Micromachining of coarse-grained aluminum including crystallographic effects

Abstract

This paper presents an experimental analysis of the effects of crystallographic anisotropy of the workpiece material when machining coarse-grained pure aluminum under varying cutting conditions. Orthogonal cutting experiments were conducted on an instrumented planning setup, and cutting forces and surface roughnesses were measured in a full-factorial experimental design. Cutting speed, uncut chip thickness (feed), and tool rake angle were varied at multiple levels. To determine the effect of subsurface deformation left by the previous tool passes, experiments were conducted both with and without cleanup cuts that reduce the surface deformation. The effect of crystallographic orientations and their interaction with cutting conditions on the specific cutting energy, the effective coefficient of friction, and the resulting surface roughness were analyzed through an analysis of variance approach. It was concluded that the crystallographic anisotropy has a strong effect in specific cutting energies, with up to 360% variation across different grains. Similarly, the roughness of the machined surface was seen to vary significantly (up to 831%) with the crystallographic orientations. On the other hand, the effective coefficient of friction was observed to be insensitive to the changes in crystallographic orientations. Lastly, a significant (up to 45%) difference in specific cutting energies was observed between the cases with and without cleanup cuts, indicating the strong presence and the influence of sub-surface deformation.