Study On The Guide Rail Contact Characteristics And Motion Errors In CNC Machine Tools

The performance of the CNC machine tool feed system depends on the manufacturing accuracy of each part on the one hand,and also depends on the assembly accuracy of each part on the other.As one of the key parts constituting the feed system,the manufacturing and installation accuracy of the guide rail is the basis for ensuring the relative assembly accuracy and movement accuracy of the main components in the feed system,which will most directly affect the movement attitude of the table,and furthermore It is called one of the main factors affecting the shape error and position error of the workpiece.As one of the most direct factors affecting the workbench,the guide rail pair lacks a complete and systematic method to evaluate the effect of the guide rail error on the motion error of the workbench.Therefore,a static model of the guide rail pair of the CNC machine tool and the workbench after considering the guide rail error are established.The motion system error model is used to analyze the effect of the guide rail error on the motion posture of the table.It has important theoretical significance and practical application value in improving the assembly and processing accuracy of CNC machine tools and optimizing the error allocation in product design.This article first establishes a single-slider model of the LM rolling guide pair,and then builds a simulation structure of the dual-rail,four-slider table motion system based on this,and considers the error model of the influence of the guide rail error.The specific content is as follows:(1)Judging the deformation and contact state of the ball by describing the change in the center of curvature of the slider and the guide rail,determining the reaction force on the table,deriving the mechanical balance equation of the slider body,and establishing the quasi-static mechanics of the contact of the single slider ball guide Model;through numerical analysis,the effects of pre-tightening force and initial design contact angle on the contact characteristics of the single-slider guide pair were proved.(2)Using the coordinate transformation theory,the relative positional relationship expression between the curvature center of the contact point of the guide rail and the slider and the motion error of the table is deduced,and a quasi-static mechanical model of the contact of the dual-rail four-slide table motion system is established;Using the Newton-Raphson algorithm,a Matlab solution calculation program was written.Through numerical calculations,the influence of external system load on the table motion error was proved,and a quantitative criterion for ball preload failure was proposed.(3)The parallelism error of the guide rail is divided into horizontal error and vertical error;through numerical calculation,the influence of various types of guide rail parallelism error on the table movement error is systematically analyzed,and the horizontal and vertical parallelism of the guide rail is proved.The relationship between errors and errors of the table motion system,the concept of error transfer coefficients is proposed,and the transfer coefficients of the five motion errors of the table in the horizontal and vertical directions are given,which reveals the original error of the feed system to the work motion error.Impact mechanism.(4)Through numerical analysis,the influence rule of the geometric manufacturing error of the guide rail on the table motion error was proved.Taking typical arched geometric errors and sinusoidal geometric errors as examples,the transfer coefficients of the differences between the geometric errors of the two guide rails to the errors of each motion system of the table are calculated;and the sinusoidal waveform errors are taken as examples to further analyze the wavelengths of the geometric errors of the guide rails,Amplitude and phase affect the motion error transfer coefficient of the table.