Design And Dynamic Characteristics Analysis Of Radial And Spherical Aerostatic Bearing Shafting

With the precision and ultra precision machining technology becoming a measurement of a national machinery industry,the ultra precision machine tool spindle axis of the research has been paid more and more attention.The gas lubricated bearing has the advantages of high machining accuracy,no friction and good controllability.So it has been used more and more in the spindle system of ultra precision machine tools.With the continuous development of gas lubrication technology,ultra precision machine tool spindle system with gas lubricated bearings will become a new trend in the future.Due to the fact that the main shaft system supported by the common radial gas bearing is difficult to install and can not automatically adjust to the heart,this paper designs a new main shaft system.The purpose of this paper is to simplify the installation process and improve the rotation accuracy of the spindle through the automatic self-aligning function of the hemisphere bearing.In this paper,the static and dynamic characteristics of bearing and spindle are analyzed.The Reynolds equation is simplified by finite difference method.The static performance of radial gas bearing is calculated by Matlab software.Gambit is used to model the hemisphere bearing.Fluent is used to simulated the bearing characteristics of the spherical gas bearing.By adding small perturbations and using the linear perturbation method model Reynolds equation is established in steady Reynolds equation.According to the equation,the dynamic characteristic parameters of radial and hemispherical gas bearings are obtained.Based on the theory of rigid body dynamics,the dynamic model of the spindle rotor is established.According to the dynamic characteristics of the bearing,the formula of the principal axis unbalance response is derived.The free vibration of the main shaft is analyzed by means of modal analysis,the vibration frequency of the spindle is obtained and the critical speed of the spindle is calculated.In this paper,theoretical analysis and simulation results show that the design of the main shaft meet the needs of the existing ultra precision machine tools.