模具設計外文翻譯塑料成型過程

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1、外文翻譯原文 Plastics forming processes There is a wide range of processing methods that may be used for plastics. Nevertheless, they all involve three or four basic stages: softening, shaping, solidifying and cooling of the moulds (for thermoplastics only). C

2、ommon materials for moulding processes are thermoplastics and thermoset polymers. Principal methods of processing thermoplastics include extols ion, blow moulding, rotational moulding, thermoforming and injection moulding; but as for thermosets, compression, transfer and reaction injection moulding

3、are frequently used. 1 Extrusion Extrusion is one of the most important forming processes for the reason that pellets, which are used for many other moulding processes, are normally produced by this process. In fact, some moulding processes are post-extrusion operations, such as blow moulding a

4、nd thermoform moulding. Extnlsion is basically a process of continuously shaping a fluid polymer through the orifice of a die, and subsequently solidifying it into a product of a uniform cross-section. An extruding machine may have one or two screws, or no screw (screwless). Single-screw extruders,

5、as seen in Figure 1, are the most commonly used machines. Screwless (ram) extruders allow a precise control of the melt flow rate and are gaining popularity. They are particularly suited for high viscosity. In recent years, there has been a steady increase in the use of twin screw extruders. These m

6、achines permit a wider ranger of possibilities in terms of output rates, mixing efficiency and heat generation. They are, however, considerably more expensive.Common extrusion products include filaments of circular cross-section, profiles of irregular cross-section, axisymmetric tubes and pipes, and

7、 flat products such as films or sheets. Almost all types of intricate cross-sectional shapes with large lengths are made by extrusion moulding, which many other discrete forming processes, such as compression, transfer and injection moulding, are incapable of producing. FIGURE 1.Si

8、ngle-screw extruder. 2 Blow moulding This process begins with the preparation of a soft, extruded and preformed thermoplastic tube over a core pin.As the mould halves close, air pressure inflates the thinwalled preform and forces it outwards against the mould sides. Figure 2 shows the process

9、 at two stages. The preform can be made by either extras ion or injection. Blow moulds are subjected to moderate pressures and clamping forces, compared to injection moulds. Thus, they can be made of a light material such as aluminmm, which has advantages of light weight and high heat conductivity.

10、 Blown-ware containers are commonly used for packaging beverage and other fluid food, e.g. narrow neck plastic bottles for mineral water, milk, alcoholic beverage and carbonated beverages. Other non-food products packed in the blown-ware containers include cosmetics, pharmaceuticals, paint and powde

11、r products. Blow moulding is also used to produce some huge products in size, such as shipping drums and stationary storage tanks whose volumes may reach as high as 10 000 litres [5]. These tanks are used for underground fuel storage and septic tanks. Stage 1: Preform extrusion Stage 2: Bl

12、owing FIGURE 2.Extrusion blow moulding 3 Rotational moulding Like blow moulding, rotational moulding is also used to produce hollow plastic articles, though the principles in each method differ a lot. During the process, a carefully weighed charge of plastic powder is placed

13、in one half of a metal mould. The mould halves are then clamped together and heated on an oven. When heated, the mould rotates about two axes at right angles to each other. After a time the plastics will be sufficiently softened to form a homogeneous layer on the surface of the mould. The process is

14、 attractive for a number of reasons. Firstly, as it is a low-pressure process, the moulds are relatively simple and inexpensive. Secondly, the product is virtually strata-free. Thirdly, a uniform thickness can be easily achieved. Finally, it is possible to introduce reinforcement into the products,

15、and their surface can be textured as desired. However, the cycle times are longer compared to blow or injection moulding. The mould-handling device, capable of imparting double rotations, is the central element of rotational moulding equipment. There are two major types of equipment: shuttle cart sy

16、stem, as shown Figure 3, and swing/rotary arm system. Rotational moulding is good at producing very large, thick-walled articles which could not be produced economically by any other processes. The largest capacity of a rotational-moulding made tank is recorded at about 75 000 litres [4]. FIGURE

