Numerical investigation of chatter suppression via parametric anti-resonance in a motorized spindle unit during milling

A new concept for increasing process stability during milling processes is presented utilizing a parametric anti-resonance. The beneficial effect is examined by numerical calculations in the time domain for an example spindle which is supported conventionally by ball bearings and is equipped with an additional active magnetic bearing that enables the realization of a deliberate parametric excitation. In the present study the stiffness of this active support bearing is changed periodically with time. The parametric excitation is tuned to a parametric anti-resonance which triggers the transfer of vibration energy between the vibration modes of the underlying system without this additional time-periodicity. It is highlighted how vibration energy is transferred from the first bending mode of the rotor, which is the most critical one by means of regenerative chatter, to a mode with higher damping in order to increase the effective damping of the entire spindle drive unit.