Jixie chuandong (Jun 2023)
Hobbing Error Analysis of Harmonic Gear Large Modified Flexspline and Hob Design
Abstract
The forming mechanism of large modified flexspline is studied based on hobbing simulation calculation, the theoretical machining error of tooth surface and its causes are analyzed, and the hob is redesigned to improve the hobbing accuracy of large modified flexspline. The parameter equation of a series of hob cutting edges is established, the mutual position and spatial motion relationship of the hob and the workpiece are determined according to the geometric parameters of hob and workpiece and machining parameters, and the gear hobbing simulation is carried out. According to the forming characteristics of hob multi-edge cutting, the theoretical machining error evaluation model of tooth surface is established to simulate the hobbing error. The hob is redesigned based on the principle that the normal base pitch of hob is equal to that of gears during hobbing to reduce the hobbing tooth surface error. It is found that the tooth profile error near the tooth top will be large when the standard hob is used to machine the large modified flexspline, because the number of cutting edges of standard hob is insufficient and the tooth top will be under-cut; the new hob which module and pressure angle are different from that of the standard hob can realize the complete cutting of each tooth of large modified flexspline with only a few cutting edges, and the machining error of the tooth surface is smaller than that of the standard hob when the tooth surface is completely cut. The research results can provide important reference for the study of hobbing accuracy control of large modified flexspline and the selection of hob parameters.
