Research On The On-line Measurement Of Multi-degree-of-freedom Error Of Guideway

With the progress and development of modern science and technology,people have higher requirements for processing technology,especially for CNC machine tools and machining centers of machining and manufacturing accuracy.And geometric error of CNC machine tools(positioning error,horizontal and vertical straightness error,pitch error,yaw error and roll error)directly affect the machining accuracy of machine tool.And machine tool motion platform in the actual operating conditions by reason of load and no-load condition of different geometric error.Therefore,it is a necessary means to improve the machining accuracy of CNC machine tools to accurately and simultaneously detect and compensate the multi-degree-of-freedom errors of moving guide rail on line.At present,although there are many kinds of multi-degree-of-freedom simultaneous detection methods,most of the measurement methods have some shortcomings.Laser multi-degrees-of-freedom measurement system is unstable and difficult to install and debug because of its complex structure and many optical elements.Therefore,it is of great significance to propose an on-line measurement system for the geometric errors of multi-DOF with low manufacturing cost,high precision,strong anti-interference ability and easy operation.In this paper,based on the displacement detection principle of eddy current sensor,an online measurement system of multi-DOF geometric error of moving guide rail is proposed.At the same time,the error compensation model is established to compensate the errors caused by the measurement of five geometric errors caused by the flatness error of the datum plane,so as to ensure the accuracy of the measurement.A complete multi-DOF geometric error simultaneous measurement system is designed and built according to the principle of straightness and angle measurement.Positioning error can be measured by the machine itself.The geometric error of five-DOF geometric error can be measured simultaneously with the minimum number of displacement sensors by arranging the position of eddy current displacement sensor reasonably.Finally,based on Labview graphic editing software,the measurement system program is written in a modular way,including data acquisition module,filtering module,data processing module,data display module and data saving module.In order to verify whether the stability,repeatability and accuracy of the measurement system can meet the requirements of geometric error measurement of common machine tools.In this paper,the calibration experiment,stability experiment,repeatability experiment and comparison experiment of the measuring system are completed by means of displacement adjustment frame,digital display meter,laser interferometer,photoelectric autocollimator and electronic level.Experimental results show that the calibration residual of the eddy current displacement sensor of the system is less than ±0.42?m;repetitive residual error of straightness error of the system is less than 1.2?m,angle repeatability residual error is less than 1.8arcsec;the residual of straightness compared with the measurement results of laser interferometer method is less than ±1.4?m,the residual of yaw error and pitch error compared with the measurement results of photoelectric autocollimator are less than ±1.2arcsec and±1.6arcsec,the residual of roll error compared with the measurement results of electronic level method is less than ±1.5arcsec.The stability experiment shows that the system's straightness error within 30 minutes and 10 seconds is offset within 0.46?m and 0.7?m respectively,and the system's angle error within 30 minutes and 10 seconds is offset within0.75 arcsec and 0.19 arcsec respectively.The measurement results show that the system has reliable stability,high precision and good repeatability,and can meet the measurement requirements of common CNC machine tools.