Research On Sphericity Measurement Method And Equipment Of Bearing Balls Based On Weft Method

High precision bearing balls are widely used in linear bearing,ball screw,bearing and other products.The sphericity error of bearing balls is the main cause of lowfrequency vibration.The current specialized measuring method for sphericity error of bearing balls is mainly assessed by measuring the three mutually perpendicular crosssections,which has high measuring efficiency and tiny range and needs rotate many times in order to measure different positions.However in the universal sphericity measured method,the datum variation error is generally existed.Therefore,this paper focuses on the high-precision sphericity measurement for bearing balls and studies the measurement method which is suitable for the sphericity measurement of bearing balls and take the measurement efficiency and accuracy into account.The main contents of this paper are as follows:In order to achieve high accuracy and efficiency,a non-contact weft method was proposed to measure the sphericity of bearing balls.Robust gaussian filtering was used to filter the measured data and reduce the influence of abnormal signals on the measured results.The evaluation methods of the sphericity which included minimum leastsquares,minimun zone,minimun circumscribed sphere and maximum inscribed sphere were derived.The influence containing 25 geometric error terms of the non-contact weft method on the measurement results was studied.6 main error terms with great influence on the measurement results were obtained by analyzing the measurement model which was established through homogeneous coordinate transformation.Sphericity measurement instrument for high precision bearing balls was developed based on the measurement method.In order to improve the straightness,the vertical axis structure of aerostatic bearing was designed,and the simulation analysis of gas film and flexible screw nuts was carried out.Aiming at high precision,high acquisition frequency and measuring ability of curved surface,high precision measuring sensors were selected.In order to location the bearing ball quickly,a tapered fixture was developed.The accuracy of the mechanical system was estimated to meet the design requirements.Based on the imac-fxv2 motion controller,the electric control system was designed and debugged.The program is writed by MATLAB and C++.The rotary accuracy of the aerostatic bearing was measured by the inductive micrometer and the straightness of the vertical axis with aerostatic bearing was detected by the photoelectric autocollimation instrument.Single cross-sections roundness of the bearing ball was measured.The sphericity measurement experiment was carried out on a 12 mm bearing ball which verified the accuracy of the sphericity measurement method.The error of sphericity was 78.050 nm by the method which measured the three mutually perpendicular cross-sections which verified the feasibility of the sphericity measurement method.