A Practical Approach to Generating Accurate Iso-Cusped Tool Paths for Three-Axis CNC Milling of Sculptured Surface Parts

Abstract

In three-axis computer numerically controlled (CNC) machining of sculptured surface parts, the tool path pattern is crucial to surface quality and machining time. A well-known tool path pattern—iso-cusped tool paths—over sculptured surfaces can save manufacturing time by eliminating redundant machining and reducing manual grinding, while other tool path patterns cannot; thus, this pattern has been accepted in industry. However, accurate iso-cusped tool paths are difficult to plan for three-axis CNC machining of sculptured surfaces when using bull-nose or flat end mills, and the solutions currently available are impractical and/or inaccurate; consequently, these tool paths are rarely used in industry. To solve this problem, this work proposes a new, practical approach to generating accurate iso-cusped tool paths in the process planning for sculptured surface parts. The main features of this work include: (1) defining a planar virtual cutting edge with a closed-form formula in order to accurately represent the geometries of cusps, and (2) calculating cutter contact points of iso-cusped tool paths based on the relationship between these paths and the cutting edges. This approach can be easily implemented into computer-aided manufacturing (CAM) software systems to promote the usage of isocusped tool paths in the manufacturing industry.