Research On Accurate Simulation And Law Of Rotation Accuracy Of Hydrostatic Spindle With Controllable Restrictor

The spindle rotation accuracy directly affects machining accuracy and is an critical index for evaluating machine tools performance.The controllable restrictor hydrostatic bearing is used as supporting part.Due to its large load capacity,high rigidity and adjustable controllable throttle characteristics,it can greatly improve the rotation accuracy of the spindle.Some scholars have conducted in-depth research on it.However,due to the viscosity of the oil,the friction and shearing effect in actual work will increase the temperature of the oil film,which will result in thermal deformation of shaft and bush.The amount of deformation is at the same level as the thickness of the oil film,which will seriously affect the rotation accuracy of the spindle.However,the research on rotation accuracyt of controllable restrictor hydrostatic spindle has ignored the bearing temperature problem.To accurately predict the rotation precision of the spindle,this problem needs to be solved urgently.The main work of the article is as follows:(1)According to the fluid lubrication theory,heat transfer theory and thermoelastic deformation theory,this article solves the bearing fluid domain and solid domain simultaneously.In addition,this article establishs the Fluid-Solid-Heat coupling mathematical model of controllable restrictor hydrostatic bearing that can calculate the bearing temperature field and thermal deformation,and the Fluid-SolidHeat coupling simulation algorithm for bearings that can reflect the interaction between bearing pressure field,temperature field and thermal deformationthe is proposed.Realizing the accurate calculation of bearing temperature field and thermal deformation.(2)Based on the established the Fluid-Solid-Heat coupling mathematical model of controllable restrictor hydrostatic bearing and the corresponding algorithm,this article quantitatively simulates the temperature field and thermal deformation of the bearing under different speeds and eccentric conditions,reveals the influence of spindle speed and eccentricity on bearing temperature field and thermal deformation.The research shows that spindle speed has a great influence on bear temperature and thermal deformation.When the spindle speed is 4000 r/min,the radial thermal deformation of the bearing is about 27% of the thickness of the oil film.(3)Considering the temperature of the bearing,the spindle rotation accuracy is characterized by calculating the fluctuation radius of the spindle.An accurate simulation model of the controllable restrictor hydrostatic spindle rotation accuracy is established,and an accurate simulation algorithm of the spindle rotation accuracy that takes into account the bearing temperature is proposed to achieve an accurate simulation of the spindle rotation accuracy that is in line with the engineering reality.By comparing with the simulation result of spindle rotation accuracy when ignoring the bearing temperature rise,revealing the importance of studying spindle rotation accuracy under the condition of bearing temperature.(4)Based on the established accurate simulation model of the controllable restrictor hydrostatic spindle rotation accuracy and the corresponding algorithm proposed,the effect of shaft roundness error on the controllable restrictor hydrostatic spindle rotation accuracy under the condition of bearing temperature rise was studied.The research shows that the controllable restrictor hydrostatic spindle rotation accuracy at the even-numbered frequency of shaft roundness error is significantly better than the odd-numbered frequency.Moreover,the spindle rotation accuracy is worst when the journal roundness error frequency is 1 wave/cycle;The increase of the shaft roundness error amplitude leads to the decrease of the spindle rotation accuracy.(5)On the basis of the controllable restrictor hydrostatic electric spindle prototype,a hydrostatic electric spindle rotation accuracy test experimental platform was built to measure the rotation accuracy.By measuring the rotation accuracy of the electric spindle under different oil supply pressure and speed,and comparing with the theoretical calculation results under the same conditions,the validity of the theoretical models and algorithms proposed in this paper are verified.This paper considers the influence of bearing temperature on the rotation accuracy of spindle,realizes the accurate simulation of the controllable restrictor hydrostatic spindle rotation accuracy,and improves the accuracy of the theoretical study of the spindle rotation accuracy.