外文翻譯---共射注塑成型技術(shù)

1、.附錄1 中文譯文共射注塑成型技術(shù)簡介和背景注塑擠壓成型法是大規(guī)模生產(chǎn)塑料制品最卓越的生產(chǎn)工藝。它是一種非常通用的生產(chǎn)方法。注塑成型允許生產(chǎn)幾何形狀非常復(fù)雜和幾何尺寸非常小的塑料制品。例如，一次性照相機的外殼就是通過注塑成型的方法生產(chǎn)出來的。像這一類塑料制品的幾何性狀經(jīng)常包括著幾條復(fù)雜的曲線、筋板、孔洞、圓柱型的凸臺和其他一些復(fù)雜結(jié)構(gòu)。到目前為止，為了進一步增強注塑成型法的有效性，擴大其適用范圍和增加收益率，注塑成型法的新的應(yīng)用和改良被不斷發(fā)展。共射注塑成型技術(shù)（Co-injection Molding）于是開始出現(xiàn)?，F(xiàn)在主要有兩種類型的聯(lián)合注塑成型技術(shù)。第一種被成為雙色成型法。雙色成型法的工

2、藝過程是先向模具中注射進一種樹脂材料，然后抽回模具的一部分零件（增加型腔空間）或?qū)⒁殉尚偷闹破忿D(zhuǎn)入到一個更大的型腔，并使其充分冷卻后，注射進第二種樹脂材料。這種技術(shù)被用來生產(chǎn)像計算機的按鍵和汽車的雙色尾燈之類的制品。第二種技術(shù)則更為普通，用第二種技術(shù)生產(chǎn)出來的制品通常包含不同的膚層材料和芯層材料。就像我們所熟知的“夾心三明治”一樣，因為芯層材料被包圍在膚層材料之間。夾芯成型技術(shù)是將兩種不同的塑料原料同時或者快速依次通過同一個澆口的有效注塑成型方法。一種塑料原料用來形成制品的內(nèi)部結(jié)構(gòu)，另外一種塑料原料組成制品的表面。通過組合兩種不同的塑料原料可以獲取原本傳統(tǒng)注塑成型方法所無法提供的好處。圖1一個

3、共射注塑機的結(jié)構(gòu)夾芯注塑成型技術(shù)在1969年被申請成為專利。它的最初發(fā)明目的是用來代替結(jié)構(gòu)泡沫塑料的生產(chǎn)工藝。傳統(tǒng)的結(jié)構(gòu)泡沫塑料的生產(chǎn)需要拋光和上色這樣的后續(xù)處理工藝。夾芯注塑成型技術(shù)可以一個由實體表面包圍的單元核來獲的很好的表面光滑度。這項生產(chǎn)工藝在1975年進入商業(yè)應(yīng)用。夾芯注塑成型生產(chǎn)過程由一臺擁有兩套彼此獨立的注塑控制單元的注塑機來完成。為了使兩種不同的塑料原料在注塑成型過程中通過同一個澆口，必須使用同一個噴嘴和一個轉(zhuǎn)換裝置。圖1說明了一個共射注塑成型注塑機的結(jié)構(gòu)。因為夾芯注塑成型技術(shù)與雙色注塑成型技術(shù)相比更為普通和具有代表性，接下來將重點討論夾芯注塑成型技術(shù)。共射注塑成型技術(shù)（Co-

4、injection Molding）的生產(chǎn)過程第一種使兩種不同的塑料注射進同一塑料制品成為可能的方法是按照以下的順序來完成的。這是使用同一個澆流道來完成的。圖2說明了了共射注塑成型生產(chǎn)過程中的生產(chǎn)步驟。圖2共射注塑成型的生產(chǎn)步驟。起初，向模具型腔內(nèi)注射進膚層材料，但并不是完全填充滿整個型腔。這就是我們所知道的“短射”。接下來的第二步向模具型腔注入芯層材料。同時一個冷凝層（膚層）開始在模具的型腔壁上形成。在接下來的一個階段內(nèi)，被注射進型腔內(nèi)的芯層材料幾乎完全充滿制品。產(chǎn)生此種現(xiàn)象的原因是：在注塑過程中形成的噴射流將影響已經(jīng)存在著的、且處于熔融狀態(tài)的膚層材料，將處在模具型腔中間的膚層材料推向模具型

