Offset error analysis of ball-end mill for cutter-path generation from point-based surfaces

Moulds and dies with sculptured surfaces are usually finished using a three-axis computer numerically controlled milling machine with a ball-end mill. In this paper, the surface shapes are defined by a rectangular grid of surface points and the inverse offset method (IOM) is used to generate the cutter paths. The error of the offset (cutter path) points generated by the IOM due to spacing of surface points is determined. The error analysis enables an appropriately dense set of points to be chosen so that the offset surface can be generated within a specified tolerance.