Analysis And Research On Cutting Stability And Dimensional Accuracy Of Slender Shaft Machining

Aviation slender shaft is one of the important parts in aeroengine.It is mainly used to transmit transmission torque and support transmission parts.Its length diameter ratio is usually more than 20,and its rigidity is very poor.Machining deformation and cutting chatter are very easy to occur during its turning process,resulting in a low machining efficiency and difficult to ensure the dimensional accuracy of parts.In order to meet the increasing requirements of the national economy and national defense industry for the manufacturing accuracy of key parts of aeroengine,this paper intends to explore the machining deformation and cutting chatter mechanism of slender shaft of aviation difficult machining materials through comprehensive means such as mathematical modeling,finite element analysis and cutting test,and analyze the influence of process conditions and cutting parameters on machining deformation and cutting stability.It explores a feasible way for the high-efficiency and precision machining of such parts.The main research contents of this paper are as follows:Firstly,the vibration of slender shaft turning is modeled and solved,the vibration response equation of slender shaft when the cutting force acts on different positions is obtained,and the external contour of slender shaft turning is predicted.Then,according to the definition of cylindricity,the evaluation of slender shaft cylindricity after turning is realized,and the influence of cutting conditions such as feed rate,cutting depth,tool rake angle and tool tip arc radius on cylindricity is analyzed.Secondly,through the finite element analysis software ANSYS,the machining deformation of slender shaft workpiece is predicted,and the machining deformation of slender shaft workpiece with different length diameter ratio is studied with the assistance of the follow tool rest with different stiffness.The modal analysis and harmonic response analysis of the workpiece system are carried out,and the changes of the natural frequency and peak variation of harmonic response at the cutting point of the workpiece system before and after the use of the follow tool rest are compared.The results show that the use of the follow tool rest can significantly improve the natural frequency and reduce the peak variation of harmonic response,which theoretically proves the effectiveness of the follow tool rest in restraining the turning vibration deformation of slender shaft workpiece.Finally,the weakly rigid workpiece system for turning slender shaft is simplified into a clamped-pinned beam structure,and the frequency response function of the cutting point position is obtained according to the bending vibration theory of the beam.On this basis,the modal parameters of the workpiece system are obtained by orthogonal polynomial modal parameter fitting.By coupling with the modal parameters of the follow tool rest,the frequency response function of the cutting point position of the workpiece system with follower is obtained.By establishing the turning dynamic equation considering regenerative effect,the prediction of turning stability lobe diagram of slender shaft is realized.The corresponding simulation program is developed by MATLAB,the experimental verification and correlation analysis are carried out,and some guiding conclusions are obtained for the realization of chatter free machining of slender shaft.