1、機(jī)械工程專業(yè)英語北華大學(xué)機(jī)械工程學(xué)院王開寶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(圖6.1)是將熱塑性塑料制成最終形狀的主要工藝，并且越來越多地用于熱硬化性塑料、纖維填充合成物和人造橡膠。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它是重量范圍為5g到85kg極大一類零件可選用的工藝。估計(jì)所有熱塑性塑料中有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 如果考慮到新近的改進(jìn)(例如反作用注塑成型)和采用塑料替代金屬的高增長率，注塑成型在世界范圍的工業(yè)重要性很可能將繼續(xù)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當(dāng)前，大概所有主要處理設(shè)備的近一半是注塑成型機(jī)。1988年，美國新的注塑成型機(jī)械銷售約占全部主要聚合物機(jī)械銷售量的65%，其中包括4,600臺(tái)注塑成型設(shè)備。nThe ma

5、chines and their products are ubiquitous and are synonymous with plastics for many people.n這類機(jī)械和它們的產(chǎn)品普遍存在，對(duì)許多人來說與塑料是同義的。n A reciprocating screw injection molding machine combines the functions of an extruder and a compressive molding press.n 往復(fù)螺旋注射成型機(jī)把壓出機(jī)和成型壓力機(jī)的功能結(jié)合起來。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把熱塑性塑料樹脂的固體顆粒在壓出部分融化并增壓，迫使其高速融化并通過仔細(xì)設(shè)計(jì)的流動(dòng)通道進(jìn)入冷卻模具，噴射成最終零件，然后

7、自動(dòng)再循環(huán)。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. 這種機(jī)械是1872年Hyatt兄弟獲得專利權(quán)的融化賽璐珞的活塞型“填充機(jī)”的派生物。 1878年Hyatt兄弟開發(fā)了第一個(gè)多槽模具，但直到1938年Quillery(法國)才發(fā)明了用螺旋增塑人造橡膠并使其成型的一體化機(jī)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使用于熱塑性塑料的現(xiàn)代往復(fù)螺旋注塑成型機(jī)商業(yè)化。今天，已有超過50家制造商列入現(xiàn)代塑料制品百科全書，能為美國市場(chǎng)提供壓制能力從2到6,000噸的機(jī)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(一臺(tái)能力為10,000噸用于成型264加侖高密度聚乙烯垃圾箱的機(jī)械也已制成)。許多輔助設(shè)備、模具、儀器和控制系統(tǒng)供應(yīng)商在為聚合物工業(yè)的這一主要部分服務(wù)。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注塑成型對(duì)深入研究很有價(jià)值，因?yàn)樗Y(jié)合了許多重要領(lǐng)域，如擠壓、模具設(shè)計(jì)、流變學(xué)、完備的液壓和電子控制、機(jī)器人配件、復(fù)雜產(chǎn)

12、品的設(shè)計(jì)，當(dāng)然還有材料科學(xué)與加工工程的綜合。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注塑成型工程師的目標(biāo)很簡單：在最少廢料的情況下取得最小循環(huán)時(shí)間，在有保證的情況下獲得指定產(chǎn)品性能，將由停工或其它原因產(chǎn)生的生產(chǎn)成本最小化，還有穩(wěn)定地增加專門知識(shí)和競(jìng)爭(zhēng)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傳統(tǒng)的注塑成型機(jī)利潤盈余據(jù)說一般是不足的；為了更多需求及更高盈余工作需要選擇一種改善利潤的確定方法，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本文將集中論述熱塑

15、性塑料用的往復(fù)螺旋機(jī)，除了小容量機(jī)械外它已在很大程度上取代了較老的往復(fù)活塞式機(jī)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。像聚四氟乙烯之類的聚合物就不能自由流動(dòng)得足以

16、適合注塑成型。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，例如樹脂和編織的或墊子形的玻璃纖維的混合物，由于它們的物理性質(zhì)不適合使用此

17、工藝。一般而言，能進(jìn)入流動(dòng)狀態(tài)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注塑成型的絕大多數(shù)都用于熱塑性聚合物。這類材料由具有加熱軟化、冷卻硬化甚至

