In-process diameter control in precision cylindrical grinding

INTRODUCTION This article shows the theory and implementation of a force measurement-based approach to controlling workpiece diameter in cylindrical grinding. A simple model proposed by Chen et al. is used to relate infeed velocity to grinding force. The model is extended here to accurately predict the amount of material removed in OD plunge grinding given the normal force, which may be monitored in real-time. The model gives rise to a time constant that is a function of the structural loop stiffness, the infeed velocity, and the wheel and workpiece properties. This time constant may be measured during grinding to characterize the lag between infeed and stock removal. Once determined, the removal of stock can be predicted using force feedback. This allows very accurate diameter control (0.25 μm of nominal), even in the presence of thermal drift, wheel wear, and machine error.