Contour-parallel offset machining without tool-retractions

Contour-parallel offset (CPO) machining uses successive offsets of the boundary curves of the machining region as the tool-path-elements (TPEs). For the efficiency of the CPO machining, it is very important to minimize the number of tool-retractions, which cause additional tool movements and do not contribute to the actual cutting. Presented in the paper is a CPO tool-path linking algorithm, which guarantees 'zero' number of tool-retractions. The algorithm employs the concept of a 'TPE-net' providing the information on the parent/child relationships among the TPEs. By planning a route through the TPE-net, a CPO tool-path without tool-retractions can be generated.