Wear and cost issues in magnetic fluid grinding

The grinding surface in magnetic fluid grinding (MFG) was originally created by embedding initially loose grits into a metal grinding shaft. Developments have included replacing the magnetic fluid by a cheaper, viscous, non-magnetic fluid, and loose grit/metal shafts by pre-manufactured resin-bonded or electro-plated diamond grinding surfaces. This paper reports grinding rates and grinding ratios, and diamond consumables process costs, for both the original and the resin-bonded or electro-plated grinding surface processes, for finish-grinding silicon nitride ceramic ball bearings. Grinding rate is reported as ball diameter reduction per unit time. Grinding ratio is the ratio of volume lost from the ground surface to volume lost from the grinding surface. In no case has a grinding ratio greater than 10 been achieved. In other tests, surface grinding the same grade of silicon nitride with peripheral grinding wheels of the same resin-bond, diamond type, size and concentration as in MFG, in conditions that cause similar grit loads as in MFG, grinding ratios have been achieved greater than 100.