17、3.Shuttle cart rotational moulding. The Institution of Professional Engineers New Zealand 4 Compression moulding Compression moulding is often used to produce articles from thermoset materials, though it can also be used for thermoplastics. The moulding operation used for thermosets is

18、illustrated in Figure 4. A large number of compression moulded thermoset products can be found in electrical and electronic applications. Glass-fibre reinforcement can be easily added to meet the heat resistance requirement. However, the limitation with this process is that the product has to be sim

19、ple in shape and without thin walls or fragile inserts. Numerous rubber products are compression moulded. A useful feature of it is its ability to have metal inserts that form strong bonds with the product and are often used to attach the product to structures. Tyres are the most common products mad

20、e by compression moulding. FIGURE 4.Compression moulding. 5 Transfer moulding Transfer moulding is similar to compression moulding except that, instead of the moulding material being pressurised in the cavity, it is pressurised in a separate chamber and then forced through an opening and i

21、nto a closed mould cavity. The advantage of transfer moulding is that the preheating of the material injected through a narrow orifice improves the temperature distribution in the material and hence accelerates the cross-linking reaction in thermosets. As a result the cycle time is reduced and there

22、 is less distortion in the product. The improved flow of material also means that more intricate shapes can be produced. Parts with fragile inserts like electric appliance parts, electronic components and connectors that may enclose coils, integrated circuits, and plugs can also be easily made. 6

23、 Thermoforming Sheet thermoforming was developed in the 1950s. The limitations such as poor wall thickness distribution and large peripheral waste restricted its use to simple packaging applications. In recent years, however, there have been major advances in machine design and materials, which ha

24、ve resulted in a wide range of products being made by thermoforming. There are three types of thermoforming processes (Figure 5): vacuum moulding, air pressure moulding, and mechanical moulding. The moulds, which are not subjected to high pressure, are often made from cast or machined alumininm for

25、 small and medium sizes, and they do not require a good surface finish. The product surface quality is largely dependent upon that of the sheet material. Products made by thermoforming can be small as well as large. Smaller products are made in high output machines, using multi-cavity moulds. Such

26、products are often found in the food industry and medical applications, for example, jelly or cream containers, cups, robs and trays. These small items can have relatively complex shapes with reasonably even thickness. Large products are generally made from cut sheets at a lower though-put rate, and

27、 they are usually of simple shapes. Fisher & Paykel's vacuum form moulding machines produce the majority of pre-forms for refrigerators and freezers. Many other interior parts are also made by the same or similar processes. FIGURE 5.Three basic methods of thermoforming. 7 Inje

28、ction moulding Injection moulding has always been one of the most common processing methods for plastics. Nowadays countless parts in many electrical appliances, automobiles and office equipment are injection moulded. The most common injection moulding machinery is the reciprocating screw machine,

29、whose process can be divided into several stages as seen in Figure 6. At the plastication stage, the feed unit operates as an extntder, melting and homogenising the material in the screw/barrel system. The screw, however, is allowed to retract in order to make room for the molten material in a space

30、 at the cylinder head, called material reservoir, between the screw tip and a closed valve or an obstntction of solidified material from the previous shot. At the injection stage, the screw is used as a ram (piston) for rapid transfer of the molten material from the reservoir to the cavity between t

31、he two halves of the closed mould. Since the mould is kept at a temperature below the solidification temperature of the material, it is essential to inject the molten material rapidly enough to ensure complete filling of the cavity. A high holding or packing pressure is normally exerted, to partiall

32、y compensate for the thermal contraction of the material upon cooling. The cooling of the material in the mould often limits the production time because of the low thermal conductivity of polymers. The mould, after being cooled, can be opened and the solid product ejected. Although the screw machin

33、e is by far the most popular, plunger injection machines are also used to give products some unique features. There is no shearing or mixing action, as a plunger does not rotate. The resulting moulded part can take on a marbled appearance with swirls of two or more colours. This may be the desired f

34、inish for certain products. Regardless of different machines, injection moulding yields a high productivity and allows the products to have many fine details such as bosses, location pins, mounting holes, bushings, ribs, flanges, etc. All these features can eliminate many subs equent assembly and fi