18、可重復(fù)循環(huán)能力的聚合物組成。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這是由于這類材料的長鏈分子總是保持分離的實(shí)體并不相互形成化學(xué)連結(jié)。一輛由冰塊制成的模擬汽車，可以融化(即轉(zhuǎn)化為液態(tài))，倒入任何形狀的空腔，然后冷卻重新變成固體。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這個(gè)特性將熱塑性材料與熱硬化性材料區(qū)分開。后者在加工過程中分離的分子鏈之間形成化學(xué)連結(jié)。在此情況下作為交聯(lián)的化學(xué)連結(jié)是硬化機(jī)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，大多數(shù)熱塑性材料具有較高的抗沖擊強(qiáng)度、耐腐蝕性以及良好流動(dòng)性使其容易加工而適于復(fù)雜成型設(shè)計(jì)。熱塑性塑料通常分為兩類：即結(jié)晶質(zhì)的和非結(jié)晶質(zhì)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結(jié)晶質(zhì)聚合物具有規(guī)則的分子排列及明顯的熔點(diǎn)。由于規(guī)則的分子排列，結(jié)晶質(zhì)聚合物能反射大多數(shù)特定光線并一般表現(xiàn)為不透明的。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它們?cè)诠袒^程中收縮較大或體積減少較多。結(jié)晶質(zhì)聚合物通常多能抵御有機(jī)溶劑并具有良好的抗疲勞和磨損特性。結(jié)晶質(zhì)聚合物通常也比非結(jié)晶質(zhì)聚合物更致密并且具有更好的機(jī)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，它是可選用做高質(zhì)量透明注塑件的非結(jié)晶質(zhì)聚合物，并具有卓越的機(jī)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就本質(zhì)而言，熱塑性塑料的機(jī)械性能低于金屬，但可以通過加入玻璃纖維強(qiáng)化予以增強(qiáng)來適應(yīng)某些運(yùn)用。常用幾毫米長的短碎纖維隨機(jī)地與熱塑性樹脂混合。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纖維可占材料體積的三分之一以極大改善材料的強(qiáng)度和硬度。這種加強(qiáng)的負(fù)作用通常是抗沖擊強(qiáng)度降低及磨損性增加。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后者對(duì)加工過程也有影響，因?yàn)槟＞咔坏膲勖鼜牡湫偷钠胀渲慵蠹s1,000,000件減少到玻璃纖維填充樹脂零件的約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點(diǎn)或許是它們能承受的工作溫度相對(duì)較低。熱塑性塑料零件只有很少能連續(xù)運(yùn)行在250以上，其絕對(duì)最高工作溫度約為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熱塑性塑料帶載運(yùn)行溫度可從質(zhì)量上定義為熱偏差溫度。這是中心承載的該材料簡支梁達(dá)到預(yù)定偏差的溫度。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其溫度值明顯取決于試驗(yàn)條件和允許偏差，因此對(duì)比較不同的聚合物而言只有試驗(yàn)數(shù)據(jù)是真正有用的。Cycle of Operation作業(yè)循環(huán)nThe reciprocating screw injection molding machine is considered as

