Analysis Of Guideway Precision Retention Based On Quasi-continuous Medium Method

Accuracy retention is one of the major technical bottlenecks restricting the research and development or import replacement of precision machine tools in China.Since the guide rail pair is the core component of precision machine tool feed system,it plays a decisive role in feed accuracy and maintainability.At present,the simulation and optimization of guide rail wear are based on the elasto-plastic mechanical model established by macroscopic assumptions such as continuum medium and isomorphism.However,due to fluctuations in the surface morphology of the friction surface,the longterm maintenance of guide rail accuracy is problematic.The micro-characteristics of the material itself,relying only on the material performance indicators defined by the macro-hypothesis conditions to describe accuracy losing process will have certain limitations.This paper aims to improve the accuracy retention of guideway,establishes the description model of the micro-convex body on the guideway surface,and realizes the description of the straight line precision loss process based on the Multi-scale judging method of the Quasi-Continuous medium principle.(1)The evolution process of microstructure and surface micro-topography of guideway pair is deduced,and the surface wear distribution of guideway is described systematically,which is the foundation of the research object of wear model and straightness precision.(2)A quasi-continuous medium method is used instead of the continuous medium,assuming that the wear pattern of the guide rail is constructed by combining the microscopic characteristics of the material and the constitutive equation to describe the wear process more accurately.The atomic partial wear exponent is presented to describe the deformation effect of the non-local atomic region of the guide rail to establish the wear exponent model by quasi-continuum method and the virtual work principle.(3)Based on the method of measuring the straightness of the guide rail,the measured value of the linear accuracy of the guide rail is systematically described.The linear precision test and measurement are performed using an XD laser interferometer,and the geometrical analysis is performed based on the exponential wear model of continuum medium.The exponential data correction of the measurement data confirms the self-consistency of the exponential wear model.(4)The linear accuracy retention model of both left and right guide rails of the linear motion experiment platform is calculated by using the logarithm method.The calculation results can reflect the deformation mechanism of the straightness of the guide rail,and it has reference value for the calculation of the accuracy of the failure life of the linear motion.(5)The method of Depth from defocus(DFD)is used to deal with the photo of the guideway surface obtained by high magnification optical microscope.The microtopography information of the guide rail is obtained to verified that the wear state of the guide rail during service,and it is provided verification that the rail exponential wear model under the principle of quasi continuous medium.