Tool-adaptive offset paths on triangular mesh workpiece surfaces

Path-oriented, computer-controlled manufacturing systems work by moving a tool along a path in order to affect a workpiece. A common approach to the construction of a surface-covering path is to take a finite family of offset curves of a given seed curve with increasing offsets. This results in a set of quasi-parallel curves. The offset is chosen so that a tool moving along the curves has the desired impact at every surface point. In cases where the region of influence of a tool is different across the surface, an offset value necessary in one region may lead to a curve offset lower than required in other regions. The paper presents a general method of offset curve construction with tool-adaptive offsets. The offset path is obtained as a family of iso-curves of an anisotropic distance function of a seed curve on the workpiece surface. Anisotropy is defined by a metric tensor field on the surface. An application-independent algorithmic framework of the method for workpiece surfaces represented by a triangular mesh is presented. Its usefulness is demonstrated on the problem of varying cusp heights for milling and for spray coating of surfaces with a spray gun moved by an industrial robot. •We present a method for automatic tool-adaptive path planning for freeform surfaces.•The method is based on an implicit (level set) path representation.•The method is worked out for freeform workpieces represented by triangular meshes.•We demonstrate the usefulness of this approach for milling and spray coating.