Enhancing productivity in Laser Powder Bed Fusion (PBF-LB/M) via layerwise Laser Remelting – proof of concept

Abstract

Abstract A limiting factor for a widespread application of laser powder bed fusion (PBF-LB/M) is
the necessary compromise between quality and productivity resulting in high manufacturing
costs. The productivity can be enhanced by increasing the layer height. However, this adjustment
may result in either insufficient bonding due to inadequate laser energy input for complete melting
or in an increased surface roughness and porosity through excessive energy density. The
increased energy input required for complete melting of a high layer height induces the Marangoni
effect which promotes an increase in surface roughness of the interlayer. Interlayer roughness
peaks act as undercuts regarding the recoating process and result in local low density of the
powder bed and thus porosity. Therefore, the requirements for a laser exposure are an adequate
melt pool depth and a sufficient interlayer surface quality. For high layer heights and thus high
productivity it is not possible to meet both requirements with a state of the art exposure strategy.
This work studied the feasibility of using layerwise laser remelting to smooth out roughness peaks
after the first laser exposure with high energy density when using high layer height. A positive
impact of the laser remelting on penetration depth and porosity was observed. Copper samples
printed using the remelting strategy and a layer height of 60 µm achieved comparable values of
porosity as samples with a layer height of 30 µm and a state of the art melting strategy. This
approach resulted in time savings of 28 % while maintaining high part quality.