Research On The Optimazation Of Milling Process Of Automobile Panel Dies

Automobile panel dies are one of the most important process equipments in the automobile production. Two thirds of the developing cycle are the design and manufacturing, which greatly limit the time to market. Automobile panel dies in the manufacturing process, due to the dies with high hardness, high precision, are usually used relatively conservative techniques to complete, which will inevitably lead to reducing machining efficiency and precision. This thesis aimed to actual demand for dies of automobile panel dies in production and processing,the goal was to improve the milling production and processing accuracy. In the die milling process oriented, this thesis used the method of off-line optimization and launched the research from three aspects: the cutting tool, trajectory planning and process parameters optimization. The specific contents include:A study of the regional division of the die surface based on the surface feature was proposed. Based on a description of the mathematics and the analysis of geometric characteristics of the die curved surface, the die surface was divided roughly. The die surface was exactly divided with the method of K-means clustering algorithm, and the boundary was extracted with the perpendicular bisector. It provides the research basis for the following optimization of cutting edge type of milling tools and the tool path planning of surface milling.A high efficiency machining of the die surface based on the optimization of the cutter structure was proposed. The disadvantages of conventional rounded end mill in rough machining of the die surface are analyzed, and a different structure of rounded end mill was presented. The geometrical relationship between the scallop height and the parameters of the new rounded end mill was analyzed quantitatively. The effect of structural parameters of the mill on cutting performance was carried out. The results showed that the cutting performance of the new rounded end mill is better than the conventional one.The tool path planning of die machining based on load control was proposed.The model of the milling force was established to apply for the die surface machining, and the force map of the surface was constructed. The problems of tool path planning were classified to the traveling salesman problem(TSP), the milling force effects were taken into account in the tool path planning of the die surface to achieve the stable loads in the process.Prediction of milling forces in machining corner of dies was established.According to the different contact between cutter and workpiece in the die corner milling process, corner milling process was divided into five parts, and instantaneous cutting thickness model was established for different stages of corner milling. The simulation results based on Matlab showed that the forecasted results were closer to the actual ones.The feedrate optimization for corner milling with multi constraints was proposed. Based on the establishment of instantaneous cutting thickness model in corner milling process, which was aforementioned, relative volume, milling force and cutter deformation were seen as control parameters to optimize feedrate of the corner milling respectively. Considering the machining efficiency and stability as the goal, feedrate during corner milling was optimized by combining with three control parameters, then the acceleration limits of the machine tool were considered in the optimization process to meet the requirements of practical production.