Regenerative and frictional chatter in plunge grinding

This paper studies self-excited vibrations, regenerative and frictional chatters, in a plunge grinding process. In consideration of lateral and torsional workpiece movements, a dynamic model with four degrees of freedom is proposed, which involves state-dependent time delays and Stribeck effect for regenerative and frictional effects, respectively. With this model, by linearising contact angle, regenerative grinding depth, frictional velocity and the state-dependent delays, eigenvalue analysis yields stability diagrams for the grinding, where boundaries for both regenerative and frictional instabilities are determined. Then, near the boundaries, simulations and bifurcation analyses are performed to reveal patterns of chatter onset. Bifurcation diagrams show coexistence of stable grinding and the regenerative chatter near the regenerative boundary, and a sudden switch between the stable and the frictionally unstable on the frictional boundary. Moreover, simulation results also show various dynamical properties in the grinding chatters, such as effect of losing contact and stick-slip motion.