Laser-based powder bed fusion (PBF-LB) is a key metal Additive Manufacturing (AM) technology offering high production flexibility and design freedom. However, the complex process can result in significant differences in thermal history within a part, causing deviations in mechanical properties [1]. Accurate numerical modelling approaches are essential to enable prediction and prevention of these deviations in thermal history and mechanical properties. This study focuses on part-scale simulation techniques in PBF-LB and how state-of-the-art modelling methods can be employed in process optimisation to limit thermal history variability in complex geometries. In this study, a part-scale thermal finite element (FE) model was developed to model the PBF-LB process in a computationally efficient way. First, the model was calibrated and validated experimentally using Long-Wave Infrared (LWIR) camera data obtained during the PBF-LB process. Secondly, improvements of a previously developed process optimisation framework were made, utilising the part scale thermal finite element model to optimise inter-layer time (ILT) and local laser power to mitigate thermal variations and promote homogeneous material properties [2]. The improved framework's effectiveness was demonstrated through experimental validation on a complex topology optimised aerospace bracket, using (LWIR) and Near Infrared (NIR) camera measurements. The study showcases the application of physics-based modelling to predict and homogenise thermal history at the part-scale. The results highlight the benefits of combining simulation and in-situ monitoring for validation of thermal FE models and developing model-based variable parameter approaches. This research contributes to the development and application of predictive computational modelling approaches for PBF-LB towards efficient process-based qualification and certification methods for AM parts. [1] J. Munk, E. Breitbarth, T. Siemer, N. Pirch, and C. Häfner, ‘Geometry Effect on Microstructure and Mechanical Properties in Laser Powder Bed Fusion of Ti-6Al-4V’, Metals, vol. 12, no. 3, Art. no. 3, Mar. 2022, doi: 10.3390/met12030482. [2] T. Koenis, E. Haumahu, M. Montero-Sistiaga, and M. de Smit, ‘Model-Based Process Optimisation Framework for Variable Process Parameters Towards Homogeneous Ti-6Al-4V PBF-LB Aerospace Components’, in 7th Fraunhofer Direct Digital Manufacturing Conference, Berlin, Mar. 2025.