Generation of tool paths for machining free-form pockets with islands using distance maps

In this paper we present a new procedure for generating tool paths using discrete distance maps, especially for dealing with free-form shaped pockets with multiple islands. In this procedure, a discrete distance map is computed by shading a right circular cone having the height of a given offset distance, while moving its apex along the boundary curve segments. Using the discrete distance maps, the proposed algorithm effectively extracts the characteristic points or the valid self-intersection paints of offset curve segments. For an offset distance, one or more offset profiles are constructed without the topological problems by offsetting the boundary curve segments within the parameter values specified by these characteristic points, and connecting them into closed profiles using the topological information contained in the distance map. The gauging-free tool path is constructed by connecting these offset profiles, starting fi-om the innermost offset profile. In the proposed method, we do not need any artificial bridges for a packet with multiple islands to merge the pocket profile and the island profiles into a single boundary profile.