Error Analysis And Compensation Of Compound Machine Tool

In the competition of national industrial technology level,the development and innovation of high-end processing equipment,such as compound processing machine tools,processing centers,precision or ultra precision CNC machine tools,is the top priority of national development.As the most important technical index of CNC machine tools,machining accuracy directly determines the quality of products.Although some machining errors will inevitably appear in machining,the effect of "accuracy evolution" can be achieved through error compensation.In this thesis,the compound machine tool is taken as the research object,and the scientific research is carried out from error analysis,measurement,modeling and compensation.The main work is as follows:(1)This thesis describes the structure of the compound machining machine tool studied in this thesis,analyzes the error sources and classifies the errors of the machine tool,and then takes the translation pair,rotation pair,three coordinate axis and machine tool spindle as examples to analyze the error elements,and finally combs out the comprehensive error elements of the compound machine tool.(2)This thesis expounds the measuring principle of geometric error elements of compound machining machine tool,introduces renishawXL-80 laser interferometer,and explains the measuring principle,straightness measurement,angle measurement,linear displacement measurement and perpendicularity measurement.Then,taking the positive stroke of axis X of machine tool as an example,this thesis studies and analyzes the positioning error of this axis in the process of machining.In the process of machining,the internal and external parts of machine tool are analyzed.The change of environment temperature has a certain influence on its X-axis.Therefore,PT100 temperature sensor is used to measure the temperature change of key points,renishawXL-80 laser interferometer is used to measure the geometric positioning error,and displacement sensor is used to measure the displacement error of key points.After measuring the data,the mathematical model of spatial positioning error is established based on the least square multiple linear regression method.(3)The improved k-mediods algorithm and grey correlation method are used to optimize the temperature variables and determine the heat sensitive points.The thermal error model of the machine tool spindle is established based on the multiple linear regression method of the least square.The experiment shows that the number of temperature measuring points is reduced from 17 to 4,and the axial thermal error of the machine tool spindle is reduced from 35.9 ?m to 6.1 ?m.In addition,through thecomparison between the experimental data and the predicted value of the model,the residual error is small,which indicates that the thermal error model has good prediction accuracy.(4)From the angle of error compensation,the research on reducing the machining error of compound machining machine tool is carried out.By using the openness of PMAC system,the error mathematical model is directly embedded in CNC machining program,so that the program can be updated dynamically,the compensation value can be analyzed in real time,and the error can be compensated by feedback to servo system through PMAC control card.