Local tool path smoothing based on symmetrical NURBS transition curve with look ahead optimal method: experimental and analytical study

[摘要] Linear tool path with the inherent shortcoming of tangential and curvature discontinuities leads to poor machining efficiency and surface finish. A lot of local corner smoothing methods which inset a tiny spline curve at the corners have been proposed in literature. However, there exists potential overlap of the two adjacent spline curves while smoothing, and still no optimal solution to fully use the segment length of each corner while eliminating the overlaps. To optimally eliminate the overlaps and smooth the transition curve curvature in real time, a symmetrical non-uniform rational B-spline (NURBS) curve transition based on look ahead optimal method is proposed in this paper, by scanning a set of unconstrained pre-cornering transition curve information, analysing the overlap type and backward determining the optimal transition length with curvature extreme smoothness in consideration, thus fully use the linear segment length of each corner and fully increasing the feedrate at the corners. G2 continuity, analytical expression of the curvature extreme, approximation error constraint, and real-time performance are considered simultaneously in this paper. Simulation and real machining experiments are made to compare with the existing symmetrical rounding algorithms, the results show that the proposed method has a significant curvature decrease of 17.64% and 4.44% improvement of efficiency, and the curvature distribution of the adjacent curves are balanced, thus improved the machining velocity smoothness. In addition, the real machining experiment results validate the proposed method can work well in 125 mu s real-time control period CNC system.

[效力级别]  Early Access

[关键词] CORNER;ALGORITHM