Research On Tool Path Optimization Method Of Flank Milling Undevelopable Ruled Surface

With the wide application of complex surface parts,Undevelopable ruled surfaces are also receiving more and more attention.Five-axis flank milling is an effective way to machine undevelopable ruled surface,while the principle error inevitably occurs.Therefore,it is important to plan the tool path to reduce the principle error.This paper proposes a new tool path planning method by studying the geometrical and machining characteristics of undevelopable ruled surface.The geometrical and machining characteristics of undevelopable ruled surface were studied.The generation mechanism of twist angle and the principle error during the machining process was analyzed.The empirical formula for the principle error of flank milling undevelopable ruled surface was obtained.Two methods for distance calculation,particle swarm optimization and surface subdivision,were studied to evaluate the tool path trajectory.A new local optimization method of tool path was proposed.First,an arc-shaped range,constructed by the twist angle and the radius of cutter,was built as the initial position of the tool shaft.Second,the circular arc was divided into several points,whose number is determined by the value of empirical formula for the principle error.Third,the proper tool position was selected based on the error propagation principle.Finally,the tool position was further optimized by the least squares method.The tool path after optimization was obtained by plus the tool center position.A new global optimization method of tool path was proposed by applying surface fitting theory based on sequential quadratic programming algorithm.First,the envelope surface of initial tool path trajectory was obtained.Second,some sampling points and its corresponding points on the design surface were obtained.Third,the two sets of point,representing the two surfaces,were optimized by sequential quadratic programming algorithm.Finally,the optimization result was transferred to the spatial transformation matrix used for the tool path trajectory.The optimized tool path and error distribution were generated by spatially transforming the initial tool path and the envelope surface.Three experiments were conducted to verity the effective of proposed method.The local optimization method was verified by comparing with the three points offset method.For the global optimization method,the optimization was compared between the least squares method and proposed method,which revealed the efficiency and accuracy of proposed method.Finally,a simulation experiment and processing experiment of “S” part was conducted to verify the proposed method.The results reveal the accuracy and feasibility of proposed method.