MOTION SYSTEMS HANDBOOK
Gearbox
service factor and service class
explained
Sizing a gearbox (or gearmotor) for an industrial application typically begins with determining the appropriate service factor. In simple terms, the service factor is the ratio of the gearbox rated horsepower (or torque) to the application’s required horsepower (or torque). Service factors are defined by the American Gear Manufacturers Association (AGMA), based on the type of gearbox, the expected service duty, and the type of application.
While service factors may seem to be very specific, with thousands of combinations of gearbox types and applications each assigned its own numerical value, the criteria used to determine these values are based not on testing and empirical data, but rather on extensive review and analysis of gearbox manufacturers’ experience. In general, the horsepower (or torque) rating of a gear tooth is based on the durability of the gear surface — its resistance to pitting — or on its bending fatigue. As the service factor of a
Shown here is an animatronics design featuring a robolink from igus. The worm-gear assembly is complemented by strain-wave gearing elsewhere.
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DESIGN WORLD — MOTION
Gearing — Motion Control HB 08-19 V3.indd 78
8 • 2019
motioncontroltips.com | designworldonline.com
8/21/19 12:51 PM
