B-spline smooth compression of consecutive micro segment trajectories in free-form surface NC machining

In NC machining of free-form surfaces, low efficiency, unstable machining process and poor quality of the finishing surface occur frequently for the usage of numerous micro segment trajectories. To address these challenges, a B-spline smooth compression (BSC) algorithm of consecutive micro segment trajectories (CMSTs) is proposed. In this algorithm, CMSTs are first extracted according to geometric features of the trajectories. Then each CMST is separated into convex hulls based on its inflection points obtained from the curvature of cutter locations (CLs). Finally a least squares fitting (LSF) method considering the endpoint and the tangential vector constraints is applied to transfer each convex hull into B-spline. The target B-spline can be obtained by increasing the control points in the fitting process if the fitting error exceeds the given value. Simulations show that the proposed algorithm is superior in aspect of computational efficiency and code compression ratio. Moreover, comparing with micro segment trajectories, B-spline trajectories generated by BSC has higher machining productivity and surface accuracy.