Influence of Powder Distribution on Process Stability in Laser Beam Melting: Analysis of Melt Pool Dynamics by Numerical Simulations
The occurrence of defects in the additive manufacturing process of laser beam melting in metal powder bed can be reduced through empiric parameter optimization – but knowledge about basic effects like the influence of the composition of the powder layer on the melt pool is still limited. Particle size distribution and powder layer inhomogeneity after layer coating influence melt pool dynamics and may cause defects in the work pieces. This correlation can hardly be analyzed in experiments, so a three-dimensional transient numerical simulation model is used. The model is based on the continuity equation, the heat equation and the Navier-Stokes equation. Therefore, the finite-volume method capabilities in OpenFOAM are used. The free surfaces of the multi-phase system are calculated using the volume of fluid method. The powder beds have unimodal or bimodal distributions without random effects in the particle composition. Their density and thermal conductivity is adapted to reality. The investigations of the melt pool and the porosity formation demonstrate an advantage of more and smaller particles in the powder for compensation of defects in the powder bed, similar to the results of the experiments.