Printing aluminium has always been a trade-off between printability and performance. Molten Metal Deposition (MMD) ends the compromise by letting engineers use the alloys they actually need.
A mismatch between process and material
Aluminium is used everywhere: in aerospace, automotive, electronics and energy. It’s lightweight, corrosion-resistant and highly conductive. But while conventional processing is relatively straightforward, Additive Manufacturing (AM) has long struggled to handle aluminium correctly.
The issue isn’t the material itself, but the processes used to print it. Powder Bed Fusion (PBF) struggles with aluminium’s high reflectivity and thermal conductivity, requiring intense energy input to sustain melt pools. Wire-based processes like WAAM are more stable, but sacrifice resolution and process control.
The result: most AM systems fall back on an artificial, non-standard alloy like AlSi10Mg, paired with expensive inert chambers, preheating routines and thermal post-processing that reduce the technology’s value in real production environments.
Molten Metal Deposition breaks this cycle. By extruding aluminium in its molten state, it eliminates the friction that kept the material on the fringe of AM. For the first time, standard industrial alloys, not just printable variants, can be used safely, economically and without compromise.
What is Molten Metal Deposition?
Molten Metal Deposition is an additive process that extrudes molten aluminium directly from a heated nozzle. It avoids the high-energy beams or arcs used in most metal AM processes, and eliminates the need for a post-sintering phase.
Unlike PBF or Direct Energy Deposition (DED), no high-energy beam or arc is needed during deposition. And unlike Binder Jetting (BJ), there’s no post-sintering phase required to sinter the part. The material is already in its most reactive and cohesive state, ready to form clean metallurgical bonds as it solidifies.
Instead of relying on local point heating, the system works through bulk heating of a crucible. The thermal profile is entirely different: more predictable, lower maximum temperatures and lower thermal gradients. The process operates in ambient or local-protective conditions, uses off-the-shelf aluminium wire, and avoids the oxidation risks, contamination, or explosion hazards of powder-based systems.
Why aluminium has resisted traditional AM
Three core properties make aluminium hard to 3D print using conventional AM methods:
- High thermal conductivity: aluminium rapidly dissipates heat, making it difficult for beam-based processes to sustain melt pools.
- Low viscosity in liquid form: it tends to flow uncontrollably if not carefully confined, which complicates layer formation.
- Susceptibility to oxidation: in powder form, aluminium oxidises aggressively, requiring inert environments and strict powder handling protocols.
These traits leave a narrow operating window. Beam-based systems must balance power to avoid defects like keyholing, while still achieving proper fusion. Even then, commonly used alloys like Al-6061 or Al-7075 crack or distort due to residual stress.
That’s why most systems rely on AlSi10Mg. It prints cleanly, but its mechanical properties and post-processing requirements limit its use in production.
How Molten Metal Deposition changes the equation
Molten Metal Deposition avoids these limitations entirely. By keeping aluminium in its molten state throughout deposition, it removes the need to create and stabilise a melt pool during printing. This enables more controlled cooling rates, lower internal stress and higher success rates with crack-prone alloys.
Because the material is already cohesive, there’s no porosity from under-fused powder or arc-based splatter. The slower, more uniform solidification supports structural consistency and anisotropy.
It also changes what goes in. Standard aluminium (welding) wire, readily available, affordable and certified, replaces expensive atomised powder. This reduces costs and streamlines QC and downstream processing, since teams are already familiar with these alloys.
Reintroducing real-world alloys
Traditional AM workflows have prioritised printability over usability. Alloys like AlSi10Mg print well but are not industry standards. Molten Metal Deposition reverses this trade-off.
Alloys such as Al-4043, Al-6061, Al-6082 and Al-7075, standard in aerospace, automotive and structural design, can now be printed without cracking or distortion. This eliminates the need to validate a foreign material or simulate its behaviour. The result is tighter alignment between prototyping and production: one alloy, one process, one outcome.
