In-process rheological assessment of recycled ABS-GF in large format additive manufacturing

Abstract Large Format Additive Manufacturing (LFAM) has made considerable progress in recent years and is now considered a reliable method of fabricating components with demanding structural requirements. The drive towards more sustainable manufacturing methods has highlighted the significance of integrating circular economy principles into the processes of developing materials and executing production workflows. However, the effective utilisation of recycled materials, particularly fiber-reinforced composites (FRCs), remains technically challenging, especially with regard to preserving mechanical performance across multiple reuse cycles. This study therefore proposes a new methodology focused on the real-time rheological assessment of recycled acrylonitrile-butadiene-styrene reinforced with short glass fibers (ABS-GF) within LFAM processes. Material flow is estimated by relating printer torque data to rheological measurements, enabling in-process insight during printing. These rheological parameters are closely linked to key printing qualities, such as layer adhesion, dimensional accuracy, and overall structural integrity. It is observed that the torque required for recycled material is approximately 50% lower than for virgin, indicating reduced viscosity and altered flow dynamics. Despite this, mechanical performance shows only a moderate decrease in tensile strength, with slight variation in the different printing directions. Due to property variations caused by thermo-mechanical degradation across recycling cycles, the research outlines future steps to extend this method to broader material classes and implement adaptive control mechanisms. These measures aim to adjust process parameters dynamically, ensuring consistent quality and reliable adhesion even when recycled feedstocks vary. This addresses a central challenge in advancing sustainable LFAM applications.