Pattern detection for toolpath generation on triangular meshes for 5-axis CNC machining

Abstract

Toolpath generation for freeform triangular meshes for 5-axis milling machines using an optimal feeding direction (OFD) field is an important topic in subtractive manufacturing technology. By considering parameters in both the CAD and the CAM stages, there exists a direction(s) at every cutter contact (CC) point, such that the machining efficiency is maximal. The directions could form a special structure which can be detected for toolpath generation on the CAD stage. In this paper, a novel toolpath generation method is proposed to create a toolpath for freeform triangular meshes by detecting regular structures of the OFD in the parametric domain using moment invariants. Three common templates, corresponding to standard toolpath structures, are considered: (1) curl (contour/spiral contour path), (2) star/spiral (radial path), and (3) shear (zigzag path). Mesh parameterization is used to flatten the 3D triangulated surface. A transfinite interpolation (TFI) is utilized to construct the toolpath on the flattened surface. The final toolpath is then obtained by the inverse map. The proposed method has been compared with conventional and standard commercial toolpaths. Numerical results show that the pattern detection algorithm helps to find an appropriate toolpath strategy. The generated toolpaths follow the OFDs closer than the competing methods, and therefore, require shorter machining time.