MODELING MACHINING DYNAMICS INCLUDING DAMPING IN THE TOOL-WORKPIECE INTERFACE

Machining instability, namely chatter, occurs due to the interaction b etween the structural dynamics and the cutting process. The process da mping generated at the tool-workpiece interface is an important parame ter of that interaction. A significant enhancement to the chatter simu lation model in milling is presented. It includes tracking of the inte rference between the tool flank and the generated wavy surface, which is the source of process damping. Results of simulation runs performed to determine the limits of stability are presented for sharp tools as well as for tools with various amount of flank wear. The phase relati onship between the ploughing force and tool vibrations is explained us ing these simulations. It is also shown that the improved model accura tely predicts the increase in the limit of stability due to tool wear, as well as the effect of the wave length of the machined surface undu lations on process damping. Cutting tests of aluminum confirmed the si mulation results.