Thermal effect modeling of axial static stiffness of motorized spindle unit

Abstract

In order to investigate the thermal variations of axial static stiffness of motorized spindle unit, a thermal modeling method of spindle axial static stiffness is established by combining the numerical simulation technology with analytical method. Firstly, based on a thermoelastic ring cylinder model and the Hertz contact theory, the analytical model of temperature rise -axial static stiffness thermal variation effect of spindle-angular contact ball bearing system is constructed; then, the spindle structural thermal model considering its coolant heat transfer is obtained by using the finite element heat-fluid-solid coupling simulation technology, to solve temperature rises of spindle bearings. Based on them, the Bushing element is used to analyze the stiffness of the bearing assembly in the thermal-structural coupling simulation modeling of motorized spindle unit, and thus to simulate the thermal variation effects of spindle axial static stiffness. Ultimately, the variation tendencies of the spindle axial static stiffness under various thermal conditions are analyzed by using this model, and the obtained results are compared with their corresponding test data. The comparisons show that: this modeling method can accurately predict the thermal variation tendencies of axial static stiffness during spindle operations. Then the temperature rise of spindle structure can cause its axial static stiffness to harden, which is associated with the thermal increase of bearing preload. The conclusions have the guiding significance for thermal balance design and optimization of spindle structure.