Thermal energy balance control model of motorized spindle system enabling high-speed dry hobbing process

High-speed dry hobbing has been confirmed as a dominant advanced technique for gear machining due to its outstanding performance in terms of high productivity and environmental friendliness. The motorized spindle system is the key component of the high-speed dry hobbing machine, and its thermal stabilization is of significant importance for the machining precision. However, due to the integration of motor and spindle, the adoption of high cutting speed and the heavy cutting load, thermal energy will accumulate in the motorized spindle system and result in thermal deformation and stability degeneration, which eventually affects the consistency of hobbing accuracy. In this paper, an analytical model is proposed to control the thermal energy balance of a high-speed dry hobbing spindle system by optimizing the thermal energy accumulation with the hob rotation speed, hob axial feed rate, cooling water flow rate and the compressed air temperature. The optimal solution is obtained by solving the proposed optimization model with the simulated annealing method. A motorized spindle system is introduced as a case study and the experimental results indicate that the maximum value of the average temperature of the motorized spindle system is reduced from 39.6 °C to 35.0 °C, an 11.6% margin, and the material removal time is reduced from 2.07 min to 1.06 min, a 48.8% margin, under the optimal condition. Moreover, the average runout value of a hobbed workpiece is effectively controlled, by a 15.7% margin. Therefore, the presented optimization model can give a reference for the selection of suitable process parameters for thermal stability control and higher machining productivity and accuracy.