Based On The Dynamic Characteristics Of The High-speed Electric Spindle Under The Force-thermal Coupling

High-speed precision machining is now the mainstream development direction of manufacturing industry.High-speed precision machine tools are the equipment foundation of high-speed precision machining.As the main component of highspeed precision machine tools,high-speed motorized spindle has good dynamic characteristics,which has become an essential condition for modern high-speed motorized spindle.Based on Hertz contact theory,heat transfer and elasto-plastic mechanics,the coupling analysis of pretightening force,heat and stiffness,which determine the dynamic characteristics of the spindle,is carried out in this paper.At the same time,the influences of the structural forms of the spindle,such as installation mode,overhang and bearing span,are also considered,and the following results are obtained:(1)Based on Hertz's contact theory,the static load model and pseudo-dynamic model of the bearing are established,and the change of the bearing after preload is applied in the static state is analyzed,and the change rule of axial tightening amount and contact angle with preload under static load is obtained.During the rotation of the bearing,the contact angle between the inner and outer parts of the bearing,the contact load between the inner and outer raceways of the bearing and the rolling elements,and the variation law of the bearing stiffness with the rotation speed are analyzed.(2)The spindle model of motorized spindle based on timoshenko beam theory is established.The bearing is used as the support of the spindle,and the dynamic characteristics of the spindle are analyzed.The influence law of rotational speed and preload on the dynamic characteristics of motorized spindle is obtained.(3)Based on tribology and heat transfer,the heat generated by the friction of the bearing is calculated,the heat transfer model of the bearing system is established,the thermal impedance of each node of the bearing system and the temperature of each node of the bearing are calculated,the bearing heat and the contact load of the bearing are coupled,the axial displacement and radial displacement of the bearing are deduced according to the temperature change of the bearing,the influence of the rotating speed and the pretightening force on the temperature rise and the thermal displacement of the bearing,the influence of the bearing due to the thermal displacement on the stiffness of the bearing and the influence rule of the pretightening force of the thermal displacement and the rotating speed on the dynamic characteristics of the spindle are analyzed.(4)The influence of different structural parameters such as the installation mode,span and overhang on the dynamic characteristics of the spindle is discussed.The contact loads of spindle bearings are different when the motorized spindle is placed horizontally and vertically.The bearing force,bearing stiffness and bearing temperature rise are calculated when the horizontal motorized spindle and the vertical motorized spindle consider the gravity of the rotating shaft and rotor,and the influence of different installation methods on the dynamic characteristics of the spindle is analyzed.Span and overhang are important structural parameters of the spindle.The influence of different span and overhang on the dynamic characteristics of the spindle is analyzed.