Influence Of Manufacturing Error On Static And Dynamic Characteristics Of Porous Aerostatic Bearings

Aerostatic bearing is an important supporting part of ultra precision machining machine,with the advantages of small friction loss,no pollution,high precision and long life.With the continuous development of ultra-precision technology,the requirement for bearing characteristics,slewing accuracy and stability requirements of aerostatic bearing are also rising.Porous aerostatic bearing has the advantages of good stability,high bearing capacity and better precision,and is gradually replacing the aerostatic bearing with orifice restrictors as the focus of domestic and foreign scholars.However,the influence of manufacturing error on the static and dynamic characteristics of porous gas hydrostatic bearing are the difficulties,which has to be solved to further improve the accuracy of ultra-precision machine tools.Based on the analysis of the theory and method of aerostatic bearing at home and abroad,this paper aims to explore the characterization method of manufacturing error of porous aerostatic spindle and the influence of manufacturing error on static and dynamic characteristics and its solution.The main contents of this paper are as follows:(1)A numerical method for solving the static and dynamic characteristics of porous aerostatic bearings has been changed.Based on the basic equations of fluid mechanics and the law of internal flow field of porous pores,the solving equation of porous aerostatic bearing is established.Based on the fluid mechanics software,the numerical solution model of porous aerostatic bearing is established,and the static and dynamic characteristics are solved which is based on the dynamic grid technology.The dynamic rotation accuracy prediction method of the bearing rotor is proposed.The rotational speed is transformed into the linear velocity and the Naiver-Stokes momentum source term is added to solve the problem of rotational motion grid distortion,achieving a dynamic simulation of the spindle movement process,which will help to promote the research work of the impact on aerostatic bearing;(2)The characterization method of manufacturing error and its influence on the static characteristics of porous aerostatic bearing are studied.Based on the combination of experimental and mathematical functions,different kinds of manufacturing errors are characterized,and embedded in the numerical model of bearing.The influence of different kind of manufacturing errors on the static characteristics of porous aerostatic bearing is calculated,and the relationship between the type and amplitude of manufacturing error on the radial and axial bearing capacity and stiffness is obtained.The static characteristic experiment verifies that the calculation result when considering the manufacturing error is closer to the real value.The above work will contribute to the structural design of porous gas hydrostatic bearings.(3)The influence of different manufacturing error on the dynamic characteristics of porous aerostatic bearing is analyzed.Based on the analysis of the rotational motion of the bearing rotor,the influence of the unbalance and the roundness error on the rotation accuracy is studied.By comparing the pressure distribution,the velocity vector and the bearing capacity of the bearing gap,the dynamic influence mechanism of the roundness error is analyzed when the manufacturing errors exist or not.By changing the influence of cylindrical error on the axial direction into force form,the dynamic grid technique is used to embed it into the axial solution equation,and its influence on the axial dynamic characteristics is obtained.Finally,the results of the rotary accuracy test verify the above conclusions,the research work will help to promote research work to the promotion of precision of the ultra-precision machine tool.