Fig.5 Powder flow rate vs porosity  
In LENS, powder feed rate is crucial as well. If the feed rate is reduced, there could not be enough powder to fill the space between two parallel lines, leading to porous zones. On the other hand, a thicker layer produced by a high feed rate may damage the integrity of the following build layers or result in part non-uniformities. The height of the deposited bead is mostly influenced by the powder flow rate. This is due to the fact that more material is capable of entering the melt pool and forming beads. The width of the bead can also be influenced by the powder flow rate, but this often only happens when the extra bead width is fused to the rest of the deposited material and not the substrate itself. It can be seen in Fig. 4 that for a constant laser power of 250W, lowering the powder flow rate results in a 0.8% decrease in sample porosity .