Mechanism Analysis Of Assembly Error Transmission And Homogenization Of Linear Rolling Guide

Based on the theory of multi-body system,establishing the mapping model of toolworkpiece relative pose error and geometric error source for NC machine tools is a frontier common technology to realize tolerance allocation of machine tool structural parts,selection of rolling guides and support bearings.The bottleneck problem is how to construct the error transfer relationship between the mounting surface of rolling guide and the motion pair considering the rigid-elastic displacement coupling,that is,the error homogenization coefficient.This paper closely combines with the research task of the national CNC machine tool science and technology major special subject.The error transfer mechanism of linear rolling guide pair and the method of constructing error mapping law between installation surface and motion pair of rolling guide are mainly studied.Combining simulation with experimental analysis,the error equalization coefficient is quantitatively determined which lays a theoretical foundation for truly realizing the overall geometric precision matching design and assembly process error optimization of CNC machine tools.Based on Hertz contact theory,the empirical formulas of contact deformation and contact pressure of rolling body are deduced.The mechanical analysis of single slider is carried out,and the bearing capacity of single slider is solved.The transfer function model of bearing capacity and geometric error of single slider is established.Based on the force and moment balance equation of four slider rolling guide pairs and the relationship between slider deformation and worktable deformation,the mapping model of position and attitude error of worktable and geometric error of guideway is constructed.The definition method of error homogenization coefficient is proposed,and the mechanism of error homogenization is revealed by taking the normal straightness error as an example.On the basis of the above theoretical analysis and the spring element method in finite element method,the simulation analysis model of guide-worktable is constructed,and the simulation analysis of the worktable stiffness,slider stiffness,guideway pair span,uniform load,preload,external force and geometric error shape which affect the error homogenization is carried out.The relative position of bolt and waveform errors and the error frequency of base plane which affect error transfer of the guideway base surface-guideway finite element model are simulated and analyzed.Based on correlation analysis and nonlinear regression analysis,the relationship between the homogenization coefficient and the geometric error coefficient of the guide rail is fitted.To verify the influence of wavelength on homogenization,an experimental platform for error homogenization of rolling guideway pairs is built.Three groups of error homogenization experiments are designed.The straightness error of rolling guide pair is detected and the error homogenization coefficient is calculated.Compared with the simulation results,the conclusion that the experimental results and simulation results are less than 20% is drawn,which verifies the correctness of theoretical analysis and simulation analysis.