Research On Feedrate Optimization For Mould Cavity Machining Based On Instantaneous Milling Force Model

Die & Mould is the basic technical equipment for industrial manufacturing. High accuracy, short manufacturing cycle and lower cost are its necessary developing direction. So digitized manufacturing technology must be widely used in Die & Mould industry in order to shorten the manufacturing cycle. As a significant machining means of mould, NC machining is one of the most important factors which influences the mould manufacturing cycle and quality. Further more, NC machining of mould cavity is the most difficult and time-consuming part. But the traditional NC machining always adopts a constant, conservative feedrate, which results in a very low machining efficiency. Therefore, how to improve the NC machining efficiency of mould cavity without losing machining quality has become an urgent problem to be solved.This paper researches on the optimization of NC machining feedrate based on the milling force prediction model of the ball-end mill which is popular in NC machining of mould cavity. The main research contents are as follows:According to the Z-Map model for workpiece and the discrete points model for cutter and the dynamic track of ball-end mills, an algorithm for micro-geometric simulation of sculptured surface machining with ball-end mill is presented. The micro-geometric simulation provides the precise profile of the chip, which becomes the most important geometric parameter for subsequent milling force prediction.Based on the micro-geometric simulation, a milling force prediction model for ball-end mill considering ploughing force and shearing force is presented. The ploughing coefficients and the shearing coefficients are regressed from orthogonal cutting tests. Then the instantaneous milling force can be predicted by inputting the geometric parameters from geometric simulation to the milling force prediction model.According to the instantaneous milling force from the milling force prediction model, the relevant federates on different cutter-location points are evaluated by its cutting load. Then the cutter-location points are divided into pieces due to close feedrates. The lowest feedrates of each piece are adopted and rounded up to be the whole piece's feedrates. Finally, an efficient and rational NC program can be gained by rewriting the optimized feedrates back to the original NC program.Experiments have proved that the feedrate optimization means presented in this paper is efficient and rational, which effectively improves the NC machining efficiency of mould cavity without losing machining quality.