Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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mechanical surface preparation Everything You Need to Know About Mechanical/Mass Finishing BY EUGEN HOLZKNECHT, RÖSLER METAL FINISHING USA, BATTLE CREEK, MICH. Mechanical surface finishing, also known as mass finishing or vibratory finish- ing, is a surface finishing technology that has been around for more than six decades. At the time it was invented in the 1940s, mechanical surface finishing revolutionized whole industries with regard to their surface finishing meth- ods. Large international companies like Volkswagen and Mercedes-Benz in Germany were literally queuing up to initially get a hold of rotary barrels and, lat- er on, the first mass finishing vibrators. Delivery times of 24 months or more were not unusual. Deburring previously was a purely manual operation with extremely high personnel costs, poor quality, and no consistency or repeatability of results. Then, all of a sudden, manual finishing operations could be replaced with a mechanical process that significantly reduced personnel costs but, more impor- tantly, one that consistently produced higher-quality parts with a high degree of repeatable results. SOPHISTICATED SUPERFINISHING OF HIGH-VALUE COMPONENTS Over the years, mechanical surface finishing has evolved from a simple deburring method into a sophisticated technology covering a broad range of industries and applications. Here are just a few examples of "high-tech" mechanical finishing applications: • Grinding and polishing of medical implants, such as artificial knees, hips, ankles, etc. In the medical implant industry, special mass finishing processes have been replacing robotic grinding and buffing systems (Fig. 1). • Superfinishing of automotive gears down to a surface roughness of <2 (0.05 µm) to increase the life of power trains, reduce running noise and, at times of high fuel cost, reduce the weight of these components without jeopardizing their reliability (Fig. 2). • Surface finishing of aero-engine components, such as turbine blades, blisks, turbine disks, vanes, etc. In combination with shot peening, mass finishing processes reduce the "maximum exhaust gas temperature" (MEGT) and increase the time intervals between engine overhauls. Better surface finishing of turbine blades also increases the acceleration and compression of the air mass flow in turbines, resulting in lower fuel consumption—an invaluable technical benefit with today's high cost of kerosene (Fig. 3). Unfortunately, mechanical surface finishing is a largely empirical process and, for this reason, it is one of the least understood and appreciated manufac- turing technologies. The intention of this article is to provide a better understanding of mechan- ical surface finishing with particular emphasis on the role of the finishing 11

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