Chatter in interrupted turning with geometrical defects: an industrial case study

In this paper, machine tool chatter arising in an interrupted turning process is investigated in a strong industrial context with a complex flexible part. A detailed analysis of the real cutting process is performed with special respect to the geometrical defects of the part in order to highlight the source of machine tool vibrations. The analysis is completed by simple models to estimate the forced vibrations in interrupted turning, the gyroscopic effect, and the mode coupling using a new simplified formulation. Then, a new dynamical model with interrupted cutting and geometrical inaccuracies-runout and orientation of eccentricity-is presented. Stability analysis of this model is performed by the semi-discretization method, an improved technique for analyzing delay-differential equations. The use of all these models on a given machining configuration allows comparing several vibration mechanisms. Thus, behavior's specificities are highlighted, especially the influence of eccentricity runout on stability. A sensitivity analysis shows the effect of the value and the orientation of the geometrical defects for low speed conditions. Then this result are extrapolated to high-speed conditions to look for possible new stable cutting conditions and shows a period doubling flip instability, never described before in turning operations. The main focus of this paper is developing and exploring a stability model for interrupted cutting in turning with geometrical defects. The complexity of the industrial context led to methodically compare different chatter and vibration mechanisms; this approach can be generalized to other industrial contexts.