Collision avoidance and orientation planning for ball-end cutter

Propeller blades have freeform surfaces, and the overlap among the blades limits the adjustment range of cutter orientation, making it extremely difficult to generate the required cutter orientation. Therefore, to assist in quickly designing a safe and reasonable machining scheme, a projection-offset method is designed to calculate the feasible region of a ballend cutter and an XYZ-3RPS hybrid kinematic mechanism. Based on this, a reasonable and smooth cutter orientation can be generated using path-planning and trajectory-optimization algorithms. To this end, a method for obtaining point clouds was first developed. By arranging the point clouds of a blank in the cutter path order, the changes to the blank during the machining process can be reflected through point-cloud deletion. A hierarchical bounding box is established for the moving platform of the cutter, spindle, and mechanism, which can realize the quick screening and classification of collision-point clouds. Second, the collision points are projected onto the same plane, an envelope boundary of the projected point cloud was constructed using an alpha-shapes algorithm, and its cross boundary trimmed using the auxiliary boundary method to obtain the feasible region at the cutter contact point. Moreover, to reduce the computational load, an interpolation method, which reduces the number of calculations, is used. The basic rules for cutter-orientation generation were established using a planning function. Then, the cutter-orientation path was smoothed using the trajectory-optimization algorithm to prevent the cutter from swinging violently. Finally, the effectiveness of this method was verified through propeller experiments.