Global toolpath modulation-based contour error pre-compensation for multi-axis CNC machining

Contour error compensation is an active research topic in five-axis CNC machining, especially in the manufacturing of sculptured surface parts. Nevertheless, current methods are mainly based on the mirror compensation principle, and fail to obtain a desired level of accuracy when processing parts with tight curvature feature. To address this issue, a global toolpath modulation-based contour error pre-compensation method is developed in this paper, which incorporates the error compensation issue into the stage of toolpath planning with a linear analytical solution. In this method, the nominal toolpaths used to machine the products is first expressed by dual B-spline curves, and then the instantaneous tracking error model of each individual drive is built with respect to control points of splined path. Afterward, the satisfaction condition of the spline control points for eliminating the contour error is yielded, which provides a possibility for compensating contour error in a global manner, and the neighbor-dependent coupling issue in error compensation between adjacent cutter location points is capable of being handled as well. On this basis, by applying the least-squares technique, the complicated contour error pre-compensation problem is further converted into a solution of simpler linear equation system. For enhancing its robustness when processing long toolpaths, an adaptive piecewise modulation strategy is also developed. Finally, both experiment and simulation are conducted to validate the proposed method, and the results demonstrate that the proposed method can significantly improve contour precision at low computational costs when compared with the existing pre-compensation method.

Automated summary

This paper proposes a global toolpath modulation-based contour error pre-compensation method for five-axis CNC machining. By incorporating the error compensation issue into the toolpath planning stage, a linear analytical solution is provided to solve the problem of insufficient accuracy in processing parts with tight curvature feature. The method utilizes dual B-spline curves to represent the nominal toolpaths and builds an error model for each individual drive. The satisfaction condition of the spline control points is obtained to eliminate the contour error, and the neighbor-dependent coupling issue in error compensation is addressed. The complicated contour error pre-compensation problem is converted into a solution of simpler linear equation system using the least-squares technique, and an adaptive piecewise modulation strategy is developed for processing long toolpaths. Experimental and simulation results demonstrate the effectiveness and efficiency of the proposed method in improving contour precision.