模具毕业设计--外文翻译.doc

How Surface Treatments Keep Molds Operating LongerImportant tips and information about mold coatings to help you achieve the level of production that you and your customers desire. By Steven . Bales Mold making technology January 2006AbstractTheres an awful lot to know these days about molding plastic and how to get the very best performance from the valuable tools you build or run. This guide has been written to provide important tips and information about mold coatings. After reading this, you should have a very good idea of what coatingsfrom the very traditional to the very latestwill help you to achieve the level of production you and your customers desire. After all, these tools are an investment and they need to be protected for the life of the products they mold.Key Wordsmold coatings preventive maintenance (PM) program benefit nickel Cobalt diamond-chrome nickel-PTFE nickel-boron nitride electroless nickel textureThe Key Role of CoatingsBefore introducing you to the wide range of coatings on the market today, its important to note the role coatings can play in an effective preventive maintenance (PM) program.PM is really the key to protecting your tooling, your investment. Why? Because it saves time and money. Once you invest in a mold coating to improve tool performance, then a PM program is always a good idea to ensure you get the maximum benefit. These two steps should be a given in any shop.Remember, no coating lasts forever, and producing substandard parts from a mold with a worn coating is no way to win customers and stay profitable. PM is probably the most cost-effective strategy you can put in place. The key is to educate your personnel on how mold coatings wear during production. Every coating is different, so its of benefit to have employees learn how to tell when the coating is showing deterioration, especially in high-wear areas such as gates and runners. For example, wear in and around gate areas plated with hard chrome is the first sign that your mold needs servicing. How can you tell there is wear? The chrome coating is approximately 20 RC points harder than the base steel, so exposed steel will wear much faster than the coated surfaces surrounding it, causing a slight or pronounced edge or “step” on the surface. Conversely, nickel will wear almost evenly, causing a kind of feathering effect, making it more difficult to recognize wear. A more identifiable difference will be the color because when nickel coating wears, it produces a shadow or halo effect on the steel. No step or edge will be evident. The steel also will have a more silver appearance compared to the somewhat tarnished look of the nickel coating.This knowledge makes pulling a mold for maintenance before the coating wears through an ultra important aspect of a PM program. To miss important wear signals means more costly repairs and additional polishing expense. Measuring WearA recommended tool for measuring the wear level of any coating is an electronic thickness gauge that uses a combination of magnetism and eddy current to accurately measure surface thickness. When the mold first arrives in your plant, take the time to measure the surface thicknessespecially in high-wear areasusing this specialized tool. As you run production on the mold, occasionally pause to re-measure those areas. When you have determined that the finish is wearing to a critical level, pull the mold and send it out for maintenance.Part CountsBe sure to record the measurements taken with the thickness gauge and use the notes to create a history of maintenance requirements for the tool. A cycle counter installed on the mold will allow your tooling engineer to record wear levels as compared to piece part counts, thereby doubling the effectiveness of your PM program. Part counts are a great way to determine maintenance needs, especially with high-volume molding projects.From the very first time you run the mold, keep an accurate piece count until it is ready for its first maintenance work. Use that count as a gauge for when the next maintenance is due. Because you know approximately when the mold will be ready to be refurbished, you can arrange the service in advance with your coating vendor. This not only gives him ample time to schedule your mold maintenance, but it also allows you to optimize the use of the mold and the machine thats running it.Coating ChallengesEven today, there are those who question the benefits of using fancysometimes more expensivecoatings to prolong tooling life or enhance performance. To some, the tried and true hard chrome or electroless nickel are all theyll ever need to accomplish those goals. But we all know that todays engineered plastic materials can be pretty rough on injection molds. Challenges to mold maintenance extend beyond glass- and mineral-fillers to include rice hulls, wood fibers, metal powders, flame retardants and other additivesnot to mention the resins themselves. In addition, outgassing and moisture acidity often accompany abrasive wear, taking an even bigger toll on expensive tooling.In addition, growing complexity in mold design involves tinier, more intricate flow passages and more frequent use of moving cores and slides. All of these circumstances have prompted the development of a wider variety of mold coatings that can keep molds operating longer between repairs.New Coating ScienceIf you are molding highly intricate parts using glass-filled materials, you might