A thermodynamics coupled modeling approach for analysis and improvement of high-speed motorized spindle system

The performance of high-speed motorized spindle system is greatly affected by spindle's thermal and dynamic behavior. So it is very important to predict these properties in design stage of spindle system. However, the thermal and dynamic behaviour reacts upon each other for the high rotational speed and complex structure of the spindle system. To control and optimize the dynamic behaviour and the temperature rise of spindle, this paper developed a dynamic and thermal coupled model of the spindle system by using the finite element method (FEM). The shaft and rotor were modeled as Timoshenko's beam, the rational interference fit between shaft and rotor was treated as mass-spring combinations, the bearings were modeled as nonlinear spring element. The thermal analysis procedure contained the calculation of heat generation and confirmation of boundary condition. The accuracy of this coupled model was validated by corresponding experiments. With this coupled model, the thermal and dynamic performance of the spindle system was studied. The effects of rotational speed, axial preload and material of bearing and the diameter of shaft on thermal and dynamic behavior were analyzed. The spindle system was optimized with the result of analyses above. After optimization, the temperature rise of spindle system falls significantly to 24.5 degrees C, which was 30.2 degrees C before, while the dynamic stiffness at working speed increases from 156 to 197 N/mu m.