Spiral tool paths for high-speed machining of 2D pockets with or without islands

Abstract

Abstract We describe new methods for the construction of spiral tool paths for high-speed machining. In the simplest case, our method takes a polygon as input and a number δ>0 and returns a spiral starting at a central point in the polygon, going around towards the boundary while morphing to the shape of the polygon. The spiral consists of linear segments and circular arcs, it is G1 continuous, it has no self-intersections, and the distance from each point on the spiral to each of the neighboring revolutions is at most δ. Our method has the advantage over previously described methods that it is easily adjustable to the case where there is an island in the polygon to be avoided by the spiral. In that case, the spiral starts at the island and morphs the island to the outer boundary of the polygon. It is shown how to apply that method to make significantly shorter spirals in some polygons with no islands than what is obtained by conventional spiral tool paths. Finally, we show how to make a spiral in a polygon with multiple islands by connecting the islands into one island. Highlights It is described how to construct a spiral to be used for pocket machining. The spiral respects a user-defined maximum stepover distance between neighbouring revolutions. The algorithm can create a spiral that morphs an island to the boundary of the pocket. The obtained spirals are in some cases much shorter than previously described spiral toolpaths. The algorithm is fast and a popular industrial strength implementation has been created.