Five-axis contour error control considering milling force effects for CNC machine tools

Abstract

In order to improve the quality of five-axis machining, the effects of milling force in feed drives have to be considered comprehensively so as to obtain better dynamic performance. In this paper, a model of five-axis machine tool feed system is established to analyze the influence of milling force on the feed drive dynamic performance. The equivalent disturbance on each axis is deduced based on the instantaneous milling force model. A cutting force model has been provided from Tool Coordinate System to Machine Coordinate System for disturbance estimation in each feed drives of five-axis machine tool. The cutting force on the workpiece is transformed to the load torque on each motor through the estimation matrix. Therefore, a control strategy of the five-axis contour error caused by milling force is proposed. Both the contour error and tool orientation error are pre-compensated based on the dynamic of the feed drives. Finally machining experiment was performed to verify the high accuracy of equivalent milling disturbance estimation. The result also proves that the five-axis contour error caused by milling force can be greatly reduced through the contour error compensation. It provides a practical application in high-quality five-axis machining.