The design of key aircraft components, such as frame, beam, wall and skin parts, is composed of a large number of pocket features, whose machining efficiency directly influences the overall machining efficiency of aircraft parts. The development of high speed milling machine has provided a good hardware foundation for highly efficient machining of such parts, but also poses new challenges to generation of tool path of pocket milling. For example, in mirror milling for aircraft skin parts, due to its special mechanical setup, stringent requirements of toolpath such as smoothness, no tool retraction and prescribed stepover variation are made to ensure high quality machining of skin parts. To maintain the high feed rate and spindle speed in high speed machining of structural parts, tool path should also be smooth and the stepover should vary smoothly. However, existing pocket milling tool path strategies are mostly based on local optimization to deal with defects of uncut region and unsmoothness, and are hard to satisfy multiple process constraints, especially the constraint of stepover, so it is hard to make full use of high-speed machine. To solve this problem, a tool path generation and optimization approach of pocket high speed milling based on medial transformation is proposed in this paper. In this method, the skeleton of pocket is extracted based on medial transformation, and the offset criterion of tool path and the initial tool path are generated by further modification. Then, the image deformation algorithm is used to perform iterative deformation optimization on the initial tool path, so that the final optimized tool path conforms to the target pocket machining region and the process constraints of high-speed machining are satisfied. This method optimizes the overall tool path in the discrete image domain. The experimental results show the method can ensure not only smoothness of tool path without tool retraction, but also gentle stepover variation in the allowable range, which meets the requirements of high-performance machining.
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