A constant feed and reduced angular acceleration interpolation algorithm for multi-axis machining

Multi-axis tool paths are currently generated as a set of discrete data poi nts consisting of a position vector, representing the tool tip, and an orie ntation unit vector, representing the tool axis. The CNC interpolator must convert these points into continuous machine tool axis motions. To achieve the highest quality parts, a constant feed and reduced angular acceleration must be maintained throughout the motion. This paper presents a new algori thm for off-line interpolation of the data points, followed by real-time ax is command generation. The splines produced by the algorithm are C-2 contin uous, and independent of machine tool kinematics. Hence the motions produce d will be the same on any five-axis machine tool, hexapod, or robotic arm. Three splines are computed: position, orientation, and reparameterization. The position spline is a near are-length parameterized quintic polynomial s pline. The paper introduces a near are-length parameterized quintic spheric al Bezier spline as the orientation spline. Coordinated motion is accomplis hed with an orientation reparameterization spline. The proposed algorithm i s demonstrated using a practical example. (C) 2000 Elsevier Science Ltd. Al l rights reserved.