Rolling ball method applied to 3½½-axis machining for tool orientation and positioning and path planning

Abstract

In 3½½-axis machining, the machined part surface is partitioned in pre-processing in order to calculate the tool position and patch boundaries and then machined in patches, thereby minimizing the intermediate manual part re-positioning and the overall machining time. Each patch requires a constant, but different, tool orientation. In previous research, local properties have been used to subdivide surfaces into patches. For an ideal tool position and orientation, however, the tool’s shape and curvature should exactly match the shape and curvature of the part surface. The rolling ball method, originally developed for 5-axis machining, considers the regional characteristics of tool positioning. This work extends the rolling ball method to 3½½-axis machining, thereby successfully delivering 5-axis quality with currently installed 3-axis computer numerical control milling machines. The pseudo-radius of curvature provides a novel geometrical subdivision criterion. Two Bézier curved surfaces are tested and compared with the 5-axis rolling ball method. Two additional surfaces are presented to further demonstrate the partitioning capability of the method. The results suggest that the rolling ball method for 3½½-axis machining is comparatively competitive in performance and quality.