Bifurcation analysis for instability detection in high-speed micromilling of thin-walled Ti6Al4V structure

Detection of a low magnitude of chatter in micromilling process is not trivial attributed to non-dominance of the natural frequency; hence, bifurcation analysis has been proposed. Different thin-walled structures have been manufactured by carrying out the low radial immersion micromilling at radial depth of cuts of 30 µm to 130 µm in intervals of 25 µm and at cutting speeds of 20,000 rpm, 50,000 rpm and 80,000 rpm. The micromilling at low cutting speed 20,000 rpm showed circular nature of phase portrait diagram and hence, stability has been achieved. However, Flip (period-2) bifurcation has been detected at 50,000 rpm. Furthermore, increase of cutting speed to 80,000 rpm led to Hopf (Neimark-Sacker) bifurcation. The identified stability and instability based on bifurcation analysis have been used to validate the created stability lobe diagram for micromilling of thin-walled Ti6Al4V workpiece. Machined surface has also been analysed to validate the finding of bifurcation analysis.