31、consisting of two halves: a fixed injection side, and a movable clamp side.n 往復(fù)螺旋注塑成型機(jī)被認(rèn)為由兩部分組成：一個(gè)固定注塑端和一個(gè)活動(dòng)夾具端。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注塑端包含壓出機(jī)，它接受小球或粒狀的固體樹脂，然后將其轉(zhuǎn)化為粘性液體或稱為融化，再強(qiáng)迫其通過連接噴嘴、中心和澆道到閘道進(jìn)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模具被緊緊地夾住以抵抗注塑壓力，并在熱塑性塑料的融化溫度以下很好地冷卻。當(dāng)模腔內(nèi)的零件充分冷卻，剖分模在模具分模面處打開，推出系統(tǒng)將零件推出落入下面的接收容器內(nèi)。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這概述了整個(gè)循環(huán)，但省略了許多對(duì)理解此工藝所必需的很重要細(xì)節(jié)。然而通過本介紹，了解這種工藝的優(yōu)缺點(diǎn)仍是可能的。Effects of Process Variables on Orientation 加工變量對(duì)方向性的影響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在注塑成型時(shí)，整個(gè)填料過程始終保持成型樹脂高溫的任何加工變化都會(huì)增加松弛作用而減少方向性。下面是可以用于減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較快注塑(到點(diǎn))：在填料過程中冷卻較少，因此初始固化層較薄，由于剪應(yīng)變稀少而粘性較低；能較好地流到角落；結(jié)晶度較小；所有這些促成表面下的方向性也較低。主要效果是閘道將較快固化。這樣使得方向性停止產(chǎn)生而松弛作用開始增加。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較高的融化和成型溫度：融化粘性較低，更容易填充，較大松弛作用促成方向性減少。n減少擠壓時(shí)間和壓力：過度擠壓會(huì)抑制松弛過程。nReduced gate size: larger gates take longer to freeze off and permit increased orientation.n減小閘道尺寸：閘道越大則固化時(shí)間越長并會(huì)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過高的注塑速度會(huì)引起較高的表面方向性及增加應(yīng)力破裂的敏感性。例如，要電鍍的注塑件在電鍍時(shí)會(huì)經(jīng)受酸溶液，必須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，大多數(shù)注塑件的融化前部橫向運(yùn)動(dòng)部分能導(dǎo)致在主要方向性上有層理的表面下橫向方向性，產(chǎn)生需要的雙軸方向性效應(yīng)。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 在填充模腔時(shí)流動(dòng)受到阻礙會(huì)極大地增加方向性。圍繞障礙物流

42、動(dòng)使融化前部的速度下降并產(chǎn)生較高的局部粘性而減少松弛作用。如果閘道不適當(dāng)，這也很可能發(fā)生在接近填充結(jié)束階段。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注塑工必須認(rèn)識(shí)過快

43、填充速度、不足注塑壓力、過高融化溫度和不充分?jǐn)D壓的危害性。這些危害性要與上述方向性的反向效應(yīng)相權(quán)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較厚零件會(huì)延遲冷卻并且增加松弛時(shí)間，趨向于導(dǎo)致較低的方向性。較厚零件也有助于減少翹曲。因此，對(duì)各種形狀、材料和工藝組合能通過經(jīng)驗(yàn)來確定最小壁厚。nLower molecular weight and broader molecular weight distribution in thermoplastics favor lower orientation and reduced internal stress in moldings.n在熱塑性塑料中較小的分子量以及較寬泛的分子量分布促成方向性減少同時(shí)降低注塑件中的內(nèi)應(yīng)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外殼厚度比受加工變量影響的方式與方向性預(yù)測(cè)一樣；也就是它能隨融化或成型溫度及模腔壓力的增加而減少。拉伸強(qiáng)度和硬度隨外殼厚度比增加而增加。因而顯微鏡檢查提供了有效研究該工藝的另一方法。Advantages 優(yōu)點(diǎn)1. High production rates. For example, a CD disk can be produced with a 1012s cycle in high melt flow index PC.1. 高生產(chǎn)率：例如，一張CD盤在高融體流動(dòng)指數(shù)生產(chǎn)控制中只需1012s一個(gè)循環(huán)就

47、能生產(chǎn)出來。 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. 相對(duì)較少的工作內(nèi)容：一個(gè)操作者經(jīng)?？梢哉湛磧膳_(tái)以上機(jī)械，尤其是當(dāng)成品能自動(dòng)卸到輸送機(jī)上時(shí)。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. 零件幾乎不需要修整：例如，飛邊可以最小化并且模具能被設(shè)計(jì)成自動(dòng)將澆道和閘道從零件本身分離。4. Very complex shapes can be formed. Advances in mold tooling are largely responsible.4. 非常復(fù)雜的形狀也能成型：模具的進(jìn)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. 設(shè)計(jì)的靈活性(光潔度、顏色、插入物、材料)：通過復(fù)合注塑可以成型多于一種材料。可以高效地生產(chǎn)帶有固體外殼的泡沫型芯材料。熱硬化性塑料和纖維加強(qiáng)形狀都可以注塑成型。 6. Minimum scrap loss. Runner