Analytical prediction of chatter stability for modulated turning

This paper proposes an analytical chatter stability prediction for low frequency vibration assisted turning process, i.e. the modulated turning. Introducing low frequency tool modulations in machining is initially proposed to transform continuous cutting process into a discrete one so that chip-entanglement/jam could be eliminated. However, tool modulation assistance has a fundamental effect on chatter stability. This paper is the first attempt to uncover the regenerative chatter stability of the modulated turning process by a frequency-domain analysis. Tool engagement kinematics and the dynamic chip generation mechanism are modeled. It is understood that unlike conventional turning or milling processes, modulated turning process exhibits distinct stabilizing effects due to 1) short-time tool engagement and 2) multiple regenerative loops as the dynamic chip thickness is affected by past two revolutions. Considering the average immersion of the cutting tool (cutting duty cycle), a zero-th order frequency domain chatter stability model for the process is proposed. The developed model is used to quantify the effect of multi-delay regeneration and tool modulation parameters on the stability loop formation. The analytical stability solutions are benchmarked against the time domain digital simulation results, and both predictions are validated through orthogonal cutting experiments. It is shown that the proposed solution can accurately generate the Stability Lobe Diagram (SLD) of modulated turning for typical modulation conditions. [Display omitted] •Frequency domain chatter stability analysis in low frequency vibration modulated turning process is firstly proposed.•Relations between tool modulation parameters and the stability are investigated.•Reasons for stabilizing effect by tool modulation are uncovered, and the magnitude of each stabilizing effects are clarified.•Effectiveness of proposed stability analysis is verified through time-domain simulations and cutting experiments.