Research on hobbing accuracy of flexspline tooth profile of harmonic drive

Abstract

Harmonic drives are critical components in robotic joints, and the hobbing accuracy of flexspline tooth profiles is essential for the transmission accuracy and operational stability of harmonic drives. The objective of this study is to propose an analysis method for the hobbing accuracy of flexspline tooth profiles. Firstly, a synthetic volumetric error model considering both geometric errors and thermal deformations was established based on the multi-body system theory. This model demonstrates the correlation between individual errors of the hobbing machine tool components and the spatial machining accuracy. Furthermore, the kinematic relationship of flexspline hobbing was established. Through kinematic analysis, it is concluded that the radial position deviation of the hob along the Y direction in the hobbing coordinate system directly affects the machining accuracy of the flexspline tooth profile. This deviation leads to variations in the tooth thickness of the flexspline tooth profile. Finally, theoretical tooth thickness deviations of the flexspline tooth profiles were predicted. Actual measurements of the flexspline tooth profiles were conducted, obtaining measured tooth thickness deviations. The measured values were smaller than the theoretical values, indicating the correctness of the established synthetic volumetric error model and the effectiveness of the proposed analysis method for evaluating the hobbing accuracy of flexspline tooth profiles. This research provides valuable technical references for error tracing and compensation in the gear hobbing process.

Keywords

• flexspline tooth profile
• hobbing
• geometric error modeling
• thermal deformation errors
• tooth thickness error