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Robotics and 3D Printing Go Large Together

Maritime industry gets disrupted with a first-ever 3D printed ship’s propeller

On-demand maritime parts
It’s always an exciting exercise when robotics and 3D printing go large together, especially when it’s to build something never before attempted.

It’s even more exciting when that something turns out to be 4.5 feet wide (1.35 meters) and weighs in at over 800 lbs. (400 kg). Better yet, if the finished something is ready to go to market and is easily reproducible, then the merely exciting becomes the very extraordinary.

A Dutch marine lab, RAMLAB (Rotterdam Additive Manufacturing Laboratory), has pulled off the very extraordinary with a 3D-printed, first-ever ship’s propeller.

That it’s a propeller as a finished product makes it saleable the world over to a marine propeller market that’s projected to reach $5.37 billion by 2022 ($4.73 billion in 2017).

In addition to being a finished product, it’s also the result of a readily reproduceable, additive manufacturing (AM) process that anyone anywhere can replicate. RAMLAB used a 6-axis  Panasonic TAWERS welding robot and a print head from Valk Welding.

All of which means goodbye (eventually!) to inventories of warehoused propellers waiting for customers, or worse, the glacial process of building a mold and casting a propeller. “The propeller was fabricated from a nickel-aluminum-bronze alloy and produced with the Wire Arc Additive Manufacturing method [hence its name, WAAMpeller] using an electric arc welding system from Valk Welding and Autodesk’s Powermill software, which worked out the computer-aided manufacturing (CAM) strategy for the propeller’s curved geometry.”

The triple-blade WAAMpeller was essentially a single continuous weld in 298 layers (1.5 miles long) of a molten nickel-aluminum-bronze bead deposited by the welding head, working continuously for 256 hours, which tallies out to about 10.5 straight days of non-stop printing.

Disrupting the marine industry
Although robots as 3D printers have been around for a while, especially in aerospace, automotive, and construction, the marine industry has been relatively free from 3D printing disruption, especially large-scale parts.  The WAAMpeller is a first for the marine industry; and RAMLAB is hoping for more opportunities to apply the technology.

Kelvin Hamilton, senior technical consultant at Autodesk, initiated the idea of printing a propeller: “I thought a propeller would be an intriguing geometry to tackle with additive manufacturing; it has complex curves and has to endure severe stresses in service.”

Damen Shipyards, RAMLAB’s partner, commissioned a 3D printed tugboat propeller, in a venture with RAMLAB and one of its owners, the Port of Rotterdam, Promarin, the German propeller and marine technology company; Autodesk and Bureau Veritas, the latter being the Dutch marine testing, inspection and certification house whose job it was to certify the finished prop for port and sea duty.

We know welds are strong, and WAAM essentially makes a single continuous weld, so we thought it would be OK, but we still had to prove it,” Hamilton said. “We did the entire manufacture for this item, but I think its real strength will come in maintenance; if a propeller is damaged, for example, a piece gets knocked out of a blade or a blade gets deformed, we will be able to grind away the damaged part and print directly on top to reform it.”

“That will be much faster and cheaper, and potentially stronger too,” added RAMLAB co-founder and managing director Vincent Wegener.

Another plus for the WAAM process, say the developers, is that the parts produced from the process are hollow. The hollow WAAMpeller is therefore lighter than a cast propeller, which enables a vessel to use less fuel.

The WAAMpeller process created a propeller with a deeply ridged surface resulting from the deposition of layer upon layer of molten alloy (see photo). To finish the surface to a smoother end product ready for inspection took three days of hand grinding. In the future, CNC milling will be used. Hamilton says the cast propellers are generally hand-ground, so “for the purposes of certification we wanted to keep one part of the manufacturing process the same; everything else is different.”

Certified for sea duty
With the WAAMpeller installed on a Damen Stan Tug 1606 (see video), the project progressed to the testing stage that included speed trials, a bollard pull (pulling power of a stationary watercraft) and crash stop testing.  

 “Of course, we were all a bit nervous beforehand,” admitted Kees Custers, Damen R&D engineer, “after all, innovation always comes with a certain amount of unknowns – but the testing was a success.”

“We are pleased to report that the WAAMpeller displayed the same behavior as a conventional casted propeller in all of the tests. This includes the same level of performance in the crash stop scenario, which – going from full throttle ahead to full throttle reverse – is the heaviest loading that a propeller can experience.”

What next?
With the Earth some 71 percent water, boats, ships, and other water craft above and below the surface need propellers for propulsion, so the future of the WAAMpeller seems unlimited.

A new industry has been birthed. RAMLAB-type clones will undoubtedly pop up all over the world to copycat the WAAM process or to maybe even better it.

In the future, the build and milling time will undoubtedly get sped up a bit; maybe two or even three robot printers could be used simultaneously.

For sure, the hollow WAAMpeller has earned a place for itself in the maritime industry. Of course, beyond what Bureau Veritas can ascertain, the real test of the 3D printed propeller will come from in-use testing and trials over time.

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