An Online Active Balancing Method Using Magnetorheological Effect of Magnetic Fluid

The improvement of machining efficiency and precision puts forward new requirements for the balancing performance of machine tool spindle. Work piece quality can be effectively improved by implementing the active balance on the spindle. In this paper, a new active balancing method using magnetorheological (MR) effect of magnetic fluid is proposed. The mechanism of forming compensation mass by changing the distribution of magnetic fluid under local magnetic field is expounded. Experiments are carried out to verify the feasibility of the proposed method. Profile lines of magnetic fluid surface shape at different positions are measured with linear laser projection measurement method in experiments. Three-dimensional (3D) surface shape of the magnetic fluid is reconstructed by the synthesis of the measured profile lines. Experiments demonstrate that mass center of the magnetic fluid increases with the strength of magnetic field. Thus, the feasibility of the proposed method is verified experimentally. In order to weaken the vibration of machine tool spindle using this method, a balancing device is designed, which includes magnetic fluid chambers and three conjugated C-type electromagnets arranged at 120 deg intervals. For each electromagnet, the relationship among compensation mass (the corresponding balancing mass), excitation current, and rotation speed is established. Also, the performance of the balancing device is further proved in experiments conducted on the experimental platform. The imbalance vibration amplitude of the test spindle decreased by an average of 87.9% indicates that the proposed active balancing method in this paper is promising.