We have developed a productive-type NC gear grinding machine for automobile plants. A wheel spindle and a workspindle of sufficient rotational speed and torque were newly designed for this machine. An inertial damper provides damping torque to the servomechanism of the workspindle. Since silicon oil as viscous fluid is filled in the inertial damper, the increase of nil temperature decreases the viscosity of viscous fluid and reduces the damping coefficient of the inertial damper. We developed a new type of inertial damper which can withstand the effects of temperature rise. Brushless-servomotors which are built in the wheel spindle and the workspindle are driven with servo-amplifiers. Since the servo-amplifier has a very high power, ripple current in PWM frequency is very large. This ripple current leads to heat generation and induces a strong noise. Therefore, we attempted to decrease the ripple current using a filter. In the experiments, we confirmed that the new type of inertial damper is useful to withstand the effects of temperature rise and the filter is very effective to suppress the generation of heat and noise.
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