Chatter Stability Analysis And Chatter-free Cutting Control Of Mirror Milling Process

Mirror milling technology is proposed in recent years for processing large-sized thin floor parts such as aircraft skins which is environmentally friendly,efficient and has the tendency to replace the traditional chemical milling process.Chatter often occurs in mirror milling process leading to a decrease in the surface quality of the workpiece which limits a further application of mirror milling technology.This thesis theoretically studies chatter in the process of mirror milling process to provide guidance for practical production.The experimental system of mirror milling is set up.A three-dimensional dynamics model of mirror milling process is established according to the characteristics of mirror milling.Zero order approximation method is employed to solve the relationship between the chatter-free axial depth of cut and the spindle speed,and the chatter stability of the milling process is analyzed by plotting stability lobes.The effect of modal parameters such as natural frequency,damping ratio and the stiffness of machining area on milling stability in the mirror milling is analyzed.By setting up the stability prediction theory of mirror milling process,the theoretical basis for studying the stability limit variation during the process and the chatter-free cutting control method is laid.The theoretical modal analysis of the support-workpiece-clamping system is carried out.Through the finite element method,the modal shapes of five stages in the mirror milling process are calculated and analyzed.The milling force coefficients are obtained through experiments,the dynamic parameters of the cutting tool are obtained by impact tests and a non-contact measurement system equipped with a laser displacement sensor is set up to perform modal analysis.The modal parameters of the workpiece at different stages of the process are obtained,and the stability limits of the five stages in the process are predicted.The stability prediction results are verified through experiment.By the analysis of the machined surface,vibration displacement signal and the actual machining depth,the mechanism of chatter vibration in mirror milling process is revealed.According to the process characteristics of aircraft skin materials,a one-dimensional dynamic model of aircraft skin mirror milling processing is established.Modal parameters of the workpiece in different machining positions are obtained through finite element method analysis.Three-dimensional stability lobes are used to predict the chatter stability of the whole mirror milling process,and the prediction results are verified by experiments.A chatter-free cutting control method which employs variable cutting parameters in different stages during the process is proposed.Through cutting experiments,the accuracy of the proposed method is verified.