Track geometry variations in selective laser melting processes

Selective laser melting processes are widely used for many industrial applications using a laser beam to melt preplaced powder material layer by layer to create technical parts. The building process of those structures requires remelting of adjacent tracks and layers in order to avoid cavities and achieve the joining of the new track to the previous track and layer. In order to achieve a sufficient overlap and minimize cavities, usually conservative processing parameters are chosen. A higher energy and powder usage efficiency would be achieved if knowing about the formation process of the single tracks and their geometrical dimensions depending on the available powder. In this work, it is shown that the cross-sectional track geometry significantly varies within one layer. A simple model is developed describing the influence of the available powder for each track within one layer. Depending on the hatch distance, different variation patterns are observed and modeled showing that the track variations are inherent phenomena of the process. It can be concluded that the variations of powder availability can cause the geometric variations of the tracks.