Postprocessor for five-axis machining of STL surfaces based on Nagata interpolation and optimization of rotation angles

This paper proposes a postprocessor which applies the appropriate rotation rules to reduce the kinematic error (KE). Our first contribution is an algorithm which minimizes the KE using the Hausdorff distance. The shortest path algorithm includes the constraints relevant to the limits of the linear and the rotation axis. The proposed procedure is compared with state-of-the-art methods. It demonstrates an advantage in terms of the kinematic error for test surfaces characterized by a sharp curvature. The second contribution is testing interpolation methods of the STL surfaces. The first step of this procedure is the evaluation of the tessellation error (TE), i.e., the difference between the actual surface and the local or global interpolation obtained from the STL file. The numerical results show that a simple local interpolation using normal vectors proposed by Nagata performs well. The method has been tested against several state-of-the-art interpolation procedures, demonstrating a significant advantage. The proposed elements are integrated into a postprocessor. The experiments have been performed on a virtual and the actual tilt-table five-axis machining center (Haas VF-2TR).