On cutting process damping for small cutters by including the influences of the dead metal zone and elastic recovery

Abstract

Existing ploughing-based process damping models oriented for the cutting processes did not consider two important factors, i.e. the dead metal zone (DMZ) in front of the rounded cutting edge and the material elastic recovery rate under the clearance face, and thus, they cannot exactly detect the underlying mechanism of process damping in the cutting processes with small cutters. This article systematically investigates the generation mechanism of cutting process damping for small cutters, and proves that the DMZ and the elastic recovery rate have combined contribution to the process damping of small cutters’ cutting. It is theoretically found that in contrast to the full elastic recovery assumed in the macro cutting processes, the material under the cutter’s clearance face is partially recovered in the cutting processes with small cutters, due to the relatively high proportion of plastic deformation. The actual recovery height is numerically calibrated based on the ideal plastic assumption of the stress-strain relationship. Expressions of the statically and dynamically indented areas, which are required for deriving process damping model, are analytically formulated as the functions of the DMZ and the actual recovery height since they greatly change the indentation boundaries between the rounded cutting edge and the clearance face. Above derivations are then utilized to derive the expressions of dynamic cutting forces, and subsequently, the process damping effect is considered to analyze the milling stability. Finally, a series of milling tests with small cutter prove the reasonability of the proposed process damping model.