Analytical prediction of chatter stability in turning of low-stiffness pure iron parts by nosed tool

Abstract

Regenerative chatter is a pivotal obstacle for achieving required machining quality and efficiency in turning operations, especially when turning of low-stiffness parts. Accurate prediction of chatter stability prior to actual machining is of great significance for the judgment on feasibility and the optimization selection of cutting parameters that are free of chatter. To this end, this paper presents a comprehensive study which allows accurately predicting the chatter stability in turning of low-stiffness parts made of pure iron. The dynamic model for a double-flexible turning system with the regenerative effect is established in orthogonal directions on the basis of a nonlinear turning force model with accurately calibrated nonlinear force coefficients. In the nonlinear turning force model, both shearing and edge effects are considered, in which shearing force components are formulated as the exponential functions of the instantaneous uncut chip thickness to reflect the size effect. In addition, the geometric feature of the tool nose radius is also taken into account by precisely discretizing the instantaneous uncut chip area. The chatter stability of the resulting system is further predicted by an extended second-order semi-discretization method (2nd SDM). To verify the proposed method, a series of cutting tests are conducted on a CNC lathe, and experimental results indicate that proposed method can achieve an accurate prediction of chatter stability in turning of low-stiffness pure iron parts.