Abstract: When the five-axis CNC system executes the 3D cutter radius compensation function, the angle between two adjacent radius compensation vectors would be very large if the tool axis vector nearly coincides with the normal vector. This phenomenon will cause the linear axis moving drastically. The reason for this phenomenon is analyzed based on building the transmission relation from the cutter contact point to the cutter location point, and then to the machine axis. The algorithm is advanced，by taking the flat-bottomed tool as an example,to control the severe motion. By optimizing the direction of the radius compensation vectors in the singular area, the phenomenon that two adjacent radius compensation vectors point to opposite direction is eliminated. Further, the speed of the linear axis could reduce into the allowed range by interpolating new points. Compared with the assignment method with the adjacent radius compensation vector, such algorithm has higher generality and better effect. A simulation experiment is performed to verify the correctness and the effectiveness of this algorithm.

Key words: 3D cutter radius compensation, Five-axis machining, Motion control, Singular point