Optimal pitch angles determination of ball-end cutter for improving five-axis milling stability

Abstract

Regenerative chatter is one of the major limitations in five-axis ball-end milling of complex shaped parts, resulting in reduced productivity and poor quality. Although a good solution can be provided for the chatter avoidance and the stability enhancement by using variable pitch cutters, it depends on the optimal selection of pitch angles, and few studies focus on determining the optimal pitch angles combination for the five-axis ball-end milling process in a continuous spindle speed range. In this paper, the pitch angle optimization is based on the fast and accurate stability prediction of five-axis ball-end milling with variable pitch tools. Considering that the search space of the stability border should be reduced as much as possible during the optimization process, an approach combining an improved hybrid multi-step method and an optimization strategy of stable area maximum is presented for efficiently finding the optimal pitch angles. For selected spindle speed ranges and given lead/tilt angles, the optimal pitch angles of variable pitch ball-end cutter are determined with the proposed optimization approach. The experimental results show the average stability of the customized optimal variable pitch ball-end cutter is significantly higher than that of the regular ball-end cutter, validating the proposed optimal pitch angles determination method. Compared with the semi-discretization method, the use of improved hybrid multi-step method for predicting the stability border reduces the simulation time by around 84 %. In contrast to the optimization strategy based on the average characteristic multiplier, the proposed optimization strategy is more efficient because it does not require a large number of characteristic multipliers.