(B.6)Corner trajectory smoothing with asymmetrical transition profile for CNC machine tools. (September 2019) - Wang, Weixin
Abstract: The linear toolpaths, so-called G01 blocks, are widely used in CNC machining. Since this non-smooth path only achieves position continuity at the corner junction, it is prone to cause speed fluctuations and excite structural vibrations, which is not conducive to high-speed and high-accuracy machining. To solve the problem, typical corner smoothing methods generate a symmetrical cornering transition profile around the angle bisector, while respecting the given error tolerance. In this paper, a one-step corner smoothing approach with asymmetrical transition profile and limited jerk was proposed. The proposed approach can attain high reproducibility to guarantee good surface finish in back-and-forth parallel raster toolpaths, and is different from two-step corner path smoothing approaches which geometrically replace the sharp corner with a pre-specified curve. The near time-optimal transition parameters are obtained in one step, subject to the geometric error tolerance and kinematic limits. Since the proposed approach does not require a symmetrical cornering profile, the performance of the drives can be utilized more fully to obtain better cycle time than other approaches. Experimental results demonstrate the effectiveness of the proposed method on cycle time and contour accuracy. Highlights: Asymmetrical corner trajectory smoothing method with high reproducibility in back-and-forth parallel raster toolpaths. No need to blend adjacent linear toolpaths with a pre-specified curve. Time-optimal trajectory planning and solution existence constraint for arbitrary initial and final velocity/acceleration was proposed. Generate the corner trajectory by minimizing cycle time within geometric error and kinematic limits in one-step. The velocity, acceleration and jerk limits of each axis are fully exploited.