Time-optimal Path Planning of Multi-axis CNC Processes Using Variability of Orientation

Abstract In multi-axis processes, such as welding or 3D printing, the determination of the orientation of the tool relative to the workpiece is usually determined by technology-dependent geometric algorithms. In the simplest case, the orientation of the tool is defined according to the surface normal vectors of the workpiece surfaces. However, with large curvature gradients, this method can lead to jumps in the orientation which lead to unwanted stopping of the translational motion. In the linear interpolation of this movement, the path speed usually decreases significantly due to the relatively large compensating movement of a kinematic system. This type of path movement usually has negative effects on the CNC process, which requires constant path velocities. This paper describes a method for time-optimized path planning that utilizes the orientation tolerances of multi-axis processes. Orientation tolerances are process-dependent tolerances that indicate which orientation ranges (angular positions) from tool to workpiece are permissible without decreasing the process quality. The potential time savings of this method are shown with an extreme example of a planar 3-axis kinematics and on an industrial 7-axis CNC system.