Study On Consistency Control Of The Radial Gas Film Thickness Of Ultra Precision Aerostatic Bearings Based On Global Sizes

With the development of manufacturing industry toward ultra precision and precision direction,the application of precision aerostatic spindles is wider and wider.The thickness of the radial gas film has much influence on the characteristics of the aerostatic spindle,and for ensuring the stability of the characteristics of batch produced aerostatic spindles,the consistency control technology of the radial gas film thickness of ultra precision aerostatic spindles was studied in this thesis.The measurement method of global sizes using Talyrond 585 LT cylindricity measuring instrument and the standard ring was proposed,and the system error produced in the measurement of cylindrical roundness profiles using Talyrond 585 LT may be reduced through the calibration of the ring to transfer the extracted roundness profiles into the actual radial sizes between the sampling points to the rotary axis of the rotary table,so the extraction of cylindrical global sizes' features and the evaluation of their global sizes can be realized.The modeling method of the non-ideal cylindrical surface was studied based on profile measurement.The singularities in the cylindrical profiles were determined by using 3? criterion and replaced by using the linear interpolation method.The non-ideal cylindrical surface model was built by using Geomagic Studio software,and the precision analysis were done based on Geomagic Qualify software.The aerostatic bearing simulation model of non-ideal cylindrical surfaces was built by using UG software,and the model was meshed and its iterative resolution was done by using ANSYS WORKBENCH software.Ten groups of rotors and porous aerostatic bearings were selected as experimental objects,and the precision statistic analysis were done based on the non-ideal cylindrical surface models under the different sampling parameters and Geomagic Qualify and the better sampling parameters were gained.The simulation analyses of the bearing capacities and stiffness values were done based non-ideal cylindrical surfaces and global sizes,which under the better sampling parameters,respectively,and their stiffness values were tested on the modularization characteristic tester of the spindle.The simulation and testing results showed that for three combinations of global sizes of the rotor and bearing,such as combination of least-squares diameter of rotor and least-squares diameter of bearing,combination of minimum circumscribed diameter of rotor and maximum inscribed diameter of bearing and combination of minmax diameter of rotor and minimax diameter of bearing,the difference between the bearing capacities of the gas films formed by the combination of least-squares diameter of rotor and the least-squares diameter of bearing and the bearing capacities of the gas films formed by their corresponding non-ideal cylindrical surface of rotor and bearing is less,and the coincidence degree of stiffness values of the films formed by non-ideal surfaces and their corresponding test results is higher.Therefore,the modeling method of non-ideal cylindrical surfaces can provide the technique support for the realization of the stiffness evaluation under the non-ideal condition,and the gas film evaluation method of aerostatic spindles based on global sizes can also offer the technique support for the realization of the consistency control of the gas films in their batch production.