A noise-free servo-spindle for high-speed NC gear grinding machines

The authors developed a productive type NC (numerically controlled) gear grinding machine for automobile plants. This NC machine requites high-accuracy synchronization between the grinding spindle and workspindle. We must use high-power servomotors and servo-amplifiers to satisfy the specification required for high-speed grinding. However, since the high power servo-amplifier causes very large ripple of motor current at PWM (pulsewidth modulation) frequency and induces strong noise, it becomes difficult to get the stable synchronous rotation among spindles. Therefore, the authors tried to use two-phase type PLL to achieve noise-free high-speed synchronous spindles and to reduce the noise caused by the current ripple with a kind of current filter. In this paper, an approach for suppressing the noise and experimental results are described