Research On The Stability Of Thin-walled Parts In High Speed Cutting

With the development of aerospace,the manufacturing level of thin-walled parts has become one of the important signs to measure the national manufacturing capacity and industrial level. In this paper,the research object is based on the milling stability of thin-walled parts,the related problems of the dynamic modeling and simulation of the thin-walled parts are studied. With the frequency response function,the construction of tool-workpiece dynamic model is built. Numerical simulation is carried out with Matlab,and the stability lobe of the thin-walled parts are obtained. High speed, high efficient and high precision machining of thin-walled parts are realized by the optimization of cutting parameters from the chatter diagram. The main issues are as follow:In the thin-walled parts machining, the workpiece deformation has great influence on cutting force. But in the traditional rigid workpiece model, people did not consider that the workpiece elastic deformation would cause the decrease of the cutting thickness, which had resulted in a low prediction accuracy of cutting force. Compared the cutting tool and the workpiece, the workpiece rigidity is weaker, it is necessary to work as the main factors that considering the deformation of the workpiece. By considering the deformation of workpiece, the cutting parameters are modified.Based on the Altintas rigid cutting force model, the flexible workpieces milling force model is established. The milling experiments validates the accuracy of the model, it is of great significance to build thin-walled parts chatter model.The coupling characteristics of cutting tools and workpieces have long been neglected by the academic circles,and a common method of structural dynamic characteristics is analyzed by experimental modal analysis. In the field of engineering vibration commonly used hammer test method, the hammer method is to analyze and process the input and output signals to get the FRF of the system. Then, the fitting curve is obtained by using the admittance curve analysis, and the modal parameters are obtained by parameter identification. The displacement model can be seen that considering tool and workpiece dynamic coupling characteristics of lobes with a higher prediction accuracy. The contact model can be seen the modal parameters of the system depends on the tool, and the workpiece has little influence on the modal parameters of the system, the frequency of displacement coupling is lower than that in the cutting process. Through theoretical analysis, the coupling characteristics of the cutting tool and workpiece have a great influence on the stability of cutting, and the coupling effect is not negligible in the precision prediction of milling stability.Based on Altintas and Budak chatter model, the single degree of freedom chatter model is established. Using the analytic method, the effect of the resonance factor on the stability of the leaf is drawn, and the cutting parameters are optimized. Using the time domain numerical method, the effect of the variable milling force coefficient on the stability of the chatter lobe is considered. The results show that the critical axial depth is increased as the decrease of the radial depth of cut, and the shape of the chatter lobe is also changed obviously. By taking the factors of cutting tool and workpiece into account, the relative transfer function is obtained, and the four degree of freedom model is set up. The accuracy of the model is proved by comparing the stability of the tool or the workpiece.