35、nishing operations. A large variety of products can be injection moulded. These include (a) micro-products, moulded in multiple cavity moulds on small precision machines, such as components for watches and microelectronics; (b) medium size products, moulded continuously in very large numbers in ded

36、icated machines or in relatively small runs; and (c) large products, moulded by large machines, such as car dashboard frames, TV cabinets, garden furniture, and small boat hulls. Many of these large plastic parts have a solid skin and a cellular inner structure, hence the process is also known as st

37、ructural foam moulding. FIGURE 6. Sequence of operations in injection moulding. 8 Reaction injection moulding Reaction injection moulding is a relatively new process, which involves the rapid mixing, in precise proportions, of two or more highly reactive liquid components and the i

38、mmediate injection of the mixture in a closed mould Polymerisation takes place in the mould in a very short period of time, yielding a solid product. The process is particularly suited to the production of large and relatively thin parts, with less capital investment and operating costs than in ther

39、moplastic injection moulding. The process is also energy efficient, but requires good control of complex reactions. 9 Conclusions By and large, each moulding process mentioned above has its pros and cons in terms of the materials, products and cost. The plastics industry plays an important role i

40、n today's manufacturing industry. Plastics moulding is the most popular process. Whereas injection moulding continues to dominate the sector, other moulding processes make some important contributions toward manufacture of many specific products. Faced by numerous challenges, new processes are makin

41、g their way into the market. Conscious of energy consumption, moulding machine manufacturers are contemplating innovative designs to economise on the process. There is also a demand for these manufacturers to develop either smaller or larger moulding machines to meet customer demands. The fact that

42、more and more newly developed materials use moulding processes for a manufacturing method provides an extra dimension for the development of the moulding industry. 外文翻譯譯文 塑料成型過程 有很多關于塑料成型的方法。盡管如此，它們都包跨三個或者四個基本環(huán)節(jié)：軟化、修整、凝固、模具冷卻（僅適用于熱塑性模具）

43、。一般的對于模具成型過程的材料是熱塑性和熱固性的聚合體。主要的處理熱塑性塑料的方法包括等離子法、吹鑄法、旋轉鑄法、加熱成形法、注塑模法，但是關于熱固性塑料，壓縮法、轉移法和反推注塑法常常被使用。 1 擠壓法 擠壓法是最重要的成形方法之一因為用作許多其它的模制過程的小球很普遍地在這個過程中被引長。事實上，一些模制方法是一些加速擠壓的操作，如吹模法和加熱成形模制法。擠壓法是一個通過模具孔和后來把它固化為的一個統(tǒng)一的橫截面的不斷修正流動聚合體的基本過程。一個擠壓機擁有一個或者兩個螺桿，或者沒有螺桿（無螺桿型）。單一螺桿擠壓機，正如圖形1所示，是最通常使用的機器。無螺桿型（撞錘型）擠壓機通常

44、流行為開槽型并且允許對熔體流動率的精確控制。他們特別適合高粘度的場合。近些年，對雙螺桿擠壓機的應用已經有了穩(wěn)定的增長。這些機器根據(jù)產出率、混合效率、生熱性允許一個寬的可能性范圍。盡管如此他們相比較而言更加的貴。普通的擠壓產品包括圓形橫截面的細絲、不規(guī)則橫截面的側面、軸對稱的管子、和諸如薄片或者薄膜之類的扁平軋材。幾乎所有有很大尺寸的復雜的代表性形狀都是用擠壓模制做成的，許多是其它單獨的成型過程，諸如壓制、移動和注塑成形難以生產的。 圖片1.單絲杠擠壓機 2 吹鑄成型 這個過

