Material extrusion additive manufacturing of stainless steel gyroid tubular structures for fluid applications

High-performance tubular mixers and heat exchangers, leveraging intricate internal geometries such as gyroid structures, represent a promising avenue for enhancing thermal and fluidic efficiency across various industrial sectors. These components typically require the typical geometric complexity and internal resolution achievable only through metal Additive Manufacturing (AM), with Laser Powder Bed Fusion (LB-PBF) being the most established process. However, LB-PBF is associated with high production costs, limiting broader industrial adoption. Material Extrusion of metals based on polymeric feedstock (MEX-TRB/M), is an emerging and cost-effective metal AM process that offers a potentially viable and more sustainable alternative for fabricating such components. Yet, its lower dimensional accuracy and surface quality – particularly in internal features – pose challenges that have thus far restricted its use to prototyping. This study examines the feasibility of using feedstock metal extrusion to fabricate tubular structures with gyroid infill and systematically analyzes how key printing parameters, such as layer height and part orientation, affect critical quality metrics, including internal surface roughness, dimensional accuracy, and production efficiency. CT scan-based dimensional analysis confirms that MEX can reliably produce these complex structures, though deviations in relative density require careful process tuning. The study further evaluates how these quality indicators affect functional performance through low-pressure water flow experiments, highlighting correlations between internal roughness and pressure drop behavior. Based on these insights, optimal printing strategies are proposed to balance the trade-off between performance and productivity. By providing a comprehensive assessment of feedstock metal extrusion for complex gyroid-based heat exchangers and mixer components, this work advances the path toward industrial adoption of this technology and demonstrates its potential as a cost-effective alternative to LB-PBF when process-specific guidelines are applied.