High Speed, Automatable Superfinishing of Rear-Axle Hypoid Gears 2012-01-0164

The benefits gained by superfinishing rear-axle hypoid gearsets are now well documented. Friction, wear and operating temperature are significantly reduced. The main impediment to commercially implementing this process, however, is that it increases manufacturing cost in terms of process speed, work in process and labor. The cost of superfinishing can be significantly reduced by employing a newly developed and fully automatable drag finishing process.

The most primitive form of drag finishing occurred when Roman soldiers dragged their armor through sandy fields for obtaining a mirror-like appearance. Today's drag finisher, of course, is much more sophisticated. A circular turret is located above a circular bowl containing loose, ceramic media. Parts are attached to multiple rotating spindles on the turret, which in turn are immersed in the media in the bowl below, and are dragged through the media. This generates a high flow of media over the gearsets. By a judicious choice of media and a chemical accelerator, the hypoid gearsets can be superfinished in less than five minutes to an R_a of less than 0.15µm, while maintaining gear geometry. The turret speed, spindle speed and direction of rotation and depth in the media are controlled with a programmable logic controller. The angle of the spindle can also be adjusted. A novel fixture has been developed that adds quick change capability of gearsets (a matter of seconds), and facilitates automation.