Metal Additive Manufacturing Through Screw Extrusion: State-of-the-Art and Future Prospects

Additive manufacturing (AM) is emerging as a key technology for advanced manufacturing and innovation. Among AM processes, extrusion-based techniques are gaining interest for metals, given their lower equipment cost and easier operation compared to methods like laser powder bed fusion. This review examines recent research on screw extrusion AM for metals in the semi-solid state. Process parameters such as nozzle diameter, extrusion speed, and standoff distance significantly influence the quality of printed beads and tracks. Smaller nozzles (approximately 1 mm) and moderate speeds (around 10 mm/s) are suitable for printing metals like aluminum alloys with a semi-solid fraction of around 0.4. Surface quality remains a challenge, affected by parameters like layer height, temperature, and feedstock properties. Quantifying and optimizing extrusion process parameters is critical for balancing deposition rates and quality. Overall, screw extrusion AM shows promise for printing metals in the semi-solid state, but further research is needed on thermal control, extruder design, and bead uniformity to enable industrial adoption.