Research On Error Model Of Contact Probe Of Three-Dimensional Thread Comprehensive Measuring Machine

In order to accurately measure the three-dimensional shape of thread,a three-dimensional thread comprehensive measuring machine is developed.As an important part of the three-dimensional thread measuring machine,the scanning probe undertakes the functions of aiming and measurement.Its accuracy is the key factor affecting the three-dimensional thread measuring machine,so it is necessary to study the probe error model.In this paper,the probe coupling error,geometric error and calibration model are studied,and the error model is verified by experiments.The main research contents are as follows:(1)Based on the structure of parallel reed probe,the key parameters of probe structure are optimized by COMSOL finite element simulation and orthogonal test method,including parallel reed ratio,rod length and needle radius.The linearity of probe under different structural dimensions is analyzed to determine the optimal structural parameters;(2)Due to the limited manufacturing accuracy and measurement principle,the probe produces coupling error during measurement.Therefore,the probe coupling error model under stress state is established by using material mechanics,the coupling error is simulated by COMSOL solid mechanics,and an experimental platform is built to verify the coupling error;(3)Aiming at the geometric error caused by installation and positioning error,the probe inclination error and thread positioning error are established by using the principle of spatial coordinate transformation,the probe radius compensation error is established by using the geometric principle,and the geometric error is verified by experiments.The model verification experiments of tilt error and thread positioning error show that the error after compensation is reduced by 68% and 77.5%respectively.The model verification experiment of radius compensation error shows that the error after compensation is reduced by 51% compared with that before compensation;(4)In the actual measurement,because the micro force mechanism is not orthogonal,that is,the coordinate axis of the probe is not orthogonal,and the coordinate axis of the probe does not coincide with the coordinate axis of the measuring machine,the probe calibration model is established by using the coordinate transformation principle and the least square method,and the screw ring gauge and plug gauge are measured by the three-dimensional thread measuring machine for verification.The experiment shows that the standard deviation of the parameters of thread gauge and ring gauge is about 1μm.