Interval partition-based feedrate scheduling with axial drive constraints for five-axis spline toolpaths

Abstract

The feedrate scheduling has received much attention recently because it is one of the most important tasks in the CNC (computer numerical control) spline interpolator which performs better than conventional linear interpolator in both machining smoothness and efficiency. It is acknowledged that the feedrate scheduling of five-axis machine tools under axial drive constraints is extremely challenging due to the complex-coupled motion relationship between five axes and tool tip/orientation. Existing methods mainly schedule five-axis feedrate with the time-optimal purpose, i.e., planning the feedrate as high as possible provided the drive constraints are not exceeded. However, this kind of methods will result in a frequent time-varying feedrate profile, and this doubtlessly goes against with the feed-motion stability. To deal with this problem, this paper proposes an interval partition-based five-axis feedrate scheduling method with the purpose of balancing feed-motion efficiency and stability, under the constraints of axial drive parameters in terms of velocity, acceleration, and jerk. To accomplish this purpose, the integral toolpath is partitioned into non-sensitive (NS), semi-sensitive (SS), and full-sensitive (FS) intervals, according to the relation between required and limited axial feed parameters. The constant speed is scheduled in each FS interval, and the smooth variable speed is scheduled in NS and SS intervals; thus, the feed-motion stability can be ensured without too much reduction of the feed-motion efficiency. Example tests are conducted to illustrate the application of the proposed approach, and it is shown from the illustration results that the proposed method can surely balance the feed-motion efficiency and stability of the five-axis spline toolpaths, under the axial drive constraints.