Research On Dynamics And Reliability Of Spindle System Of CNC Machine Tool

As the basic tool of modern equipment manufacturing industry,Computerized Numerical Control(CNC)machine tool is developing in the direction of high efficiency,high speed,high precision and high reliability.As the key subsystems of the CNC machine tools,the dynamic characteristics and reliability of spindle bearing system will directly affect the performance of CNC machine tools.Therefore,this paper takes the spindle system of a certain type CNC lathe as the object,and studies its dynamic characteristics and reliability.The main work of this paper is summarized as follows:In order to prevent resonance,the spindle system needs the modal analysis.In this paper,the spindle system is simplified and then the transfer matrix method is used to solve the first-order natural frequency and critical speed of the system.The ANSYS finite element software was used to simulate the spindle system,which verifies the accuracy of the transfer matrix method.In the spindle system,the spindle system becomes a strong nonlinear system due to the existence of radial clearance and non-linear Hertz contact force in the rolling bearing,as well as the unbalanced force of the spindle system.In this paper,a nonlinear dynamic analysis model of ten-degree-of-freedom spindle system is established by using the lumped mass method.The dynamic response of the system is obtained by Runge-Kutta numerical integration method.The nonlinear dynamic characteristics of the spindle system are analyzed by the bifurcation diagram,time domain diagram,frequency domain diagram,phase diagram and Poincare diagram.The influence of different design parameters on its nonlinear dynamic characteristics is obtained.The researches provide a theoretical basis for improving the dynamic performance of the spindle system.Due to the random uncertainties in the design and manufacture of the spindle system,the reliability analysis of the spindle system is needed.However,the spindle system is a strong nonlinear system,and it has an implicit performance function,so the general method is difficult to assess the reliability of such problems.Therefore,a reliability evaluation method based on Kriging model and Monte Carlo method is used in this paper.And the U-learning function is used to optimize the model to obtain a sufficiently accurate Kriging model.Finally,the reliability of the spindle system is analyzed,and the sensitivity of the spindle system reliability to each basic variable is analyzed.The researches provide a theoretical basis for the reliability design and optimization of the spindle system.