Thin-walled Workpiece Machining Stability Domain Modeling And Chatter Monitoring Method Research

Thin-walled parts are widely used in the aviation,aerospace,petroleum,chemical and pharmaceutical fields.Thin-walled parts are recognized as hard to machine,the workpiece shape is complex,existing the problem of high material removal rate,low rigidity and poor manufacturability.Under the influence of cutting force,cutting chatter and so on,the workpiece is easy to deform,vibrate or instability in the machining process.Taking the conservative processing technology,the production efficiency is greatly reduced.With the development of advanced science theory and advancement of manufacturing technology,higher requirements for the stability,efficiency and reliability of thin-walled parts in high speed machining are put forward.As the existing problems in thin-walled parts machining,this paper studied relevant research about milling chatter mechanism,thin-walled parts dynamic characteristics in machining,machining parameters optimization,and chatter monitoring.Main contents are as follows:(1)The vibration types in milling is classified from excitation source control modes,vibration response types and system's opposite properties three aspects,the chatter mechanism of three kinds is explained,which influences much to machine.The influence factors of chatter are summarized,it is stated about the domestic and foreign scholars' research on chatter phenomenon suppression and monitoring at the same time.(2)The motion analysis of the milling system is analyzed,the calculation theory of stability lobes diagram is explained.The program parameters are changed and calculated,the lobe trend is studied and we made the corresponding analysis.The milling coefficients of the selected tools and materials is calculated through the milling experimental data and the vertical milling cutter force model.Thin-walled workpiece is processed by six layers,then we can get the modal parameters through experiments after each layer machined.The three dimensional stability domain lobe is calculated,taking into account of the machining position.(3)We studied the chatter phenomenon existing in machining,chose the sound pressure signal to feedback the chatter characteristics.The sound pressure data of the machining center is collected,time domain and frequency domain characteristics are observed at the same time.It's found that when chatter occurred,the time-domain RMS amplitude increased sharply,the frequency domain excitation frequency shifted from the shaft frequency to the first order natural frequency of the tool-spindle subsystem,frequency-domain energy concentrated bands shifted from low frequency band to high frequency bands.We came up a characteristic 4),which can reflect the frequency energy feature,RMS,percentage of cared frequency bands,characteristics 4)are chosen to judge the chatter phenomenon.(4)The complete discretization algorithm is compiled into an executable program through the LabVIEW software,which can simplify the stability lobe diagram calculation procedure.According to the chatter data features,the monitor scheme is proposed based on multi characteristics and constructed as the monitoring on-line system,which can collect,store,analysis the vibration data in machining,to achieve the destination of chatter monitoring.