Research On Design Method Of High-speed Motorized Spindle Based On Dynamic Characteristics Prediction Under Loading Condition

The motorized spindle is the critical unit of high-speed machine tools which directly influence the machining efficiency,quality and precision.But the current design method is mainly focused on the spindle of unload characteristics.Due to the dynamic characteristics of spindle speed under loading condition have important influence on the machining efficiency and machining accuracy for high-speed machining tools,but the study on design method of dynamic characteristics for the this conditions of the spindle are short of systematic and in-depth.Therefore,it is required to make a study of the dynamic characteristics of the motorized spindle under loading condition.The ideas of structure optimization parameter for motorized spindle based on the prediction of dynamic characteristics under loading condition is proposed.Based on modal theory and finite element method,high speed condition of high-speed motorized spindle system is established by the unbalanced force and the dynamic model under external load,the dynamic model of high speed spindle system by unbalanced force and external load excitation at high speed is established,the calculating method of natural frequency,vibration shape and dynamic response is studied.By comparison with the literature,the validity of the established model and analysis method is proved.12kW/30000r/min typical motorized spindle structure are designed,and have the advantage of compact structure,small rotor inertia,fast dynamic response,adapt to the needs of the ultra-high speed grinding.By using the established model and method,the research reveals that spindle system dynamic response varies with the external exciting force,speed,unbalanced quality etc.The dynamic change rules of typical electric spindle system under loading condition with the external exciting force,speed,unbalanced quality was studied.The influence of the size and type of the exciting force,the size and distribution of unbalanced quality and the different speed conditions for the dynamic response of the spindle system rule are studiedThe influence of the spindle static stiffness,critical speed and dynamic deflection by structural parameters such as the span of spindle and the outer diameter of motor rotor is quantitative researched.On the basis of the above research,specific strategies of spindle structure parameter optimization is proposed.properly reduce the spindle span,can improve the critical speed and static stiffness of the spindle system,reduce the sensitivity of the spindle system unbalance quality,reducing the spindle dynamic deformation,thereby increasing the dynamic stiffness of the spindle,improve the performance of the machine tool to resist forced vibration.Under the premise of ensure the output power,appropriate reduce the outer diameter of rotor and reduces the added mass of spindle system,can improve the critical speed.Based on the above research,a spindle test bench is built.the analysis of vibration signal acquisition system by using the experimental platform,the working parameters on the static and dynamic stiffness of the spindle and the dynamic response characteristics are analyzed.The experimental results confirm the rational of research results and theory design on the carrying stiffness characteristics and critical structures of the spindle system.The research work has important engineering reference value to high-speed hydrostatic electric spindle design and hydrostatic bearing structure and working parameters optimization.