think using hard chrome will be sufficient because it is a classic, reliable way to protect your mold from both corrosion and abrasion. However, hard chrome, for all its benefits, does not tend to plate uniformly in detailed areas like ribs and bosses. There is a newer solutiona nickel-cobalt alloy coating that can overcome that limitation. Nickel CobaltNickel-cobalt can be an economical alternative to hard chrome. Hard chrome requires construction of a conforming anode to coat the mold. The more detail in the mold, the more time it takes to build the anode and the more expensive the process becomes. This nickel-cobalt alloy coating requires no anode, and because of its electroless properties, it plates much more uniformly. The cobalt gives it good abrasion resistance, but its hardness is 62 RC, 10 points lower than hard chrome. Is it worth paying extra for hard chromes superior wear protection? You have to consider the material being run in the mold. Whats the percentage of glass? Is corrosion a greater concern than abrasion?Diamond ChromeHard chrome and a nickel-cobalt alloy coating offer two very good solutions for abrasion resistance, but for very high-wear conditions, an even newer product called diamond-chrome offers exceptional protection. It has an RC rating greater than 85 and is a chromium-matrix composite coating with a dispersion of nanometer-size, spherical diamond particles. Since diamonds are unmatched for hardness, this coating offers protection beyond the norm. Though their Rockwell ratings are comparable, diamond-chrome outperforms titanium nitride (TiN) coating because it wont compromise the dimensional integrity of the plated tool. The difference is that it is applied at only about 130oF while TiN requires application temperatures of 800oF or higher.Diamond-chrome can plate prehardened, heat-treated or nitrided steel and other base materials such as aluminum, beryllium-copper, brass and stainless steel. Recommended uses include cores, cavities, slides, ejector sleeves, and rotating and unscrewing cores. Its anti-galling properties are advantageous on moving cores and slides.Diamond-chrome also is very strippable and has no adverse effect on the base material, saving time and money when maintenance is needed. TiN is strippable as well, but it can take up to several days to remove with a peroxide-based solution. Diamond-chrome can be stripped in minutes using reverse electrolysis in a caustic solution. In addition, diamond-chrome can be deposited at any controlled thickness from 20 millionths of an inch to 0.001 in. TiN is generally only applied in thin deposits of a few millionths of an inch. Diamond-chrome can coat complex details, while TiN has very limited coverage of complex details. While TiN is very lubricious, with a coefficient of friction (COF) of 0.4 (against steel), diamond-chrome has a COF of 0.15nearly three times more lubricious.Nickel-Boron NitrideWhen it comes to molders needs for a specialty coating that offers excellent release properties and high resistance to wear, heat, and corrosion, an electroless nickel-phosphorus matrix containing boron nitride particles should be considered.It has a very low COF (0.05 against steel) and an RC hardness of 54, which can be increased to 67 RC after heat treatinga unique characteristic. Nickel-boron nitride can be applied to any substrate at only 185oF and can be easily stripped without compromising the base material. Though it is approximately 20 percent more expensive than nickel-PTFE, this coating will outperform nickel-PTFE at up to 1250oF, which far surpasses the 500oF maximum limit for all PTFE-based coatings.Because applying nickel-boron nitride is an autocatalytic process, it requires no anode, therefore saving time and money. In addition, it will not compromise 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, zero-draft cores, textured surfaces and “sticky” polymers, a nickel-PTFE composite will greatly improve part release and enhance resin flow by as much as 4 to 8 percent for shorter cycle times. COF is 0.10 against steel.It should be noted that applying pure PTFE to the mold adds high lubricity, but only a very short-term benefit. PTFE by itself has no hardness, so it wont last. But a dispersion of 25 percent PTFE by volume in a co-deposit with nickel results in 45 RC hardness for added wear and corrosion protection.Tried and TrueDespite the new coating science, we cannot throw out the old, reliable coatings such as like hard chrome or electroless nickel just yet. Theres no question that they still have their uses. Hard ChromeFor example, hard chromes 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 circuit-breaker molds since they use materials containing as much as 40 percent glass. To help combat erosion and prevent severely damaging gates and surrounding mold areas, it is usually recommend to use a high-diamond polish, followed by a hard-chrome coating of 0.0003 to 0.0005 inches for added protection.The downside can be cost, since chrome plating is limited to areas accessible by an anode. If your mold has complex details, it could require extra conforming anode construction and that adds time and expense to the project. Another possible drawback is chromes environmental impactchromium is a carcinogen. Some companies are attempting to develop better, cleaner alternatives, but so far nothing matches hard chromes benefits from a tooling perspective.Electroless NickelLike hard chrome, electroless