A simple method for invalid loops removal of planar offset curves

The function of curve offset is of importance in the process of generating a machining tool-path. The robustness of curve offset is compact with reliable invalid loops removal algorithms. The traditional method based on interference detections in searching for all contact positions is a time consuming process and prone to misunderstanding. In order to improve such removal function, a new algorithm called the forward locus tracing method (FLTM) was introduced here. The FLTM searches for all intervals split by intersections of complicated planar curves directly and transforms 2D transversal intersection problems into 1D interval identifications. This proposed mapping process in FLTM may simplify the structure of tasks and be implemented by a computer program easily for CAD systems. Some examples with multiple loops were demonstrated and the results present considerable efficiency and reliability in the offset operation.