| In the field of ultra-precision machining,the important factor affecting the accuracy of parts is the rotation error of the spindle of the machine tool.Researching the rotation error of the spindle of the ultra-precision machine tool can be used not only to evaluate the rotation characteristics of the spindle,to detect the operating state of the machine tool spindle,but also to estimate the machine tool The source of errors in machining parts can also provide a data source for the compensation of machining errors.The slow tool servo machining technology is widely used in free-form surface machining because of its advantages of large working stroke,large continuous and complex parts,high efficiency,and high precision.This article is mainly based on the Moore 450 ultra-precision lathe of the United States,and carries out related research on the main shaft rotation error of the lathe,and proposes a feasible online measurement method.In actual spindle measurement,indirect measurement is usually used: that is,by measuring standard components(balls or cylinders with high surface quality)installed on the spindle,the standard components are used as the measurement reference.In this process,the installation eccentricity error and roundness error of the standard part will be introduced.Therefore,the error separation method is required to separate the spindle error and the roundness error.The commonly used error separation methods include the inversion method,the multipoint method,and the three-point method..In order to achieve online measurement,the inversion method is used as the basis for error separation,and the error extraction process of the inversion method is simulated on Matlab.In order to reduce the influence of the eccentricity of the installation of the standard circle,the cylindrical workpiece obtained by rough machining is subjected to the secondary machining of the ultra-precision lathe as the measured standard circle.Then,according to the principle of the above-mentioned reversal method,an online measurement platform for the main shaft is designed and built.The main function is to realize the 180-degree reversal of the standard circle and the sensor,and it can collect the rotation angle of the main shaft in real time.This set of measurement fixture can measure with three sensors at the same time,and a fine-tuning structure is added to adjust the measurement position.After the temperature drift experiment,the stability of the fixture is ensured,and its rigidity meets the experimental requirements.The experimental measurement shows that the balance position of the spindle rotation error is different at different speeds,and the balance position is also different in different measurement states at the same speed,which further confirms the necessity of online measurement of spindle rotation error.After using the inversion method to obtain the original data of the two stations.The eccentricity error of the standard circle installation obtained by the Fourier analysis method and the least square method is compared and separated,and then the roundness error and the main axis error are extracted under the error separation algorithm of the inversion method.The roundness error is the roundness error of the standard circle,which reflects the surface shape error of the measured workpiece,which does not change with the change of the rotation speed.In order to better evaluate the characteristics of the spindle error at different speeds,the variation of the spindle error at several speeds was analyzed in the time and frequency domains.The main research result of this paper is to build a set of equipment that can be used for the online measurement of the spindle rotation error.The measuring fixture is designed based on the inversion method as the basic error separation method.After measurement and error extraction,the variation of spindle rotation error with speed is analyzed qualitatively,and the synchronous and asynchronous errors of spindle at different speeds are quantitatively evaluated. |
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