In-process Identification of System Time Constant for the Adaptive Control of Grinding

Abstract

The forces generated during the grinding process cause deflections of the machine-grinding wheel-workpiece system which are large compared to the accuracies required. The deflections cannot be precisely predicted and the optimum grinding conditions vary because the grinding wheel sharpness changes with grinding wheel wear and dressing. In practice conservative machining conditions and feed cycles are used in order to maintain the quality of the finished workpieces. This paper presents a new method of characterizing the time constant of the system from the grinding power consumption during the infeed section of a grinding cycle. Adaptive grinding cycles have been implemented which use the measured value of system time constant to control the target axis position and the dwell time. In this way the control system adapts the machining cycle for the wheel condition at the time of grinding, and can cope with the large variations in deflection that occur when using high feedrates.