Gear Production

SEP 2016

Gear Production

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September 2016—9 coating on gears and similar components. This makes it possible to develop level surfaces with micro-finish surface attributes. This technology is especially applicable to automotive gear train systems and engine components such as camshafts and crankshafts, and is widely seen among racing teams to acquire performance advantages. Centrifugal Barrel Finishing—This high- energy method is a mechanically accelerated means for producing edge contour and isotropic micro-finishes on gears. This method is used by a variety of gear manufacturers and high- performance racing teams to improve the surface finish and endurance of gear sets. It is also capable of producing low micro-inch finishes to improve load-bearing qualities of mating surfaces and to develop beneficial compressive stress and cold-hardening properties useful to highly stressed parts. A sequence of processes (analogous to roughing, finishing and polishing) is often used to develop highly finished surfaces. The high centrifugal forces and speed of this process achieve high-level surface finishes in short cycle times. One user, Mr. Davidson recalls, pulled racing transmissions after each event for centrifugal finishing, only to find afterward that gear sets were lasting an entire season. A note here about isotropic surface finishes for gears. Isotropic finishing, Mr. Davidson says, is a technical term used to distinguish surface finish patterns that are random and non-directional in nature. "This is in contrast to surfaces developed by all common machining and grinding methods, characterized by Gaussian peak-and-valley distributions parallel to each other that manifest a positive skewed surface with surface peaks and asperities predominating the surface profile," he says. By this definition, all mass finishing methods could be said to be isotropic in nature. The process outlined above, however, has been optimized to consistently produce gear surface finishes that will improve overall operational performance and extend service life. Turbo-Finish or Turbo-Abrasive Machining— This is the next-generation gear-finishing method, according to Mr. Davidson, who advises and assists Turbo Finish Corp. of Barre, Massachusetts, developer of turbo-abrasive machining (TAM). Not wholly machining and not wholly finishing, one of the properties separating TAM from vibratory or centrifugal gear finishing is that it is a dry method using no fluid media. Parts are fixtured on a spindle, similar to a horizontal Gear before (top) and after (bottom) turbo abrasive machining (TAM). (Photo courtesy of Michael Massarsky, Turbo Finish Corp.)

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