Conversion method study from cutter-location points to nonuniform rational B-spline toolpath NC file for high-speed machining

Abstract

Parts with complex curved surfaces are widely applied and the demands for the machining quality and the machining efficiency of such complex parts become increasingly higher. In order to realize high-speed and high-quality machining, the nonuniform rational B-spline interpolator is widely researched and demonstrated to be superior to the conventional linear or circular interpolators. However, the nonuniform rational B-spline toolpath NC files cannot be directly generated from the computer-aided design (CAD) models by using commercial computer-aided manufacturing (CAM) software. To deal with this problem, a conversion method from the cutter-location points to the nonuniform rational B-spline toolpath numerical control (NC) file is presented. To avoid the bad curve-fitting effect at sharp corners of the toolpath and to meanwhile reduce the computational burden, the cutter-location pre-processing method, consisting data segmentation and data simplification, is provided first. Then, the least-square method is employed to fit the cutter locations to the nonuniform rational B-spline curves, and an iterative fitting approach is proposed for linear/nonuniform rational B-spline hybrid toolpath generation. Finally, a user interface is designed for displaying the fitting results and outputting the NC file with nonuniform rational B-spline toolpaths. By using this method, nonuniform rational B-spline and linear toolpaths hybrid interpolation NC program can be generated for the high-speed machining of complex curved surface parts with the utilization of the nonuniform rational B-spline interpolator. The experimental results demonstrate the feasibility and the advantages of the presented method.