Investigation of the Effect of Speed Ratio on Workpiece Surface Topography in Cylindrical Plunge Grinding using Grooved and Non-Grooved Grinding Wheels

Abstract

This work explores the effect of integer and non-integer speed ratios on surface topography in cylindrical plunge grinding with grooved and non-grooved grinding wheels. For this investigation, an extensive experimental study was performed along with computer simulations. This research started with the development of stochastic wheel models to carry out 2D cylindrical grinding simulations. The simulator provided an excellent prediction of surface roughness trends and insights into the underlying mechanisms that govern the resulting surface roughness. Next, all the integer speed ratios from 2 to 7 were used in both experiments and simulations to study the workpiece topographies. Integer speed ratios were found to produce higher workpiece surface roughness values compared to non-integer speed ratios, and thread-like patterns were observed for grooved-wheel grinding. A dwell time study was conducted which revealed that the surface roughness improved for dwell times up to 10 seconds for both grooved and non-grooved wheels. Therefore, the final set of experiments and simulations used 10 seconds of dwell time with non-integer speed ratios between 4 and 5. The experiments also found that grooved grinding wheels consume less energy and exhibit less process forces than the non-grooved wheels. Roughness peaks were found to occur in the workpiece surface because of a synchronization phenomenon that can occur between the cutting edges on the grinding wheel and the workpiece. Formulae to determine the minimum number of grinding wheel revolutions required for synchronization at different speed ratios were derived using a kinematical approach. These formulae were used to help predict optimal speed ratios. It was found that a speed ratio of 4.78 yielded the best surface finish of 0.302 μm for grooved-wheel grinding, while a speed ratio of 4.22 produced the best surface finish of 0.189 μm for non-grooved-wheel grinding. Although the grooved wheels yielded a rougher workpiece surface than the non-grooved wheels, grooved-wheel grinding using the optimal speed ratio was able to achieve close to the 0.30 μm “fine quality” surface finish standard. An important key takeaway from the work of this thesis is that grooved wheels have potential to further improve the surface finish if speed ratios with a higher number of grinding wheel revolutions for synchronization are selected and successfully achieved.