| The ultra-precision processing technology can meet the requirements of machining accuracy with the rapid development of industrial manufacturing technology and the quality requirements of product processing have been continuously improved.It is an important content of the development of modern science and technology,which affecting the development of modern processing industry.The aerostatic spindle is one of the core components of ultra-precision machining equipment,and has the advantages of fast speed,high precision,small friction,low loss and so on.The ultra-precision aerostatic spindle is prone to run-out and unbalanced response when the speed reaches tens of thousands of revolution,and the surface of the machine is damaged and the processing requirements cannot be met.In order to solve the above problems,taking high speed ultra-precision aerostatic spindle as the research object,to improve the critical revolution speed and stability of aerostatic spindle by studying the structure and performance of aerostatic spindle,and offer the reference to further research of ultra-precision machining technology.The main contents are as follows:(1)The basic form and steady state equation of gas lubrication Reynolds equation are calculated and derived and the spindle film thickness and orifice hole mass flow are given,according to the equation of gas flow motion,continuity equation and state equation of the theory of gas lubrication.The gas film pressure distribution,bearing capacity and stiffness of aerostatic spindle(traditional aerostatic spindle)of homogeneous distribution and invariable diameter orifices are obtained,which using the finite difference method to solve the steady state Reynolds equation and write the calculation program by MATLAB software.In order to solve the problem of slow speed of Reynolds equation by finite difference method,a new solution method is proposed which to reduce the number of iterations and improve the calculation efficiency by simplifying the calculation of orifices hole mass flow.(2)In order to improve the performance and stability of the aerostatic spindle and optimizes the structure design of the traditional aerostatic spindle,furthermore,a new aerostatic spindle restricted by inhomogeneous distribution and variable diameter orifices was proposed.When the spindle speed is 0 and 40000r/min,the design parameters such as orifices diameter,supply pressure,eccentricity ratio and attitude angle have influence on the loading capacity and stiffness performance of the aerostatic spindle.Through comparison and analysis,when the spindle is stationary or moving,the loading capacity and stiffness of the new aerostatic spindle are significantly improved than those of the traditional aerostatic spindle.And the loading capacity and stiffness are enhanced by increasing supply pressure and eccentricity ratio,decreasing orifices diameter,choosing appropriate average gas film and the location of orifices.(3)The dynamic characteristic coefficient is the basic condition for analyzing the phenomenon of run-out and vibration during spindle motion,and the dynamic stiffness coefficient,dynamic damping coefficient and dynamic equation form of are studied to study the dynamic.The influence of the design parameters such as spindle mass,rotational speed and damping coefficient of spindle on the center of mass and centroid motion of aerostatic spindle is obtained by solving and analyzing the differential equation of spindle motion with the cylindrical vortex of aerostatic spindle as the dynamic research content.It is concluded that the speed and the spindle stability can be improved by selecting the proper spindle mass and damping coefficient.(4)In view of the fact that the gas film flow field cannot be obtained in the mathematical calculation of aerostatic spindle.The gas pressure distribution and velocity distribution at the film gap and orifices hole on the surface of the spindle are obtained by the research model of aerostatic spindle is pre-processed,solved and post-processed based on the fluid simulation software,in order to study the flow field characteristics at the film gap on the surface of the spindle.The correctness of the theoretical analysis of the static characteristics of the aerostatic spindle is verified,through the analysis of the gas pressure and velocity of the spindle surface,and which provides an important reference for the study of the static and dynamic characteristics of the aerostatic spindle.Summary:The results show that the performance of the new aerostatic spindle is obviously better than that of the traditional aerostatic spindle by the theoretical research,structural design,performance analysis and simulation analysis of aerostatic spindle,which provides an important reference for the research of ultra-precision machining technology.The new method which is proposed for solving Reynolds equation significantly reduce the number of iterations and improve the calculation efficiency,and provide reference for further speeding up the solution of Reynolds equation. |
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