Simulation And Testing Of The Angular Stiffness Of The Aerostatic Main Shaft

For ultra-precision machining machine tools,the aerostatic spindle is the key to realize the precise rotary motion.Therefore,the performance of the aerostatic spindle has an important influence on the motion stability and machining quality of the ultra-precision machining tools.For a long time,the research and design of aerostatic spindle is mainly concentrated on the bearing,stiffness,rotation accuracy,and thermal stability.The insufficient study on anti-deflection ability of the spindle cause that it is difficult to improve comprehensive performance of aerostatic spindle.So the machining quality is hard to achieve desired results.According to the research status of aerostatic spindle at present,gas film pressure distribution simulation analysis programs are designed and deflection experiments are carried out to analyze angular stiffness of the T type aerostatic.Factors influencing the angular stiffness are discussed from theory and practice to explore the principle and variation of angular stiffness on aerostatic spindle.The main contents of this paper are as follows:(1)The principle of aerostatic bearing is analyzed,and the static pressure supporting model is constructed based on its boundary conditions as well as throttle method.At the same time,the relationship of the total deflection torque between the radial bearing and the thrust bearing of the T type aerostatic spindle is deduced.(2)The finite element method is used for dispersing and solving the Reynolds equation to obtain the aerostatic pressure distribution of gas film.Then the load bearing and the deflection moment of the whole shaft bearing can be acquired.As a result the cross scale and micro deflection problem of numerical simulation of the aerostatic pressure spindle is solved.The algorithm is programed with MATLAB language.The program is fast and efficient in simulation analysis of the aerostatic pressure distribution and computing the angular stiffness.(3)The single factor variable method is used to analyze the influencing factors of angular stifness of the aerostatic spindle.The variation curve of the angular stiffness is drew with the structure size,air pressure and other key factors,providing a theoretical basis for the aerostatic spindle's structure optimization design based on angular stiffness.(4)Exper:iments to measure the angular stiffness of a T-type aerostatic spindle are designed and implemented.The experiments work out the problem of precision measurement of the angular stiffness,verify the correctness of the support model and the finite element simulation analysis program,and reveal the important significance of the angular stiffness to evaluate the anti-deflection ability of the aerostatic spindle.Through numerical simulation and deflection experiments,this paper discusses the generating mechanism of aerostatic spindle's angular stiffness and analyzes the variation of angular stiffness with key factors.This paper provides the basis for structure optimization design of aerostatic spindle and a reference to improve its overall performance.