Optimally tuning an absorber for a chatter-resistant rotating slender milling tool holder

Abstract

Machining of parts with deep pockets necessitates the use of long slender milling tooling systems with absorbers integrated within them to make the milling process chatter vibration resistant. As milling tools rotate, their dynamics change with speed. Hence, the use of classical analytical methods of tuning absorbers that presume the primary system to have fixed parameters may result in suboptimal designs. To address this, we present methods to tune an absorber integrated within a rotating milling tool holder while accounting for its speed-dependent characteristics. The milling tool holder is modelled as a rotating cantilevered Euler-Bernoulli beam with small distributed viscous damping and a secondary absorber system attached at a point along its length. The governing equations of motion account for all the artifacts associated with rotation viz. gyroscopic, Coriolis, and the centrifugal effects. Rotational effects couple vibrations in orthogonal planes and make the cross frequency response functions as flexible as the direct ones. Since these speed-dependent dynamic characteristics govern the chatter-free machining stability limits, maximization of this limit is treated as the objective function to find the optimal mass, stiffness, and damping of the absorber. We find that an optimally tuned absorber using the proposed approach results in a∼16.5 fold improvement in the chatter-free machining capability as compared to a∼11.5 fold improvement using other classical methods of tuning the absorber.