Authors: Yuto Horigome, Fumihito Sakurai, Shinichi Nishida.
Since the overhang of the boring bar is large in the boring process using the NC lathe, the vibration of the boring bar is often a problem. It is necessary to reduce the tool vibration because surface roughness and tool life are greatly affected by the tool vibration. In this study, the application of damping alloy for the NC lathe sleeve was proposed. The characteristic of damping alloy is absorb vibration by transforming dynamic energy of the vibration into heat energy. A cutting experiment was operated by using the new type sleeve made of only damping alloy and the traditional type sleeve made of steel. The results such as vibration, surface roughness and tool life are compared between the both tools. The tool vibration became small and the tool life became long with new type sleeve compared to the traditional type sleeve. However the surface roughness became large by using new type sleeve. It is supposed that the rigid of new type sleeve is smaller than that of traditional type sleeve.
Therefore, the composite sleeve that was combined with damping alloy and steel was developed for improving the rigidity. As a result, the tool vibration using the composite sleeve indicated one fifth and the surface roughness became half compared to the steel sleeve. The vibration analysis based on this experimental results was studied to clarify the vibration mechanism. The modal analysis was operated with the structural analysis software by using 3D models. And the FFT analysis was operated by the vibration data. As a result, it was revealed that the natural frequency of cutting tool system with new type sleeve was changed compared to the traditional system. And it was revealed that the bending mode frequency was closed to the twist mode frequency.
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