Stability of lateral, torsional and axial vibrations in drilling

Instability caused by whirling, lateral and torsional-axial modes of the drill causes dimensional inaccuracies of the holes and may damage the drills. A generalized stability model for drilling dynamics is presented in this paper. The model considers the regeneration of chip thickness due to the tool deflection in the lateral, torsional and axial directions. The tool wear is considered on damping of high frequency, torsional vibrations during drilling process. The stability for whirling, lateral and torsional axial chatter is predicted simultaneously and analytically in semi-discrete time domain. The stability model is experimentally verified by conducing series of drilling tests with a sharp and worn tool.

► Generalized dynamics of drilling have been modeled. ► The model includes lateral, torsional and axial vibrations. ► Stability of drilling is solved using semi discrete time domain model. ► Sunray pattern is generated by torsional-axial chatter; lobed holes are generated by whirling. ► The dynamics of the drill changes as it enters into the hole due to wall contact.