Parametric design of boring bars with adaptive tuned mass dampers

Abstract

Slender single point boring tools are damped with tuned mass dampers (TMD) to increase their resistance against chatter. A TMD with fixed parameters may weaken its effectiveness when it is coupled with spindles or bars with different lengths. This paper presents a tunable and parametric, digital design of boring bars. The large length to diameter boring bar is modeled using Timoshenko beam elements and the effects that the TMD head has on the dynamics of the assembled boring bar-TMD system is modeled using a derived analytical expression. A universal TMD head that consists of a carbide mass, oil pocket, and two rubber O rings with experimentally calibrated stiffness and damping as a function of compression is designed. The boring bar has an internal compression shaft that can be pressed against the O ring to vary its stiffness using an integrated power screw. The complete TMD boring bar system is mathematically modeled to determine the Frequency Response Function (FRF) including the required TMD natural frequency and damping ratio to maximize the chatter-free depth of cut. The digital model is verified by comparing the simulated and experimentally measured FRF of the TMD bars. The bars are also tested in boring experiments successfully. • Parametric digital design of boring bars with Tuned Mass Dampers. • Tuning of natural frequency by adjusting O ring compression. • Optimal design of tuned mass damper head with a wide length to diameter ratio (L/D). • Optimal tuning by shrinking the amplitude of the negative real part of the Frequency Response Function (FRF) at the tool locating of boring bar.