  This study presents novel predictive models using Graph Neural Networks
(GNNs) for simulating thermal dynamics in Laser Powder Bed Fusion (L-PBF)
processes. By developing and validating Single-Laser GNN (SL-GNN) and
Multi-Laser GNN (ML-GNN) surrogates, the research introduces a scalable
data-driven approach that learns fundamental physics from small-scale Finite
Element Analysis (FEA) simulations and applies them to larger domains.
Achieving a Mean Absolute Percentage Error (MAPE) of 3.77% with the baseline
SL-GNN model, GNNs effectively learn from high-resolution simulations and
generalize well across larger geometries. The proposed models capture the
complexity of the heat transfer process in L-PBF while significantly reducing
computational costs. For example, a thermomechanical simulation for a 2 mm x 2
mm domain typically requires about 4 hours, whereas the SL-GNN model can
predict thermal distributions almost instantly. Calibrating models to larger
domains enhances predictive performance, with significant drops in MAPE for 3
mm x 3 mm and 4 mm x 4 mm domains, highlighting the scalability and efficiency
of this approach. Additionally, models show a decreasing trend in Root Mean
Square Error (RMSE) when tuned to larger domains, suggesting potential for
becoming geometry-agnostic. The interaction of multiple lasers complicates heat
transfer, necessitating larger model architectures and advanced feature
engineering. Using hyperparameters from Gaussian process-based Bayesian
optimization, the best ML-GNN model demonstrates a 46.4% improvement in MAPE
over the baseline ML-GNN model. In summary, this approach enables more
efficient and flexible predictive modeling in L-PBF additive manufacturing.
