 高生产率：例如，一张CD盘在高融体流动指数生产控制中只需1012s一个循环就

47、能生产出来。 2. Relatively low labor content. One operator can frequently take care of two or more machines, particularly the moldings are unloaded automatically onto conveyors. 2. 相对较少的工作内容：一个操作者经常可以照看两台以上机械，尤其是当成品能自动卸到输送机上时。3. Parts require little or no finishing. For example, flash can be minimized and

48、 molds can be arranged to automatically separate runners and gates from the part itself.3. 零件几乎不需要修整：例如，飞边可以最小化并且模具能被设计成自动将浇道和闸道从零件本身分离。4. Very complex shapes can be formed. Advances in mold tooling are largely responsible.4. 非常复杂的形状也能成型：模具的进步很大程度上是可靠的。 5. Flexibility of design (finishes, colors, in

49、serts, materials). More than one material can be molded through co-injection. Foam core materials with solid skins are efficiently produced. Thermosetting plastics and fiber-reinforced shapes are injection molded. 5. 设计的灵活性(光洁度、颜色、插入物、材料)：通过复合注塑可以成型多于一种材料。可以高效地生产带有固体外壳的泡沫型芯材料。热硬化性塑料和纤维加强形状都可以注塑成型。 6. Minimum scrap loss. Runner