Research On Accuracy Analysis And Reconstruction Plan Of XD CNC Milling Machine

Machine tools have become one of the basic mechanical equipment in the manufacturing industry.Machining accuracy is one of the important indicators to measure whether the performance of machine tools is excellent or not,and it is the most important part of machine tool research.Because of wear and tear,the precision error of waste machine tools is large,and they are faced with being eliminated,resulting in great waste.The remanufacturing of scrap NC milling machine can not only effectively reduce the pollution to the surrounding environment,but also reuse some parts of the scrap milling machine.It can effectively restore the processing accuracy of the machine tool and improve the production efficiency,so as to realize the recycling of the scrap machine tool.In the past,the remanufacturing of machine tools mainly focused on the numerical control transformation of ordinary machine tools,which involved less in improving the accuracy of machine tools and increasing the accuracy retention time of machine tools.At present,it is a weak link in the remanufacturing of machine tools to improve the accuracy of machine tools and extend the accuracy retention.It is of great significance for NC machine tools to analyze and study the causes of accuracy errors of machine tools and to take effective measures to improve the accuracy of the analysis results.When the milling machine is working,the actual motion position of the table and the cutter will deviate from the ideal position.The smaller the deviation,the higher the accuracy.Based on the theory of multi-body system,the causes of accuracy error of NC milling machine are analyzed.The dimension error caused by wear of parts in NC milling machine is considered comprehensively.The motion relationship between parts is described by the transformation of homogeneous coordinate matrix.The precision mathematical model of NC milling machine is established.The sensitivity analysis model of wear parameters of parts is obtained,and each part is obtained.The weight ratio of Parts’ wear to machining errors of machine tools is analyzed.The main parts which havethe greatest impact on machining errors are analyzed to provide theoretical basis for the improvement scheme.Based on Hertz contact theory,contact stress and motion law of ball screw pair are analyzed.A prediction model of accuracy loss of ball screw pair is established by combining Archard wear model.Taking the ball screw pair equipped with XD NC milling machine as an example,the mathematical model is assigned to calculate the wear life of ball screw pair,and the running time of ball screw pair is predicted.According to the prediction model of accuracy retention,the prediction model is established.It predicts the accuracy maintenance life and the effective revolutions in the life time under normal working conditions,which can be used as a reference for the improvement scheme.The solid model of ball screw pair is established by using SOLIDWORKS three-dimensional modeling software,and the wear simulation analysis of the three-dimensional solid model is carried out by ANSYS Workbench finite element software.The influence of pre-tightening force on the wear of ball screw pair is compared,which provides a basis for choosing appropriate pre-tightening force.The wear amount and contact stress of ball,nut and screw are analyzed,and the cyclic stress is also analyzed.The fatigue life of the parts with the greatest wear is analyzed.In order to reduce the failure of pre-tightening force caused by wear,increase the axial clearance and decrease the accuracy,the original thread-type pre-tightening method of ball screw pair is changed to the tooth-difference pre-tightening method.Through the established mathematical model of accuracy loss prediction,the effective turning time of accuracy maintenance and effective time is predicted,and measures to improve accuracy are provided for the effective time of accuracy maintenance.The scheme is applied to increase the axial stiffness of ball screw pair,reduce the axial clearance and improve the accuracy.