Research On Dynamic Characteristics Of Spindle System And Stability Prediction Of Milling Chatter Under Rotating State

At present,high-speed milling is widely used in the automotive industry,mold industry,aerospace and other industries.While the electric spindle is the main component of the high-speed milling machine,and in high-speed rotating conditions of the electric spindle,the spindle bearing subjecting to centrifugal force,gyroscopic moment and other factors have a significant impact on the dynamic characteristics of the spindle system.In order to predict the chatter stability of high-speed milling more accurately,the following major work is carried out in this paper:(1)The background and significance of the prediction of chatter stability of milling are introduced.High-speed angular contact bearings change with the spindle speed and the research development status of dynamic characteristics of the high-speed electric spindle and prediction method of chatter stability of milling are summarized.(2)Force analysis and quasi-static and pseudo-dynamic analysis of high-speed angular contact ball bearings rolling are completed.Under the high-speed rotating condition,the rolling state of the spindle bearing is analyzed,and each dynamic parameter of the bearing and the change of the radial stiffness of the bearing with the rotating speed under the condition of certain preload are calculated.(3)Considering the influence of bearing stiffness on the spindle system,a spindle-clamp-tool system model is established.The finite element method is used to analyze the change rule of the first several natural frequencies of spindle system with the rotating speed.At the same time,the influence of different tool overhang and different bearing radial stiffness on the first several natural frequencies of the spindle system is also studied.(4)The generation mechanism of chatter in the milling process and the dynamics of milling are modeled.The prediction method of chatter stability of milling is introduced.And the method of zero order approximation of the chatter stability prediction is modeled.Finally,the influence of different milling modal parameters on the prediction of milling chatter stability is studied.(5)Considering the influence of the dynamic characteristics of the spindle system on the stability of milling chatter under high-speed conditions,and the inverse stability approach for stability prediction of milling chatter is modeled and numerically analyzed.It can be concluded that the change of modal parameters in milling at high speed can lead to the change of milling chatter stability lobes diagrams.So the chatter stability is more accurately predicted.(6)The modal test and chatter stability prediction of MMT-50X milling machine under static condition are carried out.At the same time,the milling chatter test is carried out on the material AL7075.The new modal parameters and the new chatter stability lobes diagram are obtained by using the inverse stability approach according to the limit cutting depth and chatter frequency.According to the test results,it is found that there is a deviation between the lobes diagram in the high-speed milling condition and the lobes diagram of the chatter stability in the stationary condition.