Efficient continuum-based modelling and analysis of polymer SLS: Insights into particle sintering and densification in straight and corner scanning passes

Selective Laser Sintering (SLS) is a widely used additive manufacturing technique that enables the production of complex polymer components. However, the sintering process involves complex thermal and material flow interactions that influence densification, shrinkage, and hence final part quality. This study presents a novel continuum-based numerical model for polymer SLS, validated through experimental investigations using PA12 powder. The model captures key sintering characteristics, including heat accumulation, powder shrinkage, and densification, at a fraction of the computational cost of traditional Discrete Element Method (DEM) approaches. A key finding of this study is the identification of oversintering effects at sharp corners, where heat accumulation leads to increased strand width and unexpected material redistribution—an effect not previously reported in the literature. Experimental validation confirmed good agreement with numerical predictions. However, deviations in strand thickness at sharp corners suggest that capillary-driven melt redistribution may play a role, which cannot be captured without resorting to more computationally intensive particle-level models. This work demonstrates the potential of continuum-based modelling for predicting sintering behaviour in SLS while maintaining computational efficiency. The model offers a valuable tool for exploring process parameters and optimising print path strategies, ultimately contributing to industrialisation of polymer SLS.