Research On Vibration Damping Technology Of CNC Machine Tool Based On Magneto-rheological Fluid

During the process of metal cutting,there are some reasons which lead to the change in relative position between machine tool cutter and workpiece and then form a relatively strong self-excited vibration,that is,chatter.Chatter can affect the quality and precision of parts and the cutting efficiency of machine tool,so the effective suppression of chatter is an important research field in the Machine Tool Industry.Firstly,the phenomenon,mechanism and characteristics of the self-excited vibration are described in this thesis.Then the mechanisms of Frictional Chatter,Coupled Mode Chatter and Regenerative Chatter are studied in perspective of system model and energy transfer.The spindle speed of the turning system and the theoretical formulas of the axial cutting depth are deducted in detail as well as and the relationship graph between them is simulated.In addition,the factors influencing the stability of the chatter are also analyzed.This research demonstrates that the stability of the system can be effectively improved by increasing the stiffness and damping of turning system,which lays a theoretical guidance for the design of the vibration damping device.Secondly,the components,characteristics and relevant working modes of magneto-rheological fluid are briefly described.Then,according to its characteristics,a kind of vibration damping device based on the mixed work of squeezing and shearing is designed.And the design of the vibration damping device in terms of its structure,seal and magnetic path,as well as the selection of the materials are described in detail.Meanwhile,the rules of the magnetic path influenced by different sizes of current,working gap width and materials are analyzed and stimulated.Finally,the dynamic model is reestablished and perfected,and the rules of the frequency response influenced by different stiffness and damping ratio are also analyzed.Finally,the experiments of the vibration are conducted in different contexts by using the designed MR dampers,and the effectiveness of MR dampers on the suppression of the chatter is then examined.Besides,the cutter bar of MR dampers is analyzed in a modal analysis and the natural frequency of the damper in each modal is extracted so as to examine its rationality of the design.