Toolpath topology design based on vector field of tool feeding direction in sub-regional processing for complex curved surface

Conventional global processing technology with uniform processing parameters for complex curved surface parts easily tends to uneven error distribution and local out-of-tolerance, and the sub-regional processing method is proposed. However, existing criterions for surface segmentation are merely based on the geometric feature, lacking comprehensive consideration of feeding direction and feeding motion stability during processing, which induces local out-of-tolerance and obvious cutting vibration. A toolpath topology design method in sub-regional processing based on the vector field of tool feeding direction is proposed. By calculating optimal feeding direction at each cutting contact point through a bi-objective optimization model, the space vector field is built by the optimal feeding direction. Then, the primary surface segmentation is achieved based on the divergence and the rotation of the projected vector field, and after fitting of the streamline by feeding vectors, the surface subdivision is finished by judging the abrupt change of kinematics parameters when the axes of machine tool feed along streamlines. Finally, two frequently-used toolpath modes are designed in sub-regions based on the shape feature of sub-regional streamline and the sub-regional toolpath topology is generated. The comparison experiments show that surface roughness and profile error of the machining region decrease by 22.52 % and 40.21 % compared with conventional global processing, which proves that the proposed method can reduce machining error and improve processing quality effectively. The research provides important guidance for toolpath generation of the complex curved surface parts in engineering practice.