5、腔表面，從而受冷產(chǎn)生制品的膚層。一旦模具被完全填充之后,少量的膚層材料被注射進澆道去清除掉澆道中的芯層材料，以防止在下一注射周期開始時澆道中的芯層材料被注射進制品的表面。單一澆道注塑成型法產(chǎn)生的問題是：在噴嘴轉(zhuǎn)換時將發(fā)生注射停滯，從而在制品表面上留下熔接線。另外這種注塑方法很難使芯層材料在制品中均勻分布。由于這些原因，單一澆道注塑成型法通常被用來生產(chǎn)芯層為泡沫塑料的厚壁制品。圖3 利用兩個同心注射通道進行的共射注塑成型另外一種有效的共射注塑成型方法是同時向模具型腔注射進兩種原料。入圖3所示。這種方法使用具有兩個同心流道的噴嘴。同時注射在保持溶流前鋒穩(wěn)定的流動速率方面具有明顯的優(yōu)勢，可以幫助避免

6、在制品的表面產(chǎn)生沖模流動痕跡，破壞制品的光滑表面。膚層材料和芯層材料在制品中所占的比例和分布情況基于這兩種原料的使用情況。主要因素包括兩種材料的黏度比值和體積比值。但是模具的幾何形狀和注塑生產(chǎn)過程的工藝情況（比如，注射速度）同樣也會對膚層/芯層材料的所占比例和分布產(chǎn)生影響。圖4說明了兩種不同材料的黏度比值對膚/芯層的分布影響。圖4 兩種不同材料的黏度比值對膚/芯層的分布影響?zhàn)ざ缺戎祵π緦釉谀w層中滲透長度和厚度的一致性起到了十分重要的作用。為了制品內(nèi)部獲得厚度較厚且均勻的芯層，可以通過模具中注了比膚層材料黏度稍厚的芯層材料來實現(xiàn)。膚層/芯層材料的黏度比值在決定最終產(chǎn)品的機械特性方面同樣具有十分重

7、要的意義。如果注塑過程中膚/芯層材料體積設(shè)置了一個不恰當(dāng)?shù)谋壤扔昧勘壤牟磺‘?dāng)），將造成芯層的材料打破膚層而流向制品的表面。這種芯層材料打破膚層而流向制品表面的現(xiàn)象是共射注塑成型中的常見缺陷。除了體積比例因素外，同時也基于注塑過程中的參數(shù)設(shè)置，比如注塑速度、芯層和膚層的注塑時間、熔體溫度和模具溫度。圖5說明了在一個連續(xù)共射注塑成型的案例中芯層和膚層材料的熔體長度與芯層材料打破膚層現(xiàn)象發(fā)生地點之間的關(guān)系。圖形被分為四個部分：1）膚層材料被注射進型腔。2）膚層材料停止注射，芯層材料被注射進型腔。3）芯層熔流前鋒膚層熔流前峰，但芯層熔流沒有打破膚層熔流（兩種材料開始混合）。4）芯層熔流前鋒打破膚

8、層熔流前峰（芯層材料將在制品表面出現(xiàn)）。圖5芯層和膚層材料的熔體長度與芯層材料打破膚層現(xiàn)象發(fā)生地點之間的關(guān)系5）圖6說明了模具設(shè)計對于芯層材料的分布影響。當(dāng)芯層材料被注射進型腔時，如果型腔的任何部分已經(jīng)被膚層材料完全填充，那么芯層材料是不可能被注射進模具型腔的。芯層材料無法穿透膚層到達其內(nèi)部因為已經(jīng)沒有空間來放置芯層材料?；谶@個原因，平衡流動在共射注塑成型中是十分重要的。圖6 模具設(shè)計對于芯層材料的分布影響共射注塑成型技術(shù)的優(yōu)點和缺點使用共射注塑成型法進行生產(chǎn)具有許多的優(yōu)點。使用共射注塑成型技術(shù)的主要原因之一是工業(yè)界對于日益增長的回收塑料的再利用?；厥绽脧U塑料是一項非常困難和昂貴的工作。許

