Research On Improved Full Discretization Method For Milling Stability Of Thin-Walled Parts

Milling often used in aviation,aerospace,marine,automotive and other fields in the production of various parts,is one of the important basic technology for complex shape curved surface.At present,the two hotspots in the field of milling are the dynamic modeling and stability analysis of milling process.Machine tool in the process of milling,the chatter caused by the uneven thickness of adjacent two cutting process,which greatly reduces the quality of surface machining parts,and the tool life will be affected.In particular,the processing of thin-walled parts,due to its low stiffness,time-varying dynamic characteristics,easily happened chatter,is a major milling problem.Therefore,the study of the stability of the milling process can reveal the combination of process parameters(spindle speed and depth of cut)in order to avoid flutter to achieve the goal of improving cutting efficiency and maintaining machining accuracy.(1)This thesis,starting from in-depth researching on cutting thickness model,the change of the thickness of the cutting process is analyzed,and the dynamic milling force model is established according to the regenerative chatter model.(2)Based on the commonly used frequency domain and time domain analysis method,This thesis focused on the introduction of the improved full discretization method,which discretizes the time domain factor,the differential factor and the delay factor in the cutting model by the discretization method,thus to achieve the goal of all factors discretization,and tested the method by 1 Degree-of-Freedom(DOF)milling process model,a generally accepted benchmark method,the results show that the method has similar calculation precision and show high efficiency over full discretization method with simple structure.(3)The improved full discretization method is used to calculate the stability prediction of the actual milling process,the different modeling methods for different milling processes are deeply studied.For the 2 Degree-of-Freedom milling,considering the helix angle milling,thin-walled parts milling,the improved full discretization method is used to analyze the stability.In this thesis,the deformation theory of thin-walled parts is combined with the stability theory.For three sides free and fixed thin-walled model,the deformation of thin-walled parts is discussed by Kirchhoff classical plate theory,the finite element ANSYS is used to solve the deformation of thin-walled parts in different machining positions.The complicated deformation of the thin-walled parts in the milling process is obtained,and the cutting deformation and the deformation of the cutting part are obvious and the deformation in the middle part of the workpiece is relatively weak.