Multi-degree-of-freedom Turning Chatter And Reliability Analysis

Because the ball screw has the characteristics of reliable work and high positioning accuracy,the ball screw is widely used in the feed system of CNC machine tools.The modal characteristics of the feed system have a crucial impact on the cutting performance of the entire CNC machine tool.At present,the research on turning flutter mainly focuses on the stability of turning flutter with one degree of freedom.Therefore,this paper comprehensively considers the parts of the feed system to establish the mechanical model of multi-degree of freedom of turning flutter.The main research contents include:(1)Based on the energy method,the dynamic model of feed system was established.The entire feed system as a linear time invariant system,adopt the method of focus on quality and distribution of quality,the quality of screw is considered to be evenly distributed Timoshenko beam,and the bearing and the screw,nut and screw contact as spring damping system,finally consider the direction of the axial and torsional deformation of a ball screw feed mixing system dynamic model is established.According to the dynamic equation,the modal mode of the screw and the natural frequency of the system are analyzed,and the influence of the dynamic parameters on the modal mode of the screw and the natural frequency of the system is analyzed.Finally,the accuracy of the dynamic modeling is verified by the natural frequency test.(2)Based on the regenerative flutter mechanism of turning,the mechanical model of multi-degree-of-freedom turning flutter was established.In this paper,considering the effect of regenerative cutting chatter force more degrees of freedom cutting chatter vibration mechanics model is established,by Laplace transformation,system characteristic equation is determined,and finally the Nyquist criterion as stability criterion,the analysis of the flutter stability,turning processing system and end up with spindle speed limit of cutting depth stability lobes diagram,used to predict metal cutting processing of flutter,flutter and the single degree of freedom and multi degree of freedom vibration mechanics model is analyzed,and then consider random feed system parameters on the flutter stability of the turning processing.(3)Based on the reliability theory,the reliability of flutter stability in turning is analyzed.The function state function was determined according to the expression of limit cutting depth,and then the flutter dynamic reliability was analyzed by using the fourth-order moment simulation method,and the reliability of the flutter stability of the turning system was calculated.Finally,Monte Carlo simulation method was used for verification.Finally,the influence of the random parameters of the feed system on the reliability sensitivity of the turning system is considered,and the random parameters which have the greatest influence on the reliability of the system are determined to provide a reference for the parameter design of the feed system of the machine tool.The dynamic model of feed system is established and the influence of dynamic parameters on the modal characteristics of feed system is analyzed.Considering the influence of cutting flutter force on turning,a multi-dof flutter mechanical model was established,and the influence of feed system random parameters on the flutter stability was analyzed.Reliability analysis and sensitivity analysis were carried out considering the influence of random parameter uncertainty factors.In this paper,modal analysis and flutter stability analysis of CNC machine tool feed system are carried out to provide theoretical reference for machine tool design parameters.