Powder Bed Fusion (PBF) technologies

The following table lists the PBF technologies, classified according to the type of materials they process and the fusion heat source.

The production process of each AM technology consists of a sequence of cycles for production of individual horizontal layers of products. With PBF technologies, each of the layers is manufactured by joining particles of a thin layer of a powder. The production cycle of a PBF technology starts with addition of a small amount of the production powder mixture to the production chamber (top left image in the figure above). The image shows that the addition is achieved by rising of the movable bottom of the powder container, but other solutions exist as well. Using a recoater with horizontal motion, the added production powder is then distributed uniformly over the surface of the production chamber (top right image in the figure above), thus forming a thin layer of the production powder that covers the area where the products are built, which is called the powder bed. The areas of powder bed that belong to cross-sections of the products are then exposed to selective action of an intensive, but short, heat pulse that causes melting of the powder. After the heating stops, the melted material rapidly cools and solidifies (bottom left image in the figure above) into a new layer that joins to the previously manufactured layers of the products. After the manufacturing of a layer of products, the bottom of the production bin, which contains the products and the powder which was not exposed to the selective action during the process, is lowered, so that the top of the production bin may be covered by the powder added for manufacturing of the next layer of products in the following production cycle.

The described principle of operation causes some common properties of product of all PBF technologies:

• high mechanical properties, the strength of products is comparable to products of traditional technologies;
• small anisotropy, in general smaller than with majority of AM technologies; the anisotropy may be minimized by proper application of DfAM rules and post-processing by heat treatment;
• sensitivity to residual stresses, which arise as a consequence of high temperature gradients due to fast heating and cooling; as the anisotropy, the internal stresses may be reduces by proper application of DfAM rules and post-processing;