Turning Dynamics: Part 2 — Stability at High Speed
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A comprehensive 3D lathe cutting model is validated by comparing numerical simulations to the experimental data obtained in Part 1 using instantaneous frequency. Comparison of chatter-free cutting demonstrates that the model effectively captures the work-piece natural frequency, tool natural frequency, a nonlinear mode, and the spindle speed, which are main components of the underlying dynamics observed experimentally. The model accurately simulates chatter vibrations characterized as increased vibration amplitude and the appearance of coupled tool - work-piece vibrations at a chatter frequency. The stability diagram constructed by running the model at various spindle speeds and depth-of-cuts demonstrates a general increase in the chatter-free critical depth-of-cut as the spindle speed increased. This chatter-free limit begins to exponentially level out as the spindle speed exceeds 1500RPM. At high spindle speeds the work-piece motions dominate the cutting dynamics, resulting in cases of excessive work-piece vibration amplitude and highly nonlinear frequencies which affect the efficiency of the process. The excessive work-piece amplitude cases create a second stability limit to be considered as a result of imbalance and configuration of the work-piece. Thus, workpiece dynamics should not be neglected in mathematical and experimental analyses for the design of machine tools and robust cutting control law. Copyright © 2012 by ASME.
author list (cited authors)
Halfmann, E. B., Suh, C. S., & Hung, N. P.