Mechanistic Modeling of Process Damping in Peripheral Milling

Abstract

This paper extends analytical modeling of the milling process to include process damping effects. Two cutting mechanisms (shearing and plowing mechanisms) and two process damping effects (directional and magnitude effects) are included. The directional effect is related to vibration energy dissipation due to directional variation of cutter/workpiece relative motion. The magnitude effect is associated with change in force magnitude due to variation of rake angle and clearance angle. Process damping is summarized as containing these separate components; direction-shearing, direction-plowing, magnitude-shearing and magnitude-plowing. The total force model including the process damping effect is obtained through convolution integration of the local forces. The analytical nature of this model makes it possible to determine unknown process damping coefficients from measured vibration signal during milling. The effects of cutting conditions (cutting speed, feed, axial and radial depths of cut) on process damping are systematically examined. It is shown that total process damping increases with increasing feed, axial and radial depths of cut, but decreases with increasing cutting velocity. Predictions based on the analytical model are verified by experiment. Results show that plowing mechanism contributes more to the total damping effect than the shearing mechanism, and magnitude-plowing effect has by far the greatest influence on total damping.