| Nowadays,China's economy is developing faster and faster.As a common equipment used in manufacturing.CNC machine tools can represent a country's manufacturing level to a certain extent.Meanwhile,the processing technology of CNC machine tools is also one of the key technologies for the country's core competitiveness.In recent years of continuous development,China's industrial manufacturing industry is particularly rapid development.Mainly CNC machine tools play a very important role in promoting.Among them,the machining accuracy of a machine tool is one of the key indexes to measure the performance of a machine tool.It is mainly affected by the geometric error and thermal error of machine tools.So to improve the machining accuracy of machine tools has become a focus of attention of experts and scholars around the world.This paper selects the self-developed four axis precision CNC machine tool as the research object,conducts positioning error measurement,data collation and research analysis on its moving axes X and Z,and establishes the comprehensive error model of geometric error and thermal error.The main research contents of this paper are as following:(1)According to the multi-body system theory,the description method of the l ow-sequence array of the topology structure of the multi-body system theory is des cribed,and the multi-body system theory is analyzed and studied by mathematical modeling;At the same time,the motion between adjacent typical bodies is described.Error elements of moving shaft air,spindle error elements and perpendicularity error elements of the machine tool are analyzed.Based on the homogeneous coordinate t ransformation theory,the homogeneous transformation matrix of each kinematic chai n of the machine tool and the kinematic relationship between adjacent type bodies are derived in practice.(2)The measuring principle,composition and Chebyshev theory of laser interfer ometer is described.With self-developed precision four axis NC machine tool as the research object,using a laser interferometer to measure the four axis precision NC machine tools during cold moving axis X,Z axis positioning error value,analysis of measurement data,using the theory of cherished polynomial set up four axis pre cision NC machine tool moving axis X,Z axis of the geometric error model,the X,Z axis fitting out through analyzing the model,the curve fitting model and residual error between the actual machine tool geometric error model curve is lesser,s hows that the fitting effect is better.(3)Briefly describe the principle of decoupling and separation of the comprehensive positioning error of CNC machine tools and the comprehensive application of the theory of least square method.Xl-80 laser interferometer is used to evaluate,calculate and analyze the positioning error of the moving axis of the four axis precision CNC machine tool.At the same time,PT100 temperature sensor was used to measure the temperature change at the strategic position of the machine tool.Based on Chebyshev theory,the geometric reference error model of remote state is established.The variation rule between the positioning error and temperature change is found through analysis.The temperature change of the stator and the moving guide of the machine tool is selected as the thermal error modeling variable,and then the comprehensive error model of thermal error and geometric error of X and Z moving axes of the four-axis precision CNC machine tool is established by using the least square method and cherished polynomial theory.Through analysis,it is found that the residual error between the positioning error and the fitted comprehensive error model of the moving axis of the four axis precision NC machine tool is small,and the fitting effect is good.It is verified that the geometric and thermal error comprehensive error model established by the least square method and cherished polynomial theory has high prediction accuracy. |
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