Nonlinear dynamic analysis of four-station rotary tool holder subjected to harmonic excitation

Abstract

Four-station rotary tool holder on a lathe is fabricated to achieve transposition operation of turning tools and carry the violent cutting force prior to feed system. Its dynamic characteristic has a potential influence on the structural dynamics and cutting stability of a machine tool. This paper develops a mechanical model for the dynamic characteristic analysis and vibration response prediction. Using the fractal contact theory, the analytical model highlights the rough joint interfacial contact of main components including tool holder body, trapezoidal meshing gear plate and screw shaft. The elastic supports of thrust bearing unit and hollow shaft are also considered. The multi-degree-of-freedom system involving the coupled displacement and piecewise restoring force function is established using lumped mass method. The modal and harmonic excitation tests are performed to investigate the natural property and verify the proposed model. Furthermore, numerical simulation evaluates the effect of external excitation, locking force, fractal parameter, bearing preload and shaft stiffness on dynamic characteristic and stability. The proposed model is promising for the structural optimal design of four-station rotary tool holder.