A Feature Free Approach to 5-Axis Tool Path Generation

Abstract

In recent years, CAD/CAM integration for machining has been based on the concept of manufacturing features. In this paper we present an overview of an alternative scheme to integrate CAD with CAM. Instead of decomposing the design into manufacturing features, we generate tool paths directly from the shape of the workpiece using visibility and accessibility arguments. This approach builds on the work of a number of previous efforts to bring concepts from robotic path planning into the realm of NC planning. We present a hardware approach for computing visibility rapidly. This information is then used to determine the “principal directions”, or setups, around which the search will be conducted to remove material from the workpiece. The machining is conducted in two stages. The first stage, global roughing, is performed for each principal direction. The bulk of the material is removed through 5-axis roughing tool paths. Algorithms have been developed to generate these tool paths in an efficient way. The removal volume is first stratified into “4−1/2D machining pockets”, for which tool paths are generated with simple “space filling 2D curves based on the Voronoi Diagram. After global roughing, the surface of the part can be finished with “face based finishing.” In this step, each face is independently machined to the required finish and accuracy using a face-oriented, rather than feature-oriented, approach. The primary concern is to meet accessibility constraints for each face while generating tool paths individually. Once toolpaths have been generated, we simulate them and correct residual intersection problems before outputting final NC code. Since this is an overview paper that attempts to summarize current and future research in an ongoing project, we concentrate on some key issues such as accessibility, while only summarizing other individual ideas briefly. We also present some experimental results through illustrations.