Analysis On Identification Of Machine Tool Geometric Errors In The Linear Motion Based On Composite Reference Element

With the rapid development of mechanical manufacturing,CNC(computer numerical control)machine tools cover a wide range of applications in the mold manufacturing industry,electronic engineering,and the automotive and aerospace industries.Owing to its advantages of being all-purpose with high precision and a large processing scope,it has become a very necessary type of equipment.Precision plays a key role in CNC machine tools,and this is a hot topic in the machining automation domain.In order to improve the accuracy of the linear motion of CNC machine tools,this article proposed an innovative measuring system based on composite reference elements and applied this system to identify geometric errors of a machine tool.The main works are as follows:1.On the basis of analysis on character of plane mirrors and revolutionary paraboloid mirrors,a multi-degree-of-freedom measurement system composed of plane mirrors,revolutionary paraboloid mirrors and an angle sensor was designed.2.The design and optimization of the optical path of the angle sensor were conducted.When the angle sensor measures the plane mirror and the rotating paraboloid mirror,the readings are all within 0.3 arcsecs and 0.2μm respectively.And the relative angle calibration method of the plane mirror of each target was proposed.Based on the geometric property of the feature point of a target,the relative position calibration method of the feature point of each target was presented.3.Taking a three-axis machine tool as example,the identification method of geometric errors of the machine tool was proposed,which is conducted through measuring the composite reference elements located horizontally and vertically by the angle sensor driven by the machine.According to the preset path,the relative angle and position of each target are measured.In addition,the geometric error of the machine tool in linear motion can be measured based on the measurement values and calibration values of each target.4.With the experimental platform established on a three-axis machine tool,the calibration experiment of composite reference elements and the geometric error identification of machine tool were conducted.Through comparing the identification result of the measurement system and that of a laser interferometer,the feasibility and precision of the measurement system were verified and the influence factor of precision were analyzed.Compared with the laser interferometer,in 500 mm straight travel range of machine tools the average identification error of angle error is less than ±1 arcsec,and the average identification error of position error is less than ±1.5 μm.Besides,the height and time stability of the measurement system were tested by practical experiments.