Selective laser sintering (SLS) is a key additive manufacturing (AM) technology for fabricating complex polymer components. Polyamide 11 (PA11), a semi-crystalline biopolymer derived from castor oil, has gained attention due to its sustainability and excellent mechanical properties [1]. However, its sensitivity to thermal effects in SLS processing leads to discoloration associated with thermo-oxidative degradation [2, 3].
This study investigates the influence of laser energy density and build chamber placement on discoloration of PA11 SLS parts. Both factors affect temperature, driving degradation and discoloration, with their correlation to mechanical and dimensional properties also examined [4, 5]. Experimental work utilized a design of experiments (DoE) approach to vary energy densities and component placements. Results revealed a strong correlation between energy density and discoloration, with higher energy densities leading to increased yellowing. Build placement significantly influenced thermal profiles, with components at the chamber center showing greater discoloration due to higher and prolonged temperatures.
Two models were developed to understand these challenges. A regression-based model was created to predict discoloration based on energy density and placement, demonstrating high accuracy within the pre-defined domain. Next, a novel numerical thermal model was developed to predict discoloration for any geometry, integrating an Arrhenius-based degradation framework. Our work demonstrates that this numerical model successfully correlates the simulated thermal history with discoloration and enables predictions for new parts.
This work enhances understanding of PA11 SLS processing and provides predictive frameworks for mitigating discoloration and optimizing part quality across varying geometries.