Realization of Real-Time Balancing of a Machine Tool Spindle Using Magnetic Fluid
Keiichi Nakamoto*, Hidenori Nakatsuji**, Shinya Mitsuhashi***,
and Keiichi Shirase**
*Department of Mechanical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
**Department of Mechanical Engineering, Kobe University, 1-1 Rokko-dai, Nada, Kobe 657-8501, Japan
***Mitsubishi Heavy Industries, Ltd.
Tool vibration shortens tool life and lowers the quality of the machined surface. Even a small mass imbalance in the spindle and tooling generates tool vibration. Additionally, in machining operations, different tooling setups including the cutting tools rotate at different speeds for each machining operation, making it difficult to reduce tool vibration. In order to solve the problem, real-time balancing using magnetic fluid was proposed in our previous study. Magnetic fluid is a type of smart fluid comprised of a stable colloidal suspension of magnetic nanoparticles in a liquid carrier, and its viscosity and behavior are precisely controlled by changes in magnetic field intensity. To compensate for the mass imbalance of a spindle and tooling in real-time, the magnetic fluid enclosed inside the spindle is controlled to alter the distribution of circumferential mass by adjustments in the intensity of the magnetic field made from outside the spindle. Thus, tool vibration, which changes frequently depending on tooling during various machining operations, can be reduced successfully. In this paper, a machine tool spindle with the proposed real-time balancing is developed, and several experiments are conducted. It is confirmed that the mass imbalance in the entire rotating system is significantly reduced in real-time, and tool vibration is effectively suppressed as well.
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