| As the industrial mother machine of modern manufacturing,computer numerical controlled(CNC)machine tool is an important symbol for the level of national assembly manufacturing industry.Machining accuracy is a key index of the machine tool.Error compensation is a main way and development trend to improve and maintain the machining accuracy of CNC machine tools.The quick and high-precision measurement of various errors of CNC machine tools is the premise and key for error compensation.Linear axis,which is the key moving part of CNC machine tool,has 6degree-of-freedom(6DOF)geometric errors,and three axes of CNC machine tool have21 geometric errors.How to realize the quick and high-precision measurement of 21 geometric errors has become an urgent problem and a research focus to be solved for the error compensation of CNC machine tools.In response to the above problems,this thesis,funded by the National Natural Science Foundation of the China-Major Program,and based on our group’s long-term research on the simultaneous measurement of 6DOF geometric errors of single linear axis,a one-step installation and three-step measurement method for fast,accurately and directly measuring 21 geometric errors of three linear axes of CNC machine tools is proposed innovatively.The unified measurement model of 21 geometric errors is established and the corresponding measurement system is developed.The effectiveness and reliability of the measurement system are verified by a series of laboratory and on-site experiments.The primary job and innovations of this dissertation are as follows:(1)A fast and high-precision method for directly measuring 21 geometric errors of three linear axes of machine tools is proposed.A one-step installation and three-step measurement method for 21 geometric errors of three linear axes of machine tools is proposed.All 21 geometric errors of three linear axes of machine tool can be measured automatically,quickly and accurately only with one-step installation.Compared with a single-parameter laser interferometer,it not only improves the measurement efficiency,but also reduces the adjustment error caused by multiple installation and adjustment and the measurement error caused by long-time measurement environment change.The comprehensive accuracy of measurement is improved.(2)A unified measurement model for 21 geometric errors of three linear axes of different types of machine tools is established,and the universality of the measurement method is realized.The measurement methods for four types of CNC machine tools are standardized into two measurement modes.The influences of 6 installation errors of detectors and the installation errors of 18-error sensing prism are analyzed,and the6 DOF geometric error measurement models of single linear axis are established for two measurement modes,respectively.On this basis,a unified measurement model of 21 geometric errors is established by analyzing the influence of the installation and the manufacture errors of the beam-steering device on the measurement.The correctness of the model is verified by Zemax simulation and experiment.(3)An beam-steering device and a 18-error sensing prism are invented and a quick,high-precision and direct measurement system for 21 geometric errors of three linear axes of CNC machine tools is developed with the optical,signal processing circuit,and measurement software design.A series of experiments are carried out,and the results show that the measurement repeatability errors for straightness,yaw and pitch,roll,and squareness are ±0.5μm,±0.5″,±1.5″,and ±0.6″,respectively.Compared with a single-parameter laser interferometer and electronic level,the deviations are ±0.7μm,±0.5″,±1.0″,±1.6″ respectively,and the measurement efficiency is increased by 45 times.(4)The application researches on improving the machining accuracy of CNC machine tool and compensation effect are carried out.In order to improve the machining accuracy of machine tool,the spatial position error distribution is analyzed,and the key geometric error elements which have great influence on the spatial position accuracy are obtained.In the on-site measurement and compensation of 21 geometric errors of the three linear axes of a large gantry machine tool,the measurement process has been completed by the measurement system within 10 min,which greatly improves the measurement efficiency and achieves a higher on-site measurement accuracy.Additionally,based on the positioning error measurement results of three linear axes obtained by the measurement system,the error compensation has been performed to the machine tool,and the appraisal results,which are tested by the National Intelligent Manufacturing Equipment Product Quality Supervision & Inspection Center(zhejiang),show that the positioning accuracy of the X and Y axis has been improved by 76% and79% after error compensation,respectively,which leads to a good compensation effect.The developed measurement system has been successfully applied. |
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