Error Analysis And Compensation For Large Automobile Plastic Mold Using High Speed Machining

Die and mould process technology with high-speed machining changes the mold manufacturing process, and improves the machining efficiency and quality of the die and mould. Studies at home and abroad mainly focus on the way of feed, tool paths, corner and residual analysis, however, the machining error and error compensation using high speed machining were seldom researched, correspondingly. This paper mainly researches the reasons of error and error compensation for large automobile plastic mold, predicts the value of the machining error, and makes compensation by off line, based on the characteristics of process error. This research has positive meaning for improving the quality and efficiency of large automobile plastic mold, meanwhile the manufacture of other mold and die can reference to it.In this study, the ball end milling of (?)6mm with coating, which commonly used in practice, is adopted to cut P20, a kind of wide using pre-hardened plastic mold steel. The main study includes the following.1. According to the cutting theory, the prediction formula of cutting force in finish milling with ball-end milling was developed, and specific and edge force coefficients was found by experiment. 2. The relationship between tool horizontal deflection and machining error was found. The quantity of tool horizontal deflection is measured and the machining error is predicted with the help of Finite Element Analysis software.3. In order to improve the accuracy and rapidity of Finite Element Analysis, the speciality of tool and tool-holder assembled is studied and simplified by experiment.4. The characteristics of cutting force and variation during high speed machining are studied through declined surface milling experiment which can be referenced to machining sculptured surface. The results show that the effects of ramping down milling are the best. setting optimization aim as cutting force and vibration, the best cutting parameters are achieved.5. Tool path error is discussed, which includes ball end milling process residual, additional error due to the offset of tool path, and linear approximation error, etc. the relationship of residual and ball radius, feed step are obtained in machining declined surface.6. The error is compensated off-line according to the predicted machining error through surface offset. Then NC Program is produced to cut the work-piece. Finally, this method has been validated through an example.