Algorithm of variable forward step size planning in freeform surface machining

Multi-axis machine is widely used in freeform surface machining. The curve of tool path is discretized to line segments to get the cutter contact (CC) points according to chordal deviation error (CDE) on conventional method and mid-point point method is applied in the verification of maximum CDE. Shortcoming of the mid-point method is that it may lead to wrong forward step size when sign of the curvature of the two adjacent discretized points is opposite. A new algorithm for curve of tool path discretization is presented to improve the precision of the forward step size, so the forward step size is as large as possible and the CDE is uniform in every line segments. The results showed that the maximum CDE is not locate on the middle point of the two adjacent parameter points, this showed that the conventional simplified mid-point method is not as accurate as the new method.