Research on vibration of ceramic motorized spindle influenced by interference and thermal displacement

The vibration of ceramic motorized spindle determines the machining quality of CNC machine tools. The dynamic characteristics of a motorized spindle were explored under the influence of interference fit and thermal displacement. Using heat transfer theory and bearing Harris theory, the temperature field model of motorized spindle was established, which aims to find the relationship of thermal displacement and interference. In addition, the dynamic and thermal factors were coupled to the dynamic model of the ceramic motorized spindle rotor system, of which the variation rules of bearing stiffness and rotor vibration characteristics were calculated and analyzed. The accuracy of the motorized spindle rotor system dynamic model was verified by experiments. The results show that the interference fit of shaft and bearing decreases with the rotating speed increase under the combined influence of centrifugal force, load and thermal displacement. The vibration was calculated by the dynamic model of motorized spindle rotor system considering dynamic and thermal factors. The maximum error was 3.9 %, which is well consistent with the experimental results. The dynamic characteristics of ceramic motorized spindle can be improved by appropriately increasing the degree of interference tightness at high speed.