Thin-Walled Part Properties in Powder Bed Fusion of Polymers—A Comparative Study on Temperature Development and Part Performance Depending on Part Thickness and Orientation

Abstract

To develop new areas of application for laser-based powder bed fusion of polymers (PBF-LB/P), a deeper process understanding of the resulting mechanical properties, particularly for thin-walled and complex structures, is needed. This work addresses the influence of part thickness and orientation in detail. For a general understanding, two PBF systems were used. For comparison, the normalized energy density was determined for specimens of various thicknesses and orientations. It could be seen that the normalized energy density exhibited opposing trends for the two systems for progressively thinner samples. During the process, the exposure temperature development was observed using an infrared camera for a greater understanding of the developing part properties. To further investigate the fracture behavior, an infrared camera was used during tensile testing, which revealed various patterns depending on the PBF-System used. The results showed a machine-dependent difference in the exposure temperatures and elongation at break for z-oriented parts. While the surface roughness was independent of the thickness, the density, porosity, and the mechanical properties were affected significantly by the part thickness. The parts showed a brittle breaking behavior with a crack initiation from the short side of the tensile bar. These results improved process expertise, and in particular the mechanical performance of thin-walled structures caused by temperature variations in PBF-LB/P.

Laser-Sintering of Cyclic Olefine Copolymer for Low Dielectric Loss Applications

“…However, these properties were not sufficient for a reliable and uniform recoating process, a hypothesis that was confirmed during coating tests. In contrast, PA2200 demonstrated a compression depth of about 95 µm and a specific bulk density of 0.45 g/cm 3 [ 32 ], with preliminary studies indicating that materials with compression depths lower than 200 µm are generally more suitable for processing. To improve the flow characteristics of the COC powder, the study experimented with adding aluminum oxide type AluC and fumed silica type Aerosil R 972 as flow-enhancing additives, both by Evonik.…”