Research On The Multi-point Multi-step Pressure Straightening Technology Of Linear Guides

Linear guide is the key component of linear motion system for CNC machines and automatic machines.Therefore,the improvement of the accuracy of linear guide is imperative with the increased requirement of the accuracy of linear motion.Straightening,the key process for the manufacture of linear guide,can reduce the machining allowance and guarantee the uniform distribution of quenched region,improving the surface quality,abrasive resistance and service life.The three-point straightening process is the preferred straightening method right now.However,there is a large error when applying single-step straightening method on some straightening cases.As a result,the research on the multi-step straightening process of linear guide is very imperative.Based on the theoretical and experimental research of multi-step pressure straightening technology for the linear guide,the main contents of this article are shown as follows:(1)The curvature-moment theoretical model for the straightening process of linear guide has been established,revealing the bending mechanism in the straightening process.The stress,strain and moment with the variation of bending curvature in the straightening process are calculated following by the continuous assumption.Considering the different constitutive models of the materials,the influences of the material parameters and anisotropy characteristics on the straightening principle has been analyzed,which is the theoretical basis for the research of span-straightening stroke model.(2)The span-straightening stroke model has been proposed for the straightening of linear guide.In order to improve the accuracy and integrality of theoretical model the analytical model about the angle of rotation and deflection is established by the integration method of curvature based on the relationship between the curvature and the deflection during bending process.Then,the straightening stroke is accurately predicted regarding the typical material models,as well as the related straightening parameters.Finally,the proposed model is validated by the three-point bending experiments of linear guides.(3)The mathematical model of the multi-step straightening process is proposed by using the discrete coupled method.Firstly,the coordinate system is defined to describe the multi-step pressure straightening process.Normally,the straightening points are discretely distributed along the lengthwise direction of linear guides.Considering the variation of deflection curve caused by the rotation of angle and deflection in every single-step straightening,the mathematical model of the multi-step straightening process has been established,describing the variation of deflection curve during the straightening process.(4)The straightening strategies and the setting method of straightening parameters are designed in this thesis.In order to guarantee the accuracy of multi-step straightening process,the fixed-step multistep straightening strategy is first proposed for the single-arc linear guide with long length or large initial deflection.Then,based on the boundary conditions generated by the theoretical model,actual straightening conditions and the shape of initial deflection,the variable-step multistep straightening strategy is designed for the linear guide with complex shape.To improve the straightening accuracy and efficiency,the optimization of straightening parameters is realized by using the Bees algorithm.(5)The online straightening system is built to control the straightness of linear guide and conduct the straightening experiments.Firstly,the fast recognition algorithm of the material parameters is realized considering the uncertainty errors generated by the material models.In order to improve the straightening accuracy,the online control strategy is proposed for the real-time control of straightness.It can realize the online compensation of material parameters,and the planning or replanting of the straightening parameters.Finally,the theoretical model of multi-step pressure straightening process is validated by the straightening experiments of linear guides on the proprietary straightening machine.