Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing (AM) technique that enables the fabrication of complex, detailed metal components. However, processing pure copper via LPBF presents significant challenges due to its high reflectivity to infrared laser wavelengths. This leads to poor laser absorption during processing, resulting in unstable melt pools and porosity defects in the finished part. In the current state-of-the art, copper LPBF is capable in producing dense parts (>99.6%) with high thermal conductivity (>100%IACS). However, this success relies on the use of high Line Energy Densities (LED) leading to a keyhole melt pool which allows multiple internal reflections. As a result of the high LED, large melt pools are created which limits the degree of details that can be achieved in copper LPBF. Previous studies have suggested changes in three main categories to improve absorptivity in pure copper LPBF: Laser source wavelength, process parameters and powder modifications.

This work focusses on quantifying the total laser absorption based on calorimetry experiments performed during the LPBF process of pure copper. Because the experiments are performed while processing, the measured absorptivity includes both the effect of laser-powder and laser-melt interactions. The effect of process parameters (laser power, scan velocity, layer thickness and hatch distance) and powder modifications (Powder Size Distribution (PSD) and powder surface modifications) on the absorptivity is reported. By systematically analyzing these factors, this study aims to enhance process stability and reduce melt pool dimensions in Cu LPBF manufacturing, while maintaining the performance of the state-of-the-art.