Nonlinear dynamic analysis of ceramic motorized spindle considering bearing preload and span

Ceramic motorized spindle is more suitable for high-precision and high-speed machining because of its material with high stiffness, low deformation, and other excellent characteristics. The ceramic bearing assembly and support location are critical elements influencing the stiffness and dynamic characteristics of ceramic motorized spindle. In order to investigate the influence of bearing assembly on the dynamic characteristics of spindle, the relationship between preload and bearing stiffness is determined and a dynamic model of ceramic motorized spindle bearing rotor system is established taking the comprehensive impact of bearing span and preload into account. The bearing stiffness fluctuation caused by bearing preload and bearing thermal deformation is calculated, and the effect of bearing preload and span on the dynamic characteristics is investigated. The results show that the rotor amplitude firstly decreases with the bearing preload and span vary, and then increases. The best assembly combination of ceramic spindle is a preload of 400 N and a span of 190 mm in the speed of 12,000-18,000 r/min. The vibration experiments are conducted on the ceramic motorized spindle, and the average error between experimental date and calculated date is 2.49%, which verifies the accuracy of the model. This study lays a theoretical foundation for further investigation of the dynamic characteristics of ceramic motorized spindle and its structural optimization.