Reliability Modeling And Reliability Analysis Of Spindle System Of CNC Machine Tools

With the rapid development of manufacturing machining industry in China,the machining accuracy of the components of mechanical products is increasingly high;the machining quality of CNC machine tool directly influences the development speed of manufacturing machining industry in China.Spindle system as a work part of CNC machine tool,which directly or indirectly drives the work piece or tool,involved in cutting movement.The reliability of the spindle system directly affects the machining accuracy and machining efficiency of CNC machine tool.Therefore,it is very important to evaluate its reliability.Therefore,the reliability of the spindle system directly affects the machining accuracy and machining efficiency of the CNC machine tool,it is of great importance to the reliability modeling and reliability analysis of the spindle system.In this thesis,the spindle system of CNC machine tool is taken as the research object,the system reliability model is established,and the reliability analysis is carried out.The main contents are as follows:(1)The paper deals with the reliability modeling of the failure process of CNC machine tools whose failure intensity shows a bathtub type non-monotonic behavior,a reliability modeling of generalized Polya process is proposed.The preventive maintenance policies and mathematical details of the proposed model are also illustrated.Finally,combined with the field test data of CNC machine tools,a reliability modeling of generalized Polya process was built.Then the model evaluation criterion is given based on the index of goodness-of-fit test.(2)Based on the correlation theory of Copula function and the three-order conversion function of FMEA severity and failure frequency,the reliability allocation method of tandem system is established.According to the reliability requirement of the spindle system of CNC machine tool,the reliability allocation of the spindle system of CNC machine tool was studied,and the allocation reliability of each subsystem of the CNC machine spindle system was obtained.(3)Based on the influence of spindle deflection on machining accuracy,the reliability model of spindle system of CNC machine tool was established.The reliability sensitivity and reliability of the deflection are calculated by improving the second moment,Monte Carlo numerical simulation and perturbation method.(4)According to the design trend of the lightweight,with the minimum of quality and the lowest sensitivity of the parameters to the reliability as the design objective,a robust optimization model of the spindle structure parameters is established.The results are helpful to designers,manufacturers and users of spindle system.