45、程從準備一個軟的被擠壓了并且預成型的壓在中心梢上的熱塑料性軟管開始。當模具關攏時，空氣壓力會使得薄壁的成型腔膨脹并使它向外地擴張模具面。圖片2展現(xiàn)了這兩個時期的過程。這個預先變形可以由增加元素和注塑形成。相比較注塑模而言，吹塑模需要適中的壓力和夾緊力。所以，他們可以由一種比較輕的材料組成，比如鋁，它有重量輕和高熱傳導性等優(yōu)點。 吹塑容器一般被用來包裝飲料和其它液體食物。窄瓶頸塑料瓶子則被用來裝礦物質水、牛奶、酒精飲料、碳酸飲料。其它的非食用產品被包裝在吹鑄容器中包括化妝品、醫(yī)藥品、油漆和粉末產品。吹鑄品也被用在生產一些大型的產品上，如船倉和固定的儲油罐，它們的容積也許會達到10000毫升之高

46、。這些容器被用來作為地下燃料儲藏庫和化糞池。 時期一 預先成型擠壓 時期二 吹鑄 圖片2.擠壓吹鑄模具 3 旋轉鑄模 如吹鑄模具，旋轉鑄模也被用來生產空洞的塑料商品，盡管每種方法的原理有很大的不同。在這個過程中，一個經過仔細稱重得到的塑料粉末置于一半的金屬模中。然后這一半模具被夾在一起并在一個爐里面進行加熱。當加熱好以后，模具關于兩個軸進行每次90°的旋轉。在一段時期之后，塑料將均勻地軟化在模具表面上形成一個相似層。這個過程是很有魅力的，這里有很多原因存在。首先

47、，它是一個低壓力過程，模具相應就比較簡單和便宜。第二，產品事實上是免費的。第三，均勻厚度可以很簡單地被實現(xiàn)。最后，就可以進行產品加固，他們的表面可以按照要求達到。盡管如此，周期相比于吹鑄或者注塑要長。模具操作裝置，可以安裝雙旋轉，是旋轉模具設備的中心元件。有兩個主要的設備類型：穿梭車系統(tǒng)，如圖像3所示，和搖擺臂系統(tǒng)。旋轉模具非常適于生產那些非常大的有厚墻的用其它過程難于很經濟地生產的產品。最大的旋轉模容積被記載大約有75000升左右。 圖片3.穿梭車轉動模

48、 新西蘭職業(yè)工程師協(xié)會 4 壓縮模制 壓縮模型通常被用來生產熱固性材料商品，盡管它也可以被用于生產熱塑性塑料。用作熱固塑料的鑄模操作插圖于圖4。一個很大的數(shù)目的模制熱固塑料產品能夠在電力和電子應用中得到發(fā)現(xiàn)。玻璃纖維增加層能夠輕松地增加材料的熱抵抗要求。盡管如此，這個過程的局限性是產品必須形狀簡單而且沒有薄壁或者易碎內嵌物。很多的橡膠產品都是壓縮模制的。它的有用的外表是它有可以形成強大的產品鐐銬的金屬內嵌物經常被用來聯(lián)系產品與框架。輪胎是壓力鑄模的最普通的產品。 圖片4. 壓縮模

49、制 5 移動模制 移動模制與壓縮模制很像，除了那個，取代將材料壓縮在容器里，它被壓縮在一個分模鏜里然后壓縮在一個開闊空間中然后被壓縮在一個封閉的模具容器中。移動模具的好處是材料的預熱通過一個窄的空洞注入增加了溫度在材料中的分配所以促進了熱固塑料的橫向連接反作用力。結果是周期減少了并且產品的扭曲也減少了。物資流程的改進也意味著更多的復雜情況能夠被生產。有易碎內嵌的零件如電力內嵌零件、電子元件和放入封套的連接器、集成電路和插栓也能夠輕松地被生產出來。 6 熱力塑形 薄片熱力塑形是在1950年被發(fā)展起來的。限制諸如弱薄墻分部和大的外圍浪費把它的用途限制在簡單的包裝應用上面了。盡管

50、如此，在近年來，在機器設計和材料方面已經有了很大的進步，已經有了一個很廣的熱力塑形的產品系列。有三種熱力塑形過程的形式(圖5)：真空成型、空氣壓力成型、和機械成型。 這些不受高壓的模具，通常來自鑄造的或者車出來的小型或者中型的鋁材，它們不需要一個好的表面成型。零件表面質量很大程度上取決于薄材。 熱力塑形產品可小可大。小的產品在高輸出機械里運用多槽模具制造。這些產品通常能在食品和醫(yī)藥行業(yè)中看到，舉個例子，剩果子凍或者奶油的容器、杯子、彎管和碟子。這些小的項目能夠相應地有一些帶有適度厚度的復雜的形狀。大型的產品通常由切片在很低的輸入速率下制成，而且它們通常都是簡單的形狀。費舍爾和佩凱爾的真空鑄

