Methodologies for characterization of smearing micro geometry on ball end milled tool steel surfaces

Manufacturing surfaces with nanoscale roughness by machining involves several material removal steps among which a final shallow cut to reduce the scallops height produced by the cutting tool geometry. When the cutting tool engages the workpiece with small depth of cuts, the thickness of the chip becomes comparable to the cutting edge radius. In this configuration, the material is not completely removed but it is deformed and smeared onto the surface, increasing the surface roughness. In this work two different methodologies are proposed in order to quantify the volume of the chip that is subjected to smearing phenomena. Measurements of volumes at such scale length are not straightforward, therefore a combination of confocal and electron microscopy techniques are used in a synergistic way to increase the robustness of the methodologies. The results will help in further understanding and modelling the occurring of the smearing phenomena in milling for finishing operations.