Machine tool motorized spindle usually encounters mass imbalance in the operational process. In order to enhance the machining efficiency and precision, on-line active unbalance compensation technique is becoming the first choice of vibration suppression for machine tool spindle. This paper proposes a new motorized spindle integrated with one electromagnetic ring balancer. Firstly, the three-dimension structural design of the integrated spindle is described in detail. Then, the balancing principle of electromagnetic ring balancer is set forth. In order to disclose the structural characteristic and determine the reasonable square wave drive parameters, the finite element calculations are carried out to obtain the relationship between the torque and rotational angle of counterweight disk when coil is not electrified, and the movement curve when coil is applied different currents. Based on the steady-state and transient electromagnetic field simulations, a specific spindle prototype with one electromagnetic ring balancer is developed. For the prototype, vibration test rig is built to verify the balancer design correctness, fabrication quality and vibration reduction effectiveness. The experimental results show that the proposed balancer has a smooth movement process under square wave drive, a desired unbalance response and the spindle vibration can be effectively reduced in a semiautomatic balance way, which is very beneficial to the improvement of operational precision and service life of machine tool motorized spindle.
Enhancement-mode AlGaN/GaN HEMTs with high linearity fabricated by hydrogen plasma treatment
