外文翻译--注塑模具

外文翻译--注塑模具内容摘要：

mold, but (as in our example)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 (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, 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 , 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 chipremoving 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 (., epoxy resins).The cavity shape can be either cut directly into the mold pla。