Efficient cutting path planning for a non-spherical tool based on an iso-scallop height distance field

Abstract

Iso-scallop height machining means, when machining a freeform surface, the scallop height between any two neighboring tool paths on the surface will be a constant (i.e., the given threshold), which is preferable among various freeform surface machining strategies due to its high machining efficiency as well as better machine tool’s dynamics. However, all the existing iso-scallop height path planning methods pertain to only the ball-end or flat-end types of tools. In recent years, the non-spherical cutting tool has become more and more popular, especially for five-axis machining of complex freeform surfaces, majorly owing to its non-constant curvature which can be utilized to adaptively fit the tool to the surface to both avoid the local gouging and enlarge the cutting width. However, there have been no reported works on iso-scallop height five-axis tool path generation for a non-spherical tool, and, in this paper, we present one. Specifically, we first define and construct two fields on the surface to be machined-the collision-free tool orientation field (vector) and the iso-scallop height distance field (scalar). The iso-lines of the scalar field and their associated tool orientation field vectors then naturally serve as potential iso-scallop height five-axis tool paths, and we present a propagation-based algorithm to construct the desired tool path from the iso-lines. The computer simulation and physical cutting experiments confirm that everywhere on the surface, except maybe near the saddle curves of the scalar filed, the scallop height is exactly the given threshold. By adding the saddle curves as extra tool paths, the final machined surface then is assured of the required scallop height requirement.