Investigation on surface quality in micro milling of additive manufactured Ti6Al4V titanium alloy

The additive manufactured technology is widely applied to produce titanium alloy parts with complex structures. The subsequent machining operations are necessary for additive manufactured parts to achieve the required machining quality. In this paper, the theoretical surface roughness model in micro milling was established. The model indicated the theoretical milled roughness mainly depends on the feed per tooth, tool nose radius and bottom edge inclination angle. Then, micro milling experiments are conducted on additive manufactured titanium alloy using PCD micro end mill. The surface roughness on milled surface was measured and investigated. At the middle position of micro milled surface, the distribution curves of surface roughness Ra and Sa show the same variation trend under different milling parameters. Moreover, the measured surface roughness results on different transverse positions of milled surface showed that the difference value between the actual and theoretical surface roughness of milled surface is mostly induced by the unstable cutting behaviors, which is also mainly responsible for the surface roughness size effect. The transverse distribution of surface roughness on milled surface exhibited a W shape because of the variation of the instantaneous undeformed chip thickness and material removal mode at different transverse positions.