Simplifying the thermal model
Unlike beam-based systems that rely on complex energy calibration, Molten Metal Deposition simplifies the entire thermal model. There’s no laser, no arc, no melt pool to manage. The material is already molten. Instead of controlling energy input, the process focuses on deposition and cooling, avoiding many of the failure modes associated with beam-based printing.
It also simplifies infrastructure. Printing takes place in ambient air or a local inert atmosphere. No vacuum chambers and repetitive inert gas purging. No post-build thermal stress relief. No hipping. What comes off the substrate is dimensionally stable and structurally coherent.
Efficiency, not just feasibility
Molten Metal Deposition is a practical method for making production-grade aluminium parts: faster, cheaper and safer.
Because the input is wire, not powder, material waste is minimal. There are no recoaters, vacuum pumps or powder traps. The process can be paused and resumed without batch constraints. The system footprint is small. Safety risks are low.
Even when extra machining is needed for surface finish or tolerances, the overall part cost remains significantly lower than PBF or WAAM, especially in low-volume or custom applications where cost per part matters more than throughput.
Where Molten Metal Deposition makes sense
Molten Metal Deposition excels in sectors where aluminium is already established, but traditional AM has fallen short.
- Aerospace and defence benefit from the ability to print complex aluminium structures in industry-recognised and certified, high-strength alloys without residual stress, including brackets, antenna supports, payload enclosures and UAV airframes.
- Automotive sees use in heat exchangers, pump housings and custom ducting, where part weight, airflow and thermal transfer are critical. Molten Metal Deposition supports the geometries needed for those functions without compromising strength.
- Electronics gain from printed heatsinks, cold plates and housings designed for thermal regulation and compact integration. Aluminium’s conductivity can finally be harnessed in AM without reliability issues.
- Architecture and design use the process for large-format, unsupported structures in real aluminium. Lighting, sculpture and façade elements benefit from the strength, durability and finish quality the process allows.
How it compares to other aluminium AM methods
| Feature | Molten Metal Deposition | Powder Bed Fusion | Wire Arc AM |
| Alloy compatibility (Al-6061, Al-7075) | High | Low | Low |
| Process atmosphere | Open-air or local athmosphese | Inert chamber | Local athmosphese |
| Input material cost | Low | High | Low |
| Energy consumption | Low | Very high | High |
| Post-processing needs | Minimal | Extensive | Moderate |
| Oxidation risk | Low | High | Low |
| Resolution and finish | Medium | High | Low |
| System complexity | Low | High | Low |
| Safety considerations | Minimal | High (ATEX) | Minimal |
For whom is it?
ValCUN’s implementation of Molten Metal Deposition is already in use by aerospace and defence organisations who need to produce aluminium parts on demand, outside of controlled lab environments.
For these users, systems must be compact, certifiable and easy to run in varied conditions. MMD meets that requirement. It enables structural aluminium components to be printed on-site, with minimal infrastructure or peripherals.
Other applications include industrial OEMs pursuing energy-efficient fan blades for eg. datacenters and electronics manufacturers optimising internal heat management with geometries impossible to produce using conventional methods.
A better way, not just a new one
Molten Metal Deposition isn’t about expanding the boundaries of AM. It’s about making aluminium work in practice.
It shifts the focus from showcase parts in exotic alloys to functional components in the alloys teams already qualify, machine and assemble. It puts aluminium back into additive workflows that depend on material compatibility, stable output and cost control.
Conclusion
The barrier to printing aluminium wasn’t a lack of innovation. It was a mismatch between material and method. For years, additive manufacturing has tried to force aluminium into processes that were never suited to its properties.
Molten Metal Deposition corrects that. It deposits real industry alloys in molten form, controls the flow rather than forcing the fusion, and removes the powder-handling, atmospheric and thermal challenges that made aluminium AM impractical at scale.
That’s not a revolution. It’s a correction. And it’s 35 years overdue.