9、多公司開始試圖使用共射注塑成型技術(shù)來解決這個難題。他們將回收的廢塑料作為芯層原料，而使用新塑料作為膚層原料。這項技術(shù)可以有效減少對資源的使用、減少回收利用的費用，從而減少廢棄塑料對環(huán)境做出貢獻。另為，使用共射注塑成型技術(shù)可以同時獲得幾種材料特性。最為普通的材料結(jié)合有實心的芯層和實心的膚層，或者實心的膚層和發(fā)泡的芯層。實心的芯層和實心的膚層的結(jié)合產(chǎn)生一系列的增強特性：減少了材料使用但增強了硬度，獲得了良好的表面光潔度并了剛度，表面是柔軟的但內(nèi)部確實硬的。實心的膚層和發(fā)泡的芯層同樣十分普遍。其主要思想是獲得空心泡沫結(jié)構(gòu)的好處并避免其缺點。一個空心泡沫結(jié)構(gòu)的芯層減少了材料的使用，降低了制品的重量和擁

10、有高強度。空心泡沫結(jié)構(gòu)的通常缺點是表面的光潔度，傳統(tǒng)的做法是對它們進行拋光和油漆。用共射注塑成型技術(shù)獲得的實心的膚層和發(fā)泡的芯層，原本額外的處理工序不再需要并且能夠提供很好表面光潔度。共射注塑成型技術(shù)的最大缺點是必須使用復(fù)雜的注塑成型機。而共射注塑成型注塑成型機與傳統(tǒng)的普通注塑成型機相比過于昂貴。事實上，共射注塑成型技術(shù)使用的一些特殊設(shè)備比傳統(tǒng)的注射成型設(shè)備貴出了50%-100%。由于出奇昂貴的價格，注射成型技術(shù)并沒有獲得很大范圍的接受。到1996年為止，也不到100臺注塑成型設(shè)備具有共射注塑成型能力。然而，隨著經(jīng)濟增長的需要和以環(huán)境保護角度出發(fā)的資源利用使使用共射注塑成型技術(shù)成為一種選擇。B

11、emis公司正在利用共射注塑成型技術(shù)生產(chǎn)座便器。許多自動車公司正在利用共射注塑成型技術(shù)解決汽車生產(chǎn)過程中造成的大量的廢棄塑料。;附錄2 英文原文Introduction and Background:Along with extrusion, injection molding is the most prominent process for mass-producing plastic products. It is a very versatile operation. Injection Molding allows for very complicated geometries an

12、d small dimensions. For example, the casing for disposable cameras is made via injection molding. The geometry for those pieces include several complicated curves, ribs, holes, protruding cylinders, and other elements. Even so, new applications and modifications of injection molding are being develo

13、ped to increase the usefulness, applicability, and profitability of injection molding. One such emerging technology is that of co-injection molding.There are two main types of co-injection molding. The first is referred to as two color molding. In two-color molding a part is molded using one resin,

14、and then a second resin is molded into the first once it is sufficiently cooled after some part of the mold retracts or the part rotates to a second larger cavity. This technology is used in products such as computer keys and multi-colored automotive taillights. The second, and more common, type of

15、co-injection molding involves the injection of a skin material and a core material. This is also known as “sandwich molding” because the core material is sandwiched in between the skin material. Sandwich molding is a variation of injection molding in which two different plastics are either simultane

16、ously or in rapid sequence injected through the same gate. One material makes up the core of the product and the other makes up the skin. Through the combination of two different materials several benefits can be extracted that traditional injection molding can not supply by itself. Figure 1: Sandwi

17、ch molding machine with a common nozzle and a switchieadThe sandwich injection molding process was patented in 1969. It was first invented to be an alternative to the structural foam process. Traditionally structural foam needed post-processing operations such as polishing and painting. The sandwich

18、 molding process could use a cellular core with a solid skin to obtain a good surface finish. The process has been commercially used since 1975. The sandwich molding process is achieved by a machine that has two separate and individually controlled injection units. Since the two materials are inject

19、ed through the same gate, they must have a common injection nozzle and a switching head. Figure 1 illustrates a sandwich molding machine. The sandwich molding process is more common than the two-color process, so the rest of this paper will focus on sandwich molding (referred to just as co-injection

