Regenerative chatter in a plunge grinding process with workpiece imbalance

Grinding vibrations caused by regenerative cutting force and workpiece imbalance are discussed in this study. To regenerate workpiece surface, a grinding wheel is rotated, and pushed towards a rotating workpiece, rubbing and cutting its surface, with regenerative and frictional interactive forces generated. Besides, any mass imbalances of the rotating workpiece or the wheel is another source of vibration. To investigate both effects of the regeneration and the mass eccentricity on the grinding dynamics, a mathematical model with time delays and sinusoid excitation has been developed and analysed. By calculating eigenvalues with continuation scheme, linearly grinding stability is obtained and presented in a lobes diagram, where chatter-free and chatter regions are identified. For chatter without workpiece imbalance, a classical periodic chatter induced by the regenerative effect is found. With imbalance, forced periodic vibration, chatter quenching, quasi-periodic chatter and periodic chatter are obtained in different regions.