Spiral toolpath generation method for pocket machining

Spiral toolpath plays a significant role in 2.5D pocket machining with the advantages of free of sharp corners and without unwanted un-cutting materials. Technically, efficiency of pocket machining toolpath is determined by its smoothness and total length. Most of existing spiral toolpath generation methods pay more attention on acquiring a smooth toolpath without tool retractions, lacking consideration of total length minimization. In this work, an improved spiral toolpath generation method based on medial axis (MA) transformation is developed to decrease the total length of toolpath, so as to improve the machining performance. The proposed method can be applied to pockets with arbitrary geometries. To avoid unwanted interference between cutting tool and pocket boundary, cutting tool accessibility analysis is firstly conducted. MA sub-cycle for each layer is acquired by trimming the original MA of the pocket. Toolpath of each layer is determined by the envelope curve of a set of disks with various diameters that located on its MA sub-cycle. Toolpath between adjacent layers is guaranteed to be free of intersections. The spiral toolpath is generated by connecting the isolated toolpaths of all layers based on partially linear morphing. Then a toolpath modification algorithm is developed to smooth the spiral toolpath around root node of pocket MA. Finally, machining experiment is conducted to validate the advantages of the proposed method on machining efficiency improvement.