A method for thermal characteristics modelling of hob assembly on dry hobbing machine

Gear hobbing is the use of machinery to manufacture external gears. With the booming motor industry, there are more requirements for gear hobbing accuracy than ever before. Thermal error - as a major source of error in a dry hobbing machine - must be effectively compensated to achieve accuracy. Thus, studies on the thermal error of hob assembly are important both in theory and practice. This paper discusses the development of a valid numerical modelling method for the hob assembly of a dry hobbing machine. The equations used to determine the values of heat sources and heat transfer coefficients are given. The temperature field and thermal deformation of the hob assembly were obtained by thermal-structural coupling numerical simulations. Numerical results showed that the deformation can maximally reach to 94.5 mu m, which is non-ignorable in the thermal deformation analysis of the whole dry gear hobbing machine. Subsequently, by comparing the simulation results and experimental data, the newly proposed method to determine the forced convection heat transfer coefficient proved more fitting for describing the airflow pattern inside the gear hobbing zone. The satisfactory agreement between simulation results and experimental data also suggests that the numerical analysis method proposed in this paper can provide an effective research tool to optimize the design of hob assembly. And the results obtained by the proposed method can be used for thermal error modelling in real error compensation.