Keiichi Nakamoto, Shinya Mitsuhashi, Kazuhiko Adachi, and Keiichi Shirase

Abstract:
A machine tool spindle is a key component affecting the performance of machine tools. Spindle vibration of machine tools causes tool wear prematurely and decreases machining accuracy. The vibration changes depending on the used tooling and the rotation speed during various machining operations. In particular, even small unbalance mass of the spindle makes large whirl in high speed machining. However, real-time balancing of a machine tool spindle has not yet been realized successfully including the influence of the used tooling. In this study, in order to reduce unbalance response of a machine tool spindle and to achieve high accuracy machining, a real-time balancing mechanism using magnetic fluid is proposed. The magnetic fluid is enclosed inside the spindle, and the distribution of circumferential mass is controlled to compensate for unbalance mass in real-time. A test spindle is designed and developed in order to evaluate the real-time balancing mechanism experimentally. It is confirmed that unbalance response of the spindle is significantly improved. Based on the obtained results, a machine tool spindle achieving real-time balancing is developed in this paper. The experimental results proved the feasibility of the proposed real-time balancing mechanism for a machine tool spindle.

Keywords: machine tool spindle, real-time balancing, magnetic fluid, smart spindle, vibration control, unbalance mass