nickel has been used successfully for years, particularly to protect molds where corrosive off-gassing is created by materials such as PVC or halogenated fire retardants. It is not uncommon 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 0.0002 to 0.0003 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 0.002 to 0.003 inches and can be ground or EDMed. Thus, electroless nickel often is used for dimensional build-ups 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, ejector-base housings, pin plates and pillar supports, providing years of low-maintenance, rust-free operation.Know Your Mold FinishesBefore determining what coating to useif one is neededthe mold finish must be taken into account because, as noted earlier, certain finishes may actually increase the need for a mold coating, and some combinations 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, mirror-like surface (A-1 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.DiamondThe A-1 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 A-1 Diamond is lens-quality smoothness, generally 1 RA or less. Roughness is almost immeasurable.But a number of plastic materials tend to stick like glue to the flawless, mirror-like finish, making such perfect smoothness almost detrimental in many molding applications. One good example is molding polystyrene on a polished straight-wall core with 1d or less draft. Streak or drag lines can appear on the parts. This can be solved by flash-chrome plating the core, which creates a surface with micro-cracks. Impregnating those cracks with PTFE and then re-establishing the A-1 Diamond finish solves the problem in more than 95 percent of cases.In thin-wall molding applications such as these, a light bead-blast finish is appliedjust enough to very slightly interrupt the flawless A-2 Diamond surface. The surface is buffed again, leaving just a bit of almost invisible stipple. This finish plus a coating of nickel-PTFE will greatly improve part release and enhance mold filling.Phenolics and other thermosets almost demand a perfect polish and work extraordinarily well with a diamond finish. Combine that with a hard, protective coating like chrome or diamond-chrome, and you will strengthen the molds surface and optimize release. Phenolics and other thermosets almost demand a perfect polish and work extraordinarily well with a diamond finish. Combine that with a hard, protective coating like chrome or diamond-chrome, and you will strengthen the molds surface and optimize release. Texture and ReleaseThere are many textured surfaces today, including faux leather for automobile dashboards, wood grains, geometric patterns and stipple patterns found on pagers, cell phones and computer components. A plated mold coating is often essential to obtaining a textured surface with adequate lubricity.Textured surfaces require protection. The peaks of the textured surfaces are the first areas of mold detail to experience wear, making it very important to check the mold periodically with a profilometer to measure grain depth and peak counts. Mold coatings help decrease the frequency of repairs and refurbishment by maintaining the integrity of the textured surface.If a diamond finish presents release problems, a blast finish can be the answerparticularly when molding textured parts using materials such as silicone rubber, flexible PVC, TPES and some soft polypropylenes. These products tend to cling to a polished finish, but breaking up the surface with a light blasting improves release. Add a coating of nickel-PTFE and you get even better release.Hard chrome and electroless nickel plating will help protect textured surfaces, as will a nickel-cobalt coating. Unlike hard chrome, electreless nickel-cobalt plates uniformly, which makes it ideal for very detailed molds with deep ribs and bosses. It combines the corrosion protection and lubricity of electroless nickel with the strength of cobalt.SummaryIf youre looking for enhanced performance in your molds, the proper combination of surface treatment and finish can provide additional benefit by extending production times between preventive maintenance. Your coatings vendor can be a valuable resource for educating your personnel on how coatings you use will wear over time, as well as a way to reduce downtime and cut costs. 46 译文标题表面处理如何延长模具运行周期原文标题How Surface Treatments Keep Molds Operating Longer作 者Steven . Bales译 名史蒂芬.巴莱斯国 籍美国原文出处Mold making technology January 2006有关于模具涂层的重要提示和信息，有助于您达到满足自己及客户需求的产品标准。（史蒂芬.巴莱斯）摘 要现今对于成型塑料及如何获得所操作的贵重机床的最好性能，已经有了极多的了解。该指南就模具涂层提供了重要的提示和信息。阅读后，你应该对使用何种涂层有助于获得满足自己及用户要求的产品标准，无论是选择传统还是最先进的涂层。毕竟，这些模具是你的投资，它们需要保护，以获得高的成型制品的使用期。关键词：模具涂层 预防性维护（PM） 效益 镍钴 钻石铬 镍-聚四氟乙烯镀层 硬铬 聚四氟乙烯 镍氮化硼 电镀镍 纹理涂料的关键作用在向你介绍涂料在当今市场上广泛应用前，你要注意到涂层的作用在模具预防性维护（PM）方面起了相当有效的作用。模具预防性维护技术在保护你的模具和投资起着关键的作用，因为它节省了你的时间和金钱。一旦在模具涂层方面投资以改善模具的性能，模具预防性维修技术总是一个很好的选择来保障你获得最大的效益。这种技术是应该应用在每家生产单位的。也请记得没有什么涂料可以永久使用，一个表面磨损的模具上生产出的标准零件也是无法赢得客户信任和保障自己利益的，但模具预防性维修技术是个使用到位时最具成本效益的方法，它可以告诉工作人员在生产过程中涂层的磨损状况。各种涂层是不同的，它有助于让员工了解涂层何时出现恶化，尤其是在高速运转强磨损情况下比如出现镀层穿孔的情况。例如模具硬铬镀层穿孔周围出现磨损是表示你需要对模具维护的一个迹象，你怎么区分有没有磨损？因为硬铬涂层要比普通钢硬大概20个洛氏硬度，因此裸露的钢基磨损的速度比有涂层的钢快，造成表面细微或者明显的边界。而镀镍层会使模具表面形成几乎均匀的一种羽化效果，使其更加难以辨认磨损区域。唯一较明显的差异是色彩，因为当镍层磨损，它产生了关于钢铁的阴影或光环效应。之前再没有其他明显的迹象，而且出现这种情况的钢，相比那些有镍镀层的无光泽的钢还显得更加亮。这些了解使在涂层磨损前对模具的维护成为PM计划的一个重要方面。如果错过重要的模具磨损信息，就意味着将来更多的高昂的维修费用和额外的抛光费用。测量磨损一种被推荐的测量涂层磨损程度的工具便是电子测厚仪，它使用磁涡流相结合，以准确测量表面厚度。当一种新模具首次到你工厂时，花时间去测量表面厚度，特别是在高耐磨区常使用这个专门的工具。当运行新模具进行生产时，也要偶尔停下来重新测量这些区域。当你确定镀层已经磨损到临界水平，把模具取出