A simulation study of local powder bed gas shielding in Selective Laser Sintering / Melting machines

Abstract

In Selective Laser Sintering and Melting it is necessary to protect metal powder deposited on the powder bed from contact with atmospheric air, which may lead to oxidation and downgrading of the properties of the powder in the presence of high temperature that is necessary for achieving full or partial melting. Thus, the building chamber of commercially available SLS/SLM machines is fully isolated and filled with inert shielding gas which may need to be replenished before each build session thereby raising both machine building and consumables costs. In this paper, it is examined using Computational Fluid Dynamics how protection of the powder area around the laser spot can be achieved by locally insulating it from air by gas circulation in a suitably designed box moving with the laser beam. Full coverage of the respective area and at the same time no disturbance of the powder particles within it are critical requirements. Two concept variants are studied and simulated with promising results.