Influence of the scan pattern on the melt pool temperatures and the mechanical properties of thin-walled components in Laser-based Powder Bed Fusion of Polyamide 12

In laser-based powder bed fusion of plastics, the mechanical properties are geometry-dependent, which poses a challenge for producing lightweight, thin-walled aerospace and automotive components. To investigate this issue, this study utilized infrared thermography data to monitor the production of tensile test specimens with varying cross-sections and energy input. The thermographic measurements reveal accelerated cooling at the sample edges, even with contour exposure. This is because the cooling behavior is related to the sample's geometry and scan pattern. Additionally, using x-y-Alternating scan vectors results in layer-wise peak temperature variations, which correlate with the scan vector length and lead to higher porosity in corresponding layers. Consequently, reducing the energy input or the thermal overlap frequency in layers with short scan vectors and samples with small cross-sections leads to a porous boundary region, ultimately reducing their mechanical properties. This demonstrates that the scan pattern contributes significantly to the geometry-dependency of mechanical properties.