Generalized modeling of milling dynamics for the 4DOF machining system with asymmetric flexibility

Abstract

Asymmetric flexibility of the machining system exists widely in the practical milling process. In this paper, a generalized milling dynamics modeling method for an asymmetric flexible 4DOF cutter-workpiece system is proposed, which is further used to reveal how the asymmetric flexibility affects the milling dynamics characteristics. The regenerative milling force model is firstly established through the coupling coefficient matrix, in which the milling condition with non-parallel direction between the axis directions of coordinate system, the vibration directions of system DOF and the acting directions of milling force are well handled. Then, a generalized 4DOF milling dynamics model considering a new dimension, namely the cutter and workpiece feed direction angle combination ψ (ψc, ψw), is presented. The studies point out that the milling dynamics characteristics of the asymmetric flexible machining system, including the milling stability and surface location error (SLE), have a significant feed direction-dependent feature. Moreover, the generation mechanism of this kind of asymmetric milling dynamics has been successfully clarified. The proposed method has been experimentally validated by a series of milling tests in an asymmetric flexible machining system. Lastly, the influences of the asymmetry degree of the system flexibility, milling type and radial depth of cut on the milling dynamics are both analyzed by numerical simulation.