Geometric error modeling and compensation of horizontal CNC turning center for TI worm turning

This article proposes a method to compensate geometric errors of a horizontal CNC turning center for Toroidal Involute worm (TI worm) turning. TI worm is of great advantages for heavy duty transmission due to multi-tooth line contact. Contact situation and performance is influenced by the manufacturing accuracy of TI worm. However, few researches focused on the high-efficiency and high-precision turning method of TI worm. Therefore, tooth profile error prediction and compensation models for TI worm turning were built by the forward and actual inverse kinematics based on the multi-body theory. Firstly, the meshing system of TI worm was established according to the theory of gear meshing. The TI worm tooth surface was reconstructed via Non-Uniform Rational B-Splines (NURBS) fitting. Discrete points of toroidal spiral were calculated for NC turning code generation and correction. Secondly, spatial errors of the discrete points were predicted according to the forward kinematics model. The turning trajectories were modified in opposite direction of the spatial errors. Then, the compensated NC turning codes were obtained based on the instruction of variable pitch thread turning. Simulation and experiment verification of the accurate TI worm turning method and the geometric error compensation strategy were conducted on a three-axis horizontal CNC turning center. The tooth profile errors before and after compensation were compared to validate the effectiveness of the proposed method