20、 molding throughout the rest of the report).The Co-injection Molding Process:The first possibility for injecting the two materials is to do so sequentially. This is achieved using one channel. Figure 2 illustrates the steps in the sequential co-injection process. Initially, a shot of the skin materi

21、al is injected into the mold but does not completely fill it. This is known as a “short shot.” In the next step the core material is injected. A frozen layer begins to form at the cold mold walls. In the next stage, a shot of the core material is injected to almost completely fill the part. The phen

22、omena known as the fountain flow effect of polymer inside the mold will cause the skin material that is still in the melt phase near the center of the mold thickness to be pushed out against the mold walls creating the skin layer. Once the mold is almost filled, a small amount of skin material is in

23、jected to purge the core material from the spruce to eliminate any possibility for it to show up at the surface of the next shot. The problem with the one-channel method is that stagnation occurs at the switch-over which results in a “hesitation line” in the shape of a dull ring. Also, it is difficu

24、lt to achieve a uniform distribution of the core material. For this reason, the one-channel method is usually reserved for thick-walled parts with a foam core.Figure 1: Illustrations of the stages in sequential co-injection molding through a single nozzleThe other possible co-injection method is sim

25、ultaneous injection of the two materials. This method utilizes nozzles with concentric flow channels such as those shown in figure 3. Simultaneous injection has the advantage of maintaining a constant flow-front velocity which helps to avoid flow marks and differences in gloss.Figure 2: Concentric i

26、njection channels used for simultaneous co-injection moldingThe ratio and distribution of the skin and core material depends on the materials used. The primary factors are the viscosity ratio of the two materials and the volume ratio, but it is also affected by mold geometry and the processing condi

27、tions (i.e. injection speed). Figure 4 illustrates the effect that viscosity ratio can have on the skin/core distribution. It plays an important effect in determining the thickness uniformity and length of core penetration. The most uniform thickness distribution can be achieved by injecting a core

28、that has a slightly higher viscosity than the skin. The viscosity ratio also had a significant effect on the mechanical properties of the final product. Using an improper volume ratio can give rise to the core material breaking through the skin material to the surface of the product.Figure 4: Illust

29、rating the effects of the viscosity ratio on the thickness distribution of the core materialThe breakthrough phenomenon is a common defect in co-injection molding. Besides the volume ratio it is dependent on the processing conditions such as injection speed, injection time of the core and skin mater

30、ials, melt temperature and mold temperature. Figure 5 illustrates the relationship between flow length of both the skin and core materials for a sequential co-injection molding process for a case where the breakthrough phenomenon occurs. The graph is divided into four regions: 1) the skin material i

31、s injected, 2) the skin injection stops and the core material is injected, 3) the core flow front reaches the skin flow front but does not break through (the two material advance together), 4) the core flow front breaks through the skin flow front (the core material will appear at the surface of the

32、 product.Figure 5: Flow length relationship with injection time for core and skin when breakthrough occursFigure 6: Illustrating the effects of mold cavity geometry on the core material distributionThe affect of mold design on core distribution is illustrated by figure 6. The core will not penetrate

33、 any part of the mold that has already been completely filled by the skin material when the core is injected. It cannot penetrate the skin material because there is no room to displace it. For this reason, a balanced flow is very important in co-injection molding.Advantages and Disadvantages:There a

34、re many advantages to using the co-injection molding process. One of the main factors driving co-injection technology is the growing need for recycling in industry. Recycling wasted plastic is very difficult and costly to do. In order to solve this problem, many companies are attempting to use co-in

35、jection where recycled plastic is used as the core material and virgin material is used as the skin material. This technique can significantly reduce material and recycling costs along with the environmentally friendly reduction of waste. Also, some beneficial material properties can be achieved wit

36、h through the use of co-injection molding. The most common combinations of materials used are a solid skin and solid core, or a solid skin and a foam core. The solid skin and solid core combination can create a number of enhanced properties: high rigidity with reduced material costs, good surface finish with increased rigidity, and flexible surface with rigid core. The solid skin and foam core combination is also very common. The main idea is to provide the benefits of foam without the disadv