On the influence of drilling depth dependent modal damping on chatter vibration in BTA deep hole drilling

BTA (Boring and Trepanning Association) deep hole drilling is applied for machining bore holes with a high length to diameter ratio. The slender tools involved make BTA processes highly susceptible to chatter vibration. Chatter-free states and states with chatter vibration corresponding to one of the first three torsional eigenfrequencies can be observed to alternate during processes with constant cutting parameters. A detailed FEA model of the significant BTA tool components involved was developed. This takes into account the drilling depth variant boundary conditions. Using this model, the state transitions can be attributed to drilling depth dependent modal damping of the involved torsional vibration modes.