Modelling laser beam absorption for powder-based sintering

Additive manufacturing techniques like selective laser sintering face challenges such as residual stresses and warping. Understanding laser-powder interaction is crucial to addressing these issues. This pa-per presents a computational model to simulate laser energy propagation and absorption in a particle bed during early sintering stages. A ray tracing model, developed in MATLAB®, simulates light propagation through 2D and 3D particle beds. The 2D model is used to identify several numerical parameters for the 3D model, which is applied to a particle doublet. Its results are then used for mechanical sintering simulations in MercuryDPM. These model predictions are compared to experimental data on the sintering of polystyrene particles. The model is extended to a full 3D particle bed used to derive equations which can efficiently estimate absorbed energy per particle based on material, geometric, and laser parameters. A semi-random walk is also introduced, simulating light propagation stochastically while significantly reducing computation time. This stochastic approach yields energy distributions in the particle bed comparable to ray tracing but is 1000 times faster. Lastly, equations are derived that replace the simulations, further reducing the compu-tation time by a factor of 70, making them suitable for transient sintering simulations.