Abstract: Currently existing tool posture control methods can’t ensure the smooth motion of tool orientation, which may result in discontinuity of velocity and acceleration of rotation axes and may bring about problems of low accuracy and rough surface. In order to solve these problems, a tool orientation smooth interpolation algorithm that can make velocity and acceleration of rotation axes continuous is proposed. In this algorithm, local rotating coordinate systems are established according to the start and the end tool orientation vectors of each segment. The orientation spline of each segment can be indicated as a function of tilt angle and projection angle. The property of C2 continuity of the orientation spline can then be used for solving the tilt angle and projection angle. The feasibility and the effectiveness of the algorithm are tested by simulated examples. The results show that the algorithm can ensure the continuity of velocity and acceleration of rotation axes.

Key words: Five-axis CNC machining, Orientation spline, Tool orientation smooth interpolation, Tool posture control