Analysis Of Vibration Characteristics Of Hydraulically Supported Spindles Of Ultra-precision Machine Tools And Research On Basic Vibration Isolation

In this paper,an ultra-precision machine is taken as the research background,the bearing molecular dynamics model is established by using Material Studio and LAMMPS software,and the influencing factors of the stiffness of the bearing are analyzed.The finite element model of the machine tool is established by ABAQUS,and the double-layer vibration isolation system is designed.The displacement response analysis of the spindle before and after vibration isolation is carried out.The main research contents are as follows:1)Based on the principle of molecular dynamics,the axial model and radial model of the spindle were established by using Material Studio and LAMMPS software,and the influence of different oil film thickness,different spindle speed and different oil pressure on the stiffness of the bearing was analyzed.The results show that the bearing stiffness increases first and then decreases with the change of film thickness;the bearing stiffness is positively correlated with the spindle speed and the oil pressure under the working condition of the spindle;2)The experimental modal analysis of the ultra precision machine tool was carried out,and the natural frequency,damping ratio and vibration mode of the first 16 steps of the machine tool were obtained.It is found that the natural frequency of the first 8 orders coincides with the frequency range of environmental micro-vibration;The finite element model of machine tool was established by ABAQUS,and modal analysis was carried out.The first 8 natural frequencies coincide with the measured frequency,the maximum error is less than 6.47%,and the vibration characteristics are consistent with the measured vibration characteristics,which proves the validity of the model;3)The white noise random signal was generated by Matlab to simulate the micro-vibration of the environment.The vibration signal was loaded into the machine tool from three directions of X,Y and Z at the same time,and the displacement response of the spindle under 16 kinds of combined conditions was obtained.The results show that the displacement responses of the three major axes under environmental micro-vibration all exceed the requirements of the machining precision and the vibration isolation design must be carried out;4)The double-layer vibration isolation system is designed for the ultra-precision machine tool,and the displacement response analysis of the vibration isolation system under environment micro-vibration is carried out.The analysis results show that after the isolation system,the displacement response of the three directions of the spindle is greatly reduced,which meets the requirements of ultra-precision machining;5)The effects of vibration isolation parameters such as the stiffness of the upper and lower layers,the damping ratio,the mass ratio of the middle mass to the machine are taken into account respectively.The simulation results show that:as the spring stiffness increases,the displacement response of the bearing in three directions increases,and changing the upper or lower spring stiffness has an approximate effect on the vibration isolation of the system;with the change of damping ratio,the displacement response of the bearing is reduced in three directions,and the damping ratio of the upper vibration isolator is more obvious;with the change of mass ratio,the displacement response of the spindle first decreases and then increases,and the vibration isolation effect is better when the mass ratio is close to 1.