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2024-11-13 21:12本頁(yè)面
【正文】 to be molded and the provisions necessary for product ejection. Injectionmolded products can be classified as: ○ 1 Products without undercuts(., plaques, strips, halfshells, cups). ○ 2 Products with external undercuts or lateral openings(., spools and bobbins, beverage crates, threaded bolts). ○ 3 Products with internal undercuts (., threaded closures, housings). ○ 4 Products with external and internal undercuts(., 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 mon 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 use
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