模具毕业设计外文翻译--表面处理如何延长模具运行周期-模具设计(编辑修改稿)

模具毕业设计外文翻译--表面处理如何延长模具运行周期-模具设计(编辑修改稿)内容摘要：

coatings. Because applying nickelboron nitride is an autocatalytic process, it requires no anode, therefore saving time and money. In addition, it will not promise thermal conductivity of the mold. Applications include unscrewing cores for closures, where reduced cycle times are essential. Where lubricity is needed for better release from deep ribs, zerodraft cores, textured surfaces and “sticky” polymers, a nickelPTFE posite will greatly improve part release and enhance resin flow by as much as 4 to 8 percent for shorter cycle times. COF is against steel. It should be noted that applying pure PTFE to the mold adds high lubricity, but only a very shortterm benefit. PTFE by itself has no hardness, so it won’t last. But a dispersion of 25 percent PTFE by volume in a codeposit with nickel results in 45 RC hardness for added wear and corrosion protection. Tried and True Despite the new coating science, we cannot throw out the old, reliable coatings such as like hard chrome or electroless nickel just yet. There’s no question that they still have their uses. Hard Chrome For example, hard chrome’s top advantage is that it has a hardness of 72 Rockwell C (RC) and is applied at the low temperature of 130oF. When applied in its purest form, it allows you to achieve any SPI finish on your tooling. Hard chrome is often a good choice for electrical circuitbreaker molds since they use materials containing as much as 40 percent glass. To help bat erosion and prevent severely damaging gates and surrounding mold areas, it is usually remend to use a highdiamond polish, followed by a hardchrome coating of to inches for added protection. The downside can be cost, since chrome plating is limited to areas accessible by an anode. If your mold has plex details, it could require extra conforming anode construction and that adds time and expense to the project. Another possible drawback is chrome’s environmental impact—chromium is a carcinogen. Some panies are attempting to develop better, cleaner alternatives, but so far nothing matches hard chrome’s benefits from a tooling perspective. Electroless Nickel Like hard chrome, electroless nickel has been used successfully for years, particularly to protect molds where corrosive offgassing is created by materials such as PVC or halogenated fire retardants. It is not unmon to see such resins produce an orange rust, corroding the unprotected mold almost right before your eyes. Products molded of such materials for the electronic or medical industry often cannot tolerate the presence of any oxidation byproducts. Electroless nickel does an excellent job of resisting oxidation because it plates very uniformly in thin deposits of to inches. Even in tight areas of detailed parts, electroless nickel at 50 RC hardness is ideal for corrosion protection. It can be deposited in very accurate thicknesses of to inches and can be ground or EDM’ed. Thus, electroless nickel often is used for dimensional buildups under flash chrome and for enlarging threaded cores and inserts or precisely sizing cavities. It also works very well on entire mold bases, A and B plates, ejectorbase housings, pin plates and pillar supports, providing years of lowmaintenance, rustfree operation. Know Your Mold Finishes Before determining what coating to use—if one is needed—the mold finish must be taken into account because, as noted earlier, certain finishes may actually increase the need for a mold coating, and some binations work extremely well together improving lubricity and release properties. There are four standard SPI finishes: diamond, stone, paper and blast. Each gives the molding surface a different appearance, from a glossy, mirrorlike surface (A1 Diamond) to a fairly rough, gritty texture (from blasting with glass beads or aluminum oxide). Each of the four finishes has three grades as well. Diamond The A1 Diamond finish is the most perfect finish available, which means it has the lowest RA value (roughness average). There are no high or low ridges. For example, a paper scratch on steel can rate a 2 to 4 RA finish, whereas an A1 Diamond is lensquality smoothness, generally 1 RA or less. Roughness is almost immeasurable. But a number of plastic materials tend to stick like glue to the flawless, mirrorlike finish, making such perfect smoothness almost detrimental in many molding applications. One good example is molding polystyrene on a polished straightwall core with 1d or less draft. Streak or drag lines can appear on the parts. This can be solved by flashchro。