A Comprehensive Review of Metal Filament Extrusion (MFE) for Metal 3D Printing: Processes, Challenges, and Future Directions

Abstract Metal Filament Extrusion (MFE), is a promising low-cost metal additive manufacturing (AM) technique that combines extrusion-based 3D printing with sinter-based densification. The review outlines the MFE workflow in detail, with emphasis on feedstock design, extrusion-based printing techniques, binder removal, and the sintering stage. Key aspects such as dimensional accuracy, sintering shrinkage (typically 15–20%), and mechanical properties especially tensile strength are critically examined. The inherent challenges of the MFE process include non-uniform shrinkage, porosity, incomplete debinding, and thermal distortion, which significantly affect final part quality. The review further explores recent advancements aimed at improving debinding efficiency, optimizing sintering profiles, and compensating for dimensional changes through design and simulation. Particular attention is given to defect mitigation strategies, including binder formulation, multi-step debinding, and part orientation. By analyzing current trends and limitations, this work identifies future directions for research in improving accuracy, strength, and reliability of MFE-fabricated metal components, making it a viable alternative to more costly metal AM methods like SLM or Binder Jetting.