University of Manchester maps molten metal deposition defect physics

A recent study from The University of Manchester, published in Materials & Design, has revealed that minor variations in nozzle and substrate temperature during molten metal deposition (MMD) critically influence the quality of 3D-printed aluminum parts. The research focuses on aluminum alloy 4043 and provides engineers with a physics-based understanding of how to control defects and microstructure in this emerging additive manufacturing process.

The MMD process, developed by ValCUN BV, is designed for affordability and ease of deployment. The study found that higher nozzle and substrate temperatures led to slower cooling rates, resulting in coarser grain structures and increased porosity—tiny internal voids that compromise a part's strength. Conversely, cooler process temperatures accelerated solidification, producing finer grains and fewer defects.

Researchers observed a strong correlation between grain size and porosity, meaning a single process parameter could influence both simultaneously. Furthermore, defect levels and grain size generally decreased as the build progressed through successive layers. This indicates that thermal conditions are not static during printing but evolve as the part grows and its heat dissipation changes.

Notably, the printed samples, despite some porosity, exhibited hardness and elastic modulus values comparable to conventionally manufactured parts. This suggests that while temperature control is crucial for defect reduction, the process can still yield components with acceptable mechanical performance. The findings offer a foundation for manufacturers to deliberately tune MMD builds, moving beyond trial and error for more reliable aluminum components.