Eddy-Current Actuated the On-Machine Spindle Balacing Device

• Main Authors: Kung-ying Li, 李坤穎
• Other Authors: Zheng-Xiong Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/55532701531354542609

碩士 === 國立中正大學 === 機械工程所 === 95 === The machine tool technology trend is toward the higher cutting speed at the same time higher precision. For the machining center, there are one-side tolerances designed respectively on the matching taper surfaces of the spindle nose and tool holder. The one-side tolerances are required due to the automatic tool change requirement. However, the one-side tolerance also creates a mass-unbalancing problem every time after a tool change operation. Because this unbalance problem is created after the spindle and tool engaged, therefore, the traditional off-machine method is not applicable to this problem. We must rely on an on-machine balancing technique which balancing the engaged tool and spindle in a whole unit. In this work, we develop an on-machine balancing technique based on the eddy current actuator principle. There are two known counter-weight balancer rings mounted on the spindle. Current pulses are applied to the balancing system to generate a pulsed force which is in the tangential direction of the balancer ring. Every pulsed force will push the ring moving a small angular step. The advantages of our approach include non-contact, small size and low cost. Experimental results have proved that 0.1o angular step has been achieved using pulsed 3A current in a pulse rate of 100 Hz when the spindle speed is 5000 rpm. The higher spindle speed will generate higher actuating force. Therefore, another advantage of this method is higher actuating efficiency in higher spindle speed. We also developed an analog phase detection circuit which is designed to replace the time-consuming FFT (Fast Fourier Transform) process. Therefore, the cycle update rate of the balancing method can be increased. A correlation coefficient method is implemented to identify the magnitude and phase of the unbalanced mass of the spindle. The identified unbalance mass is then compensated by the proposed method. The experimental result demonstrated that the spindle vibration has been cut down 90% after balancing. Key words: machining center, spindle balancing, on-machine balancing, eddy-current actuation