Design and Application of a CNC Rotary Axis for Grinding Research

Abstract

This thesis presents four studies into cylindrical plunge grinding that used a custom built, instrumented rotary axis. The design and capabilities of the rotary axis are presented. These capabilities include accurate speed control and in-process force measurement. The rotary axis enabled research into workpiece stiffness, which show a 2.5 fold decrease in the effective stiffness from a 1" (25.4 mm) change in grinding location. The wheel wear of grooved wheels is also shown to be higher than the wear of non-grooved wheels. A method of optimizing material removal through force curve inspection was presented and found to be effective at reducing wear. The largest study compared the performance of grooved and non-grooved wheels in plunge grinding. It was found that grooved wheels lowered grinding forces, spindle power, specific energy, and the time constants. However, there was an increase in surface roughness and no measurable change in workpiece roundness. The final study looked at the effect of angular speed ratios on plunge grinding with grooved wheels. There was an observed texture at integer speed ratios and a variation of the grinding forces, power, and surface roughness at non-integer speed ratios. A formula was presented that can predict the texture of a circumferentially grooved wheel and may be used to explain the other process variations.