This study aims to design a method for implementing the non-uniform rational B-spline (NURBS) curve fitting process on CNC machines for improving the machining quality and efficiency. The conventional CAD/CAM/CNC systems usually induce some machining problems and limit the machining results in real applications. An on-line NURBS curve fitting process consists of fetching and fitting stages is developed in this paper. The fetching stage fetches a block of NC code and extracts motion commands for obtaining data points. The fitting stage processes the NURBS curve fitting method with a given set of data points. Moreover, the optimal search method is designed for obtaining good NURBS curve fitting results. Simulations and machining tests on a vertical machining center show that the proposed approach reduces the machining time about 23% while maintains the machining quality for sample test.
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