Toolpath generation in sub-regional processing with constraint of constant scallop-height at boundary for complex curved surface

Complex curved surface parts are widely applied in the manufacturing industry for specific functions. With the continuous improvement of the geometric complexity and the machining requirement, the conventional processing technology with uniform processing parameters is no longer applicable for this kind of parts, and the sub-regional processing with variable parameters is proposed. However, the obvious machined trace at the boundary between sub-regions appears easily in this way, which restricts the processing quality of complex curved surface parts seriously. To reduce the machined trace and realize the precise toolpath stitching, a toolpath generation method in sub-regional processing with constraint of constant scallop-height at boundary for complex curved surface is proposed. Firstly, the formation mechanism of the machined trace at the boundary between sub-regions is analyzed. Taking into account the geometric feature of the curved surface, the calculation model for the distance between boundary and cutter contact (CC) point is built. With constraint of constant scallop-height, the critical curve of CC points for the boundary between sub-regions is constructed. Then, the geodesics for the critical curve of CC points are calculated in side-step direction with a numerical method. The theoretical CC points on the geodesics are generated according to the estimated scallop-height and modified by the sensitivity analysis. Finally, the toolpaths are generated by connecting the theoretical CC points orderly and the actual CC points are determined in feed direction. A comparison experiment is carried out to verify the feasibility of the proposed toolpath generation method. The experimental results show that with the proposed method, the maximum of the profile deviation and the profile arithmetic average error at the boundary between sub-regions are 9.0 mu m and 2.3885 mu m respectively, which decrease by 74.43% and 34.98% compared with the results for the iso-level method. This research proves that the proposed toolpath generation method can realize the precise toolpath stitching and improve the processing quality in sub-regional processing, which provides guidance for the precision machining of the complex curved surface parts.