A Thermomechanical Modeling and Experimental Validation of the Gear Finish Hobbing Process

Abstract

The current research work aims at developing an analytical modelling of the gear finish hobbing process when the uncut chip thickness may be very small. Numerical models and particularly finite element simulations of this complex material removal process are often limited to one tooth because of the high required computational time. To analyze the performance characteristics of this process, a predictive approach for finish gear hobbing based on an analytical model of orthogonal cutting operation is proposed. To reduce the computational time, a new calculation strategy has been developed. This allows to examine the local parameters which change significantly for each tooth. During the finishing hobbing process of large gears (6 m < diameter < 16 m), the industrial conditions require low cutting speeds (less than 1 m/s) with lubrication. Therefore, in order to consider the effect of lubrication, cutting speed and uncut thickness on the friction coefficient, an appropriate friction law was identified from orthogonal cutting tests. The cutting model has been experimentally validated for different cutting conditions. Finally, the effects of hobbing process on the cutting forces and the tool-chip contact parameters (contact length, pressure, frictional stress and temperature) have been investigated and deeply analyzed using the developed model. The distributions of these local parameters, at each tooth rake face, may be used as a process signature for the resulting condition of the machined surface and subsurface layers.