In-situ spatio-temporal monitoring of heat transfer in pre-sintered powder in powder bed fusion: electron beam

In-situ sensing and monitoring techniques for heat transfer characterization in powder bed fusion have gained considerable attention within the additive manufacturing community. Indeed, by analysing heatmaps and thermal gradients, researchers aim to detect local anomalies and predict the resulting microstructural properties of the part. However, existing approaches focus on generating spatial and temporal heat maps only within regions of the powder bed where selective melting is applied. On the contrary, heat dissipation into the surrounding powder has received little or no investigation. Variations in heat transfer in the surrounding powder can adversely affect surface finish, dimensional accuracy, and microstructural consistency. To address this gap, the present study proposes a novel approach for in-situ monitoring of heat transfer outside the solidified area, specifically designed for powder bed fusion—electron beam (PBF-EB). The method integrates spatio-temporal modelling of the thermal history, based on a two-dimensional distance transform map, with a non-linear, low-dimensional learning technique capable of distinguishing between normal and anomalous heat transfer into the powder. The approach is demonstrated in a real PBF-EB case study using pure copper, a material whose pronounced thermal conductivity contrast between the consolidated bulk and the surrounding powder is a potential source of defects, thus motivating the study of new in-situ thermal monitoring strategies.