Electrolytic In-Process Dressing Superfinishing of Spherical Bearings Using Metal—Resin Bond Ultra-Fine CBN Wheels

Abstract

The use of electrolytic in-process dressing (ELID) superfinishing has been investigated with the aim of substantially improving surface finish on spherical bearing balls as well as reducing process times. Using ELID in a superfinishing configuration is substantially different from the more conventional precision grinding set-up. With this ELID superfinishing system, metal—resin bonded (MRB) wheels containing very small superabrasives (30 to 0.12 μm) were employed. Surface finishes of 2 nm Ra were achieved with a #12 000 wheel, an order of magnitude better than balls produced using the conventional production techniques of barrelling or polishing. Consistently sub-10 nm Ra finishes were achieved with a #2000 wheel. Different ways of using the ELID system, including ELID 1, ELID 2, and ELID 3, were studied to examine how the different types control the cutting condition at the wheel's surface. It is the ability to control easily the cutting condition of superabrasives of this size that allows mirror surface finishes to be efficiently produced. Monitoring of wheel spindle and ELID power usage was found to provide useful information in assessing the wheel condition.