| In recent years,with the rapid development of China’s basic processing and manufacturing industry,aerospace and automotive manufacturing and other fields for workpiece processing accuracy requirements are more and more high,especially for the complex structure of the key parts and thin-walled cavity parts is the need for large aspect ratio milling cutter processing.Due to the lack of dynamic stiffness of large aspect ratio tool bar,chatter is easy to occur in the process of machining,which seriously affects the machining accuracy and tool service life.Aiming at the problem of vibration reduction of large aspect ratio cutters,domestic and foreign experts and scholars have studied active control,passive control and semi-active control and other related vibration reduction technologies.Passive control vibration reduction technology has been widely used because of its simple structure,convenient disassembly and high stability.The rubber elastic components of the dynamic damper in the traditional passive damping cutter bar are prone to fatigue aging.The viscosity of the damping liquid is greatly affected by temperature.The insufficient sealing of the cutter bar often leads to the leakage of the damping liquid,which destroys the design stiffness value and damping value,and reduces the damping effect and service life of the dynamic damping cutter bar.To solve the above problems,a new type of permanent magnet dynamic damping milling cutter was designed based on magnetic stiffness and eddy current damping,which realized the independent and accurate design of stiffness and damping.The theoretical calculation models of magnetic force and eddy current damping force in permanent magnet dynamic shock absorber were established by using equivalent magnetic charge method and Biot-Safar law respectively.MATLAB and Maxwell software were used to carry out numerical simulation and finite element simulation analysis of magnetic force and eddy current damping force in permanent magnet dynamic shock absorber,and the influence of structural parameters of each part on magnetic stiffness and eddy current damping was explored.Considering the traditional design method of large length-diameter ratio vibration damper cutter,the design method of permanent magnet dynamic vibration damper cutter was proposed,and the relevant dynamic parameters of single-stage stacked permanent magnet dynamic vibration damper cutter and multiple permanent magnet dynamic vibration damper cutter were optimized.Firstly,the parameters of the single-stage stacked permanent magnet dynamic vibration absorber were optimized with the PQ fixed-point theory,and the optimal magnetic stiffness and eddy current damping parameters of the permanent magnet dynamic shock absorber were determined,and the vibration damping effect of the permanent magnet dynamic vibration absorber was verified by comparing the amplitude variation of the frequency response function of the main system of the cutter bar.A simplified dynamic model of the multi-permanent magnet dynamic damping milling cutter was established,and the amplitude expression of the frequency response function of the main system was obtained.The maximum amplitude of the frequency response function of the main system was taken as the optimization objective,and the parameters of the multi-dynamic shock absorber were optimized by using particle swarm optimization algorithm.respectively determine the 1,2 and 3heavy permanent magnet,the optimal vibration parameters of dynamic vibration absorber,And the amplitude contrast curve of frequency response function was plotted.Finally,ANSYS finite element software was used to carry out the finite element modal analysis and harmonious response analysis of ordinary tool bar,single stage permanent magnet dynamic vibration damping tool bar and multiple permanent magnet dynamic vibration damping tool bar.The amplitude variation of frequency response function of three tool bars was compared,and the vibration damping effect of permanent magnet dynamic vibration damping tool bar was verified.The cutting stability diagrams of ordinary solid tool bars,single-stage stacked permanent magnet dynamic vibration damper bars and multiple permanent magnet dynamic vibration damper bars were drawn by MALAB simulation,and the vibration reduction effect of permanent magnet dynamic vibration damper bars was verified by comparing the stable limit cutting depth. |
