An improved tool path discretization method for five-axis sculptured surface machining

In five-axis machining of sculptured surfaces, the cutting tool is unable to continuously trace the intended curved tool path due to limitations of existing controllers for the commercial machine tools. Current industrial practice is thus to discretize the continuous tool path into a finite number of cutter contact (CC) points. An improved method of tool path discretization for five-axis sculptured surface machining is presented in this paper. While the tool posture along a tool path is tuned to ensure maximized material removal rate and to avoid gouging to the machined surface, the forward step lengths, characterized by the consecutive discretized CC points, are determined by maintaining the machined surface error within the specified tolerance. The conventional method employs chordal deviations to estimate the machined surface errors of the interpolated tool movements between consecutive CC points, which have been referred to as the geometry-based errors. It has been found that chordal deviations are not reliable estimations of the geometry-based errors. As such, the geometry-based errors are accurately evaluated in this work and the related algorithms are implemented to the machining of a typical Bezier surface patch. The results showed a reduction of about 30% in the number of discretized tool path segments compared with those of the conventional method.