Prediction of the dynamic stiffness of boring bars

The productivity of boring operations is limited by chatter vibrations, as an effect of the low dynamic stiffness and damping of these cantilevered structures. The origin of the beforementioned self-excited vibration is mainly related to the dynamic stiffness of the boring bar’s bending mode, which is influenced by the stiffness and damping of the machine tool interface. In this paper a dynamic model is presented, which uses Timoshenko beam theory for the boring bar itself, while the effect of the clamping is experimentally determined applying Receptance Coupling Substructure Analysis (RCSA). The important effect of the boring head at the tool tip is considered on the coupling as well. This way, once the machine interface is characterized, the Frequency Response Functions (FRF) of different boring bars can be predicted.