Research On The Dynamic Characteristics Of High-speed Motorized Spindle And The Influence Of Multiple Working Conditions On It

With the rapid development of mechanical manufacturing technology,high-speed motorized spindle has become the core component of today's CNC machine tools,and its performance requirements are becoming higher and higher.Whether the motorized spindle has good dynamic characteristics has become a necessary condition to ensure the machining accuracy.Bearing contact stiffness is affected by preload,and the change of rotational speed at high speed leads to friction heat of bearing,which further affects contact stiffness by contact deformation.Bearing as the supporting component of motorized spindle its stiffness determines the dynamic characteristics of motorized spindle.Based on Hertz contact theory,friction theory,heat transfer theory and rotor dynamics theory,this paper analyzes the dynamic characteristics of motorized spindles under multiple working conditions,and the following results are obtained:Based on Hertz contact theory,the statics model and pseudo-dynamic model of angular contact ball bearing are established,the contact deformation,contact load and contact Angle of bearing under the action of preload are analyzed under the action of static and high speed two different states,and the relationship between bearing contact rigidity and preload is obtained.Based on the tribology and heat transfer theory,the heat generation model of angular contact ball bearing is established,and the variation law of preload,rotational speed,contact Angle and friction moment is analyzed.The heat transfer model of the bearing is established,the temperature of each node of the bearing is calculated by the thermal impedance method,and then the thermal displacement of each part of the bearing is derived.The variation law of temperature rise,rotational speed,thermal displacement and bearing parameters is analyzed.Considering the effect of centrifugal force,the variation law of thermal displacement and stiffness at different rotating speeds is finally analyzed.Based on rotor dynamics theory,the dynamic model of spindle system is established.Based on the above theoretical basis,the dynamic characteristics of motorized spindle under the following working conditions are analyzed:(1)Considering the influence of preload and temperature,the variation rule between preload and the natural frequency of each order of the spindle system is obtained,and the mode of each order of the spindle system is described,so as to obtain the variation rule between the temperature rise and the natural frequency of the spindle under this working condition.(2)Establish the stress model of the spindle system during high-speed cutting,and get the variation rule of the natural frequency of the spindle system with the preload under this working condition.(3)Establish the dynamic model of motorized spindle under different working conditions of bearing housing installation.The differential equations of motion of the spindle system are derived.The tilt Angle and coaxiality of the installation are transformed to calculate the variation rule between coaxiality and the natural frequency of the spindle system.At the same time,the first three natural frequencies of the spindle system are verified through simulation analysis under this working condition.Finally,the influence of this working condition on machining is calculated.