A new approach to form accuracy control in machining

In the past considerable know-how has been generated with respect to dimensional accuracy and the surface finish of machined workpieces, however, efficient methods are lacking for the improvement of the geometrical form generating capabilities of machine tools. In this paper a forecasting compensatory control scheme for the reduction of form errors in machining is presented. The approach considerably departs from traditional methods since it does not require a high precision machine tool for the achievement of high precision results. The basic underlying idea is to make use of advances in computer. sensor and actuator technologies in connection with on-line system identification methods, to implement a forecasting compensatory controller. The error motion component signals are sensed on-line by a microcomputer which develops a stochastic difference equation of error motion which in turn is used to forecast the future relative, displacement between tool and workpiece forming the basis for a proper compensatory action. The feasibility of the method is demonstrated on examples of roundness and straightness control in grinding and milling respectively.