Modeling the Dynamic Properties of Conventional and High-Damping Boring Bars

Nowadays, the availability of reliable mathematical models of machining system dynamics is a key issue for achieving high quality standards in precision machining. Dynamic models can indeed be applied for tooling system design, preventive evaluation of cutting process stability and optimization of cutting parameters. This is of particular concern in internal turning, where the cutting process is greatly affected by the compliance of the tooling system. In this paper, an innovative hybrid dynamic model of the tooling system in internal turning, based on FE beams and empirical models, is presented. The model was based on physical and geometrical assumptions and it was refined by using experimental observations derived from modal testing of boring bars with different geometries and made of different materials, i.e. alloy steel and high-damping carbide. The predicted modal parameters of the tooling system (tool tip static compliance, natural frequency and damping coefficient of the dominant mode) are in good accordance with experimental values.