MX3D offers WAAM-printed bronze ship propellers without patterns, with DNV AMC3 backing

MX3D prints custom ship propellers in nickel aluminum bronze with wire arc additive manufacturing, skipping the casting pattern and mold. A five-blade, 200 kg propeller took 80 hours, and the company says it is the first WAAM facility certified to DNV AMC3. The route targets one-offs, urgent replacements and repairs.

Context WAAM (wire arc additive manufacturing) is a directed energy deposition process in which a robot-held arc welding torch melts metal wire and builds a part layer by layer.

Why print a propeller instead of casting it?

Conventional propellers are cast in a sand mold made from a pattern, then machined and ground. That pays off for series of identical units, because the pattern cost is spread over many parts. For a single unit the pattern, the mold and the wait for foundry capacity add cost and time. MX3D builds the blades and hub directly from a 3D model with a robot, using CuAl8Ni6 wire, and then machines and balances the result to the customer's specification. The company quotes a deposition rate of 2 to 8 kg of metal per hour.

Where does WAAM fit best?

MX3D names several cases: one-off propellers and small batches, urgent replacements when the pattern is lost or the maker no longer supplies the part, single blades for controllable-pitch propellers and thrusters, and trials of new blade designs. Hollow blades are possible, which a foundry cannot cast. The same robot process also repairs propellers: the damaged propeller is scanned, the area ground clean, material is deposited where it is missing, and the blade is machined back to profile, dye penetrant tested and rebalanced. Other weldable alloys such as CuNi 70/30, stainless steel and duplex are available for other seawater parts.

What about class rules and certification?

Classification societies share common rules for propeller bronze, written for cast parts. A printed propeller therefore goes through the society's route for additively manufactured parts, with approval per propeller or application and a plan agreed with the surveyor beforehand. MX3D says a WAAM propeller first received class approval in 2017 and that Lloyd's Register and ABS have since recognised printed propellers. Accuracy follows ISO 484, with a class chosen by the customer. MX3D reports that all printed NiBrAl test specimens beat the class minimums for tensile strength (above 715 MPa against 590 MPa) and elongation (30% against 16%).

How is quality checked?

The company's MetalXL software logs process data for each layer, including interpass temperature, wire feed, electrical values and torch position, and maps it onto the 3D model. This shows thin or thick areas, indicates density and tells inspectors where to look. After machining the part is scanned against the model, then tested with visual and dye penetrant inspection, with ultrasonic or radiographic testing where required, and statically balanced. Destructive tests on pieces printed in the same build are available on request. MX3D holds ISO 9001 certification from DNV and an LRQA AM facility qualification.

What it means

For shipowners and yards, the business case rests on avoiding pattern cost and foundry queues, so it fits one-offs, spares for out-of-production designs and repairs rather than series. The approval route is the main planning item: class societies approve per propeller or application, so surveyor involvement and a qualification plan should be factored in early. The strength figures are the supplier's own and class acceptance remains case by case. Hollow-blade designs may be the more interesting long-term option for smaller operators.

Frequently asked questions

How long does it take to print a WAAM ship propeller?

MX3D printed a five-blade, 200 kg nickel aluminum bronze propeller in 80 hours, and says printing takes days rather than months.

Can a damaged propeller be repaired with WAAM?

Yes. MX3D scans the propeller, grinds the damaged area clean, deposits material where it is missing, then machines the blade back to profile, tests it and rebalances it.

What does DNV AMC3 mean?

It is the highest class in DNV-ST-B203, the DNV standard for 3D printed metal parts, covering critical, high-load parts. MX3D says it is the first WAAM facility certified to it.