Improvement of the Appearance of Machined Surface by Modification of Tool Center Points in Ball-End Milling

In dies and molds machining, high surface quality is necessary to manufacture current industrial products. Free-form surfaces of die and mold are usually machined using reciprocating tool paths with a ball-end mill. However, position error of tool center points may occur in the tool paths generated by using a computer-aided manufacturing (CAM) software. Because the position error causes a lack of uniformity of the machined surface, the tool center points are modified by skillful operators to achieve high surface appearance. Therefore, a modification method to correct the position error is devised to automate the manual modification in this study. In the method, sensitivity is defined as the index to quantify the influence of position error on uniformity of the machined surface. The tool center point having the position error is detected by introducing the thresholds based on the sensitivity and an appearance indicator that is the degree of non-uniformity of the machined surface. Then, the coordinates of the tool center point are automatically compensated to satisfy the targeted appearance. Simulation results confirm that the indicator meets the targeted value by the modification. Finally, the machining experiments demonstrate that the proposed modification method can be used to improve surface appearance.