Understanding Geometry Dependent Temperature Fields in Laser Powder Bed Fusion of PA12 by Means of Infrared Thermal Imaging

Laser powder bed fusion of polymers (LPBF) is a promising additive manufacturing technology that allows for the generation of complexly shaped parts with high mechanical properties. However, enhancing the reproducibility of part properties is one of the main challenges on the technologies way to industrialization. Therefore, the process has to be robust, the resulting part properties must be predictable and reproducible. The basic material-beam-interactions have to be analyzed to assess the impact of geometry dependent temperature history on part properties. Within this contribution, the influence of part geometry at constant surface area on temperature fields and layer formation is investigated. Besides quadratic cross-sections, triangular, round, oval and hollow structured geometries are considered. Infrared thermal imaging measurements were conducted during exposure to identify variations of the transient temperature levels. The fabricated parts were fundamentally characterized to correlate the temperature values to part properties. It is clearly visible that the scan vector length is decisive for the resulting temperature level and an impact on the part properties is observable at monolayer level. The results indicate that exposure parameters should be optimized with regard to the particular layer geometry, especially for high variations of the cross-sectional area.