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Machining chatter in continuous facing under a constant nominal cutting speed: Tool vibration with time-varying delay

This article studies regenerative chatter in single-point face-machining at nominally constant speed under continuous conditions. A temporal model for rotational speed was developed and experimentally verified. The resulting rotational time-delay was cast into the classical force feedback mechanism for chatter. A chatter model was formulated to allow slight spindle speed variation about the temporal model. The modified method of steps was then employed to solve the tool vibration in time-domain allowing one (single-degree-of-freedom) or two (2-degree-of-freedom model) vibrational modes. Exploratory facing experiments using a grooving tool were conducted on a nickel alloy workpiece. It was found that the tool was more susceptible to chatter at larger diameters. It appeared that the single-degree-of-freedom model captured the most relevant of the observed phenomena while cutting without spindle speed variation, however, neither the 1-degree-of-freedom nor the 2-degree-of-freedom models could effectively capture the experimentally observed chatter evolution characteristics while cutting with spindle speed variation.