51、模機器聲場著最大的預成型用作冷藏庫和冷凍之用。許多其它的內部零件也是由相同或相似的過程制成的。 圖片5. 三種基本的熱力塑形方法 7 注塑模具 注塑模具一直是一種最普通的塑形成型方法?，F(xiàn)今數(shù)不清的電力應用、手機和辦公儀器里的零件都是注塑模制的。最普遍的注塑模具機器是過程如圖片6所示可以被分為幾個時期的往復擺螺桿機器。在增塑階段，伺服單元操作如一個電爐，融化在絲桿和桶內的材料。絲桿，盡管如此，是允許回縮在圓柱頭空間上來為融化材料提供空間，被稱為蓄水池通常在絲桿梢和封閉閥之間或者來自先前槽的固化材料

52、。在注塑階段，絲桿是用作一個活塞來提供融化材料在兩個封閉模閥之間從蓄水池到容器的快速移動的。因為模具的溫度控制在固化溫度以下，足夠快地注射模具來確保容器的完全充滿是很重要的。一個高的支持或者包裝壓力通常是很有用的，能夠部分地補償材料在冷卻下的熱形式收縮。模具中材料的冷卻通常限制了生產時間因為聚合體的低熱傳導性。模具，在被冷卻之后，便可以開模并且固體的產品被噴出。 盡管絲桿機器到目前為止是最流行的，活塞注塑機器也被用來給予產品一些獨特的外觀特征。沒有剪切或者混合的動作，因為活塞不轉動。最后的模制零件可以運用兩種或多種旋轉顏色來作一種大理石的修飾。這也許是一定產品渴求的完成品。無論機器怎么的不同

53、，注塑模具生產一種高生產率產品并確保產品有許多很號的細節(jié)如滾花、定位栓、固定孔、軸襯、肋骨、凸緣等等。所有的這些特征都能夠消除許多低平衡裝配和最后工序。 很大一部分產品都能注塑模制的。其中包括 (a) 微小產品、在小精密度上的，多腔模具，如表元件和微電子元件；(b) 中等尺寸產品，在精確機器或者相對旋轉以非常大的數(shù)目連續(xù)安裝，和 (c) 大型產品，由大型機器模制，如汽車的儀表板結構、電視機箱、花園家具、和小型船體。許多大型的塑料零件都有穩(wěn)固的表面和蜂窩狀的內部結構，所以這個過程也是一個結構的泡沫模制。 8 反作用注塑模 反作用注塑模具是一個相應地新的過程，包括快速混合、精確比例、兩

54、個或更高反應液體部分和快速注塑混合物到一個封閉模腔在模具中用很短的時間發(fā)生反應產生固體產品。這個過程特別適于生產相比于熱塑性注塑模的大型和相應基金總額少花費少的薄壁零件。這個過程也是能耗的，但是需要對復雜反應的良好控制。 9 總結 大體上，每個模制過程要考慮的主要是材料、產品、花費中的正反兩方面。塑料工業(yè)在當今的制造工業(yè)中起著重要的作用。塑料模制是最流行的過程。與此相反注塑模具繼續(xù)統(tǒng)治 圖片6. 注塑模操作順序 著這個部門，其它的模制過程對生產特殊產品起著作用。面對著種種挑戰(zhàn)，新的工序使得他們走向市場。意識到能量的消耗，模制機器生產商們開始注重革新性設計來節(jié)約這個過程中的能量損耗。對這些生產商們也有一個需求就是發(fā)展更小或者更大的模制機器來滿足消費者的需求。事實上是越來越多新發(fā)展的材料用模制過程來為模具工業(yè)的發(fā)展提供一個新增的維度。