外文翻译-- 注塑模具.doc

Injection MoldsA. Basic mold designAn injection mold consists of at least two halves that are fastened to the two platens of the injection molding machine so that they can be opened and closed. In the closed position, the product-forming surfaces of the two mold halves define the mold cavity into which the plastic melt is injected via the runner system and the gate. Cooling provisions in the mold provide for cooling and solidification of the molded product so that it can be subsequently ejected.B. Types of Ejection For product ejection to occur ,the mold must open. The shapes of the molded product determines whether it can be ejected simply by opening the two mold halves or whether undercuts must be present. The design of a mold is dictated primarily by the shape of the product to be molded and the provisions necessary for product ejection. Injection-molded products can be classified as:Products without undercuts(e.g., plaques, strips, half-shells, cups).Products with external undercuts or lateral openings(e.g., spools and bobbins, beverage crates, threaded bolts).Products with internal undercuts (e.g., threaded closures, housings).Products with external and internal undercuts(e.g., bumper fascias, electrical and automotive instrument housings, cameras, etc.).C. Design Rules There are many rules for designing molds. These rules and standard practices are based on logic, past experience, convenience, and economy. For designing, mold making, and molding, it is usually of advantage to follow the rules. But occasionally, it may work out better if a rule is ignored and an alternative way is selected. In this text, the most common rules are noted, but the designer will learn only from experience which way to go. The designer must ever be open to mew ideas and methods, to new molding and mold materials that may affect these rules.D. The Basic Mold 1. Mold Cavity Space The mold cavity space is a shape inside the mold, ”excavated”(by machining the mold material) in such a manner that when the molding material(in our case, the plastic)is forced into this space it will take on the shape of the cavity space and, therefore, the desired product The principle of a mold is almost as old as human civilization. Molds have been used to make tools, weapons, bells, statues, and household articles, by pouring liquid metals (iron, bronze) into sand forms. such molds, which are still used today in foundries ,can be used only once because the mold is destroyed to release the product after it has solidified. Today, we are looking for permanent molds that can be used over and over .Now molds are made from strong, durable materials, such as steel, or from softer aluminum or metal alloys and even from certain plastics where a long mold life is not required because the planned production is small. In injection molding the (hot) plastic is injected into the cavity space with high pressure, so the mold must be strong enough to resist the injection pressure without deforming. 2 . Number of Cavities Many molds, particularly molds for larger products, are built for only 1 cavity space(a single-cavity mold),but many molds, especially large production molds, are built with 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 4-cavity mold requires only (approximately) one-fourth of the machine time of a single-cavity mold. Conversely, the production increases in proportion to the number of cavities. A mold with more cavities is more expensive to build than a single-cavity mold, but (as in our example)not necessarily 4 times as much as a single-cavity mold .But it may also require a larger machine with larger platen area and more clamping capacity, and because it will use (in this example) 4 times the amount of plastic, it may need a larger injection unit, so the machine hour cost will be higher than for a machine larger enough for the smaller mold. Today, most multicavity molds are built with a preferred number of cavities:2,4,6,8,12,16,24,32,48,64,96,128.These numbers are selected because the cavities can be easily arranged in a rectangular pattern, which is easier for designing and dimensioning, or manufacturing, and for symmetry around the center of the machine, which is highly desirable to ensure equal clamping force for each cavity. A smaller number of cavities can also be laid out in a circular pattern, even with odd numbers of cavities, such as 3, 5, 7 , 9.It is also possible to make cavity layouts for any number of cavities, provided such rules as symmetry of the projected areas around the machine centerline are observed. 3. Cavity Shape and Shrinkage The shape of the cavity is essentially the ”negative” of the shape of the desired product, with dimensional allowances added to allow for shrinking of the plastic. The shape of the cavity is usually created with chip-removing machine tolls, or with electric discharge machining (EDM), 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 (and then machining) certain metals (usually copper or zinc alloys) in plaster molds created from models of the product to be made, or by casting (and then machining) some suitable hard plastics (e.g., epoxy resins).The cavity shape can be either cut directly into the mold plates or formed by putting inserts into the plates.E. Cavity and Core By convention, the hollow (concave) portion of the cavity space is called the cavity. The matching, often raised (or convex) portion of the cavity space is called the core. Most plastic products are cup-shaped. 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. Usually, the cavities are placed in the mold half that is mounted on the injection side, while the cores are placed in the moving half of the mold. 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 (“hot”) side.注：该文选自 张晓黎 李海梅主编。 塑料加工和模具专业英语化学工业出版社，2004 注塑模具A基本模具设计一个注塑模具至少包括两半，这些固定在两个盘的注塑机，以便他们能够开启和关闭。在关闭位置，产品形成表面两个半确定模具型腔将其注入塑料熔体通过热流道系统和门。冷却规定提供模具冷却和凝固的成型产品，以便能够随后顺利流出.B 注塑的类型产品注射发生时，模具必须打开。制品的形状决定了它是能够被直接开模取出还是必须考虑凹孔的影响。模具的设计是决定模具的形状主要是由该产品将成型的规定和必要的产品注射。注塑产品可分为： 1Products不削弱（如斑块，带，半弹，杯） 。 2Products与外部削弱或侧开口的（例如，线轴和筒子，饮料箱，螺纹螺栓） 。 3Products内部破坏（例如，线程关闭，外壳） 。 4Products与外部和内部破坏（例如，保险杠fascias ，电器和汽车仪表外壳，照相机等） 。C.设计规则设计模具有许多规则。这些规则和标准的做法是根据逻辑，过去的经验，方便， 经济的角度考虑的.对于设计，模具制造，成型，按照这些规则通常是有优势的.但是有些时候，它可能更好的工作如果忽视了这种方法而选择可另一种设计原则.在这段文章中，最常见的规则被选择，但设计者将会根据经验去确定应该选择的规则，同时设计者必须想出新的方法和建议去设计新的模具和模具材料，这些可能会影响到这些规则。D.基本模具1.模具型腔空间在模具型腔形状空间内的模具， “挖掘” （由机械加工的模具材料）以这种方式，当成型材料（在目前情况下，塑料）是被迫进入这一领域将采取的形状腔的空间，因此，得到理想的产品.模具的这一原理几乎和人类文明有一样漫长的历史.模具已被用来制造工具，武器，钟声，雕像，和家居用品，通过浇注液态金属（铁，铜）到沙形式。这种模具，这是沿用至今的铸造厂，但是只能使用一次，因为为了在产品固化后将其取出而不得不将其毁坏.今天，我们正在寻找永久铸模，可重复使用。现在的模具都是用坚固的，可回收利用的材料做成的，比如钢铁，软铝或金属合金。某些塑料模具在长期的生活并不需要，因为计划生产量本来就少。在注塑成型的（热）塑料注入腔空间用高压，因此，模具必须强大到足以抵制注射压力不变形。2.型腔的数目许多模具，特别是较大的模具产品，是专为只有1腔空间（单腔模具） ，但许多铸模，尤其是大型的生产模具，建有或更多的型腔，这个原因完全是从经济的角度考虑的。It这样就只需要投入稍微多一点的时间去注入几个型腔而不是仅仅的一个 。例如，一个4腔模具只需要（约）的四分之一的时间注入一个单腔模具。总之，产量的增加完全可以根据型腔数目的增加而增加。当然也个拥有多个型腔的模具要远比只有一个型腔的模具昂贵的多，但（因为在我们的例子）不一定就比单腔模具