| The on-machine measuring system of CNC machine tools can perform most of the measurement work in one machine with one clamping,and is widely used in production.The main error elements include machine geometry error,grating measurement system error,probe system error,workpiece error,measurement strategy error,and error caused by data evaluation method.The error of the on-machine measurement system is not the simple linear addition of the error elements,but the influence of the error dynamics and correlation under the action of different objects,different strategies and many influence elements.Therefore,it is necessary to comprehensively study the experimental device for measuring the dynamics and correlation of the error in the machine.The existing experimental equipment unable to meet the requirements of carrying out the correlation error test.Therefore,this paper develops the experimental platform of the correlation error of the CNC machine tool in the machine with the stacked XY table.The purpose is to use the XY table as a theoretical prototype to carry out the verification method of the critical point of thermal deformation of the XY table and the instantaneous motion center of the table.Finally,the research results are transplanted to the CNC machine.The main work carried out in this paper is as follows:(1)Determine the design specifications of the test bench hardware,control circuit,test system,and plan the functions of each subsystem.Design the mechanical structure of XY table,marble base and temperature control cover;design the thermal deformation critical point and the measurement error of the comprehensive error test;design the control circuit to realize the servo motor running according to the requirements,the temperature control cover precisely controls the temperature,design the sensor of the test system The circuit develops a data acquisition program based on virtual instruments.(2)Calorific value and convective heat transfer of main friction components are calculated theoretically to provide theoretical basis for the boundary conditions of finite element simulation analysis.A finite element model is established by using ANSYS Workbench software to simulate and analyze the transient and steady temperature field distribution of rolling linear guideway and ball screw.The temperature field measurement test is carried out to realize the temperature field measurement function of XY worktable,in which the temperature rise of the screw nut is the largest,and the temperature rise is about 8 ℃.(3)The performance test of the experimental device is carried out,and the high-speed,low-speed,forward and backward feeding test of the XY worktable is carried out to meet the maximum 20 m/min and the minimum 0.05 m/min forward and backward feeding.After the machine tool is preheated for 4 hours,the positioning error,pitch angle error and yaw angle error of the X-axis and Y-axis at different speeds are measured by laser interferometer to verify the stability and repeatability of the accuracy of the worktable.The maximum repetitive positioning error of X-axis is 3.96 μm,and that of Y-axis is 1.56 μm. |
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