【正文】 Many molds, particularly molds for larger products, are built for only cavity space, 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 4cavity mold requires only onefourth of the machine time of a singlecavity mold. Conversely, the production 桂林電子科技大學畢業(yè)設計（論文）報告用紙 7 increases in proportion to the number of cavities. A mold with more cavities is more expensive to build than a singlecavity mold, but not necessarily 4 times as much as a singlecavity mold. But it may also require a larger machine with larger platen area and more clamping capacity, and because it will use 4 times the amount of plastic, it may need a large injection unit, so the machine hour cost will be higher than for a machine large enough for the smaller mold. . Cavity shape and shrinkage The shape of the cavity is essentially the ―negative‖ of the shape of the desired product, with dimensional allowance added to allow for shrinking of the plastic. The shape of the cavity is usually created with chipremoving machine tools, or with electric discharge machining, 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 certain metals in plaster molds created from models of the product to be made, or by casting some suitable hard plastics. The cavity shape can be either cut directly into the mold plates or formed by putting inserts into the plates. . Cavity and core By convention, the hollow portion of the cavity space is called the cavity. The matching, often raised portion of the cavity space is called the core. Most plastic products are cupshaped. 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. 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 side. . Polymer Processing Polymer processing, in its most general context, involves the transformation of a solid (sometimes liquid) polymeric resin, which is in a random form (., powder, pellets, beads), to a solid plastics product of specified shape, dimensions, and properties. This is achieved by means of a transformation process: extrusion, molding, 桂林電子科技大學畢業(yè)設計（論文）報告用紙 8 calendaring, coating, thermoforming, etc. The process, in order to achieve the above objective, usually involves the following operations: solid transport, pression, heating, melting, mixing, shaping, cooling, solidification, and finishing. Obviously, these operations do not necessarily occur in sequence, and many of them take place simultaneously. Shaping is required in order to impart to the material the desired geometry and dimensions. It involves binations of viscoelastic deformations and heat transfer, which are generally associated with solidification of the product from the melt. Shaping includes: twodimensional operations, . die forming, calendaring and coating。 The home appliance mould annual growth rate will exceed 10 %。編號： 畢業(yè)設計 (論文 )外文翻譯 （原文） 院 （系）： 機電工程學院 專 業(yè)： 機械設計制造及其自動化 學生姓名： 莫 飛 學 號： 0801120436 姓 名： 呂汝金 職 稱： 講 師 2020 年 5 月 15 日 桂林電子科技大學畢業(yè)設計（論文）報告用紙 1 The Injection Molding The present situation that the mould makes at present and trend The mold is at the core of a plastic manufacturing process because its cavity gives a part its shape. This makes the mold at least as criticaland many cases more sofor the quality of the end product as, for example, the plasticiting unit or other ponents of the processing equipment. The mould is important handicraft equipment， occupies decisive position in industrid departments such as consumer goods， electrical equipment electron，automobile , aircraft fabrication. The mould is important handicraft equipment , occupies decisive position in industrid departments such as consumer goods，electrical equipment electron， automobile , aircraft fabrication. Industrial product part rough process 75%, the finish machining 50% and plastic part 90% will be pleted from the mould. The Chinese mould market demand already reaches scale of 500 hundred million yuan at present. The automobile mould , the annual growth rate covering piece of mould especially will exceed 20 %。 Also prompt building material mould development， various heterotype material the mould， wall surface and floor mould bee new mould growth point, plastic doors and windows and plastic drainpipe increase to exceeding 30 by in the uping several years %。 The IT industry year increases % speed equally exceeding 20， the need to the mould accounts for 20 of mould marketplace %.2020 annual Chinese machine tools implements industry output value. Will continue to increase. Our country mould fabrication market potential is enormous. The basis data counts， in recent years， our country mould year gross output value reaches 3