The concept of additive manufacturing often conjures up images of sintering powder to create small parts. RAMLAB, based out of Rotterdam, Netherlands, is scaling up that imagery significantly by using wire arc additive manufacturing (WAAM) to 3D print metal ship propellers. The first propeller made using this approach was created last year thanks to a consortium that includes RAMLAB, Damen Shipyards Group, Promarin, Autodesk and Bureau Veritas.
“We focused on WAAM technology because we are in the ports, and our customers and clients are working in the ports making large parts. The only applicable application to do two or three different things is WAAM,” said Vincent Wegener, RAMLAB managing director.
Casting, which is the traditional method used to create propellers, requires long lead times since the process involves making a mold, casting it, and then processing it. Wegener noted that most forging and casting companies are no longer located in Europe, which means even more time is needed to get parts. Additionally, most of those companies require orders for quantities larger than one part, which means warehousing a large stock of components that many never be used.
From a supply chain view, the switch to WAAM curtails many of the costs associated with casting methods.
“You have a relatively low-cost machine with relatively low-cost materials—the wires are cheaper if you compare to powders—so per kilo, you are better off than powder in this case,” Wegener said. “This makes it possible to compete with existing technologies.”
For RAMLAB, one of the main draws of WAAM was that the company was already using welding robots, so it was a familiar technology. RAMLAB then incorporated Autodesk PowerMill software, which makes it possible to weld complex geometries into the software used by the robots. Wegener said the company makes its strategy in PowerMill, then loads that strategy into robotic software to weld their shapes.
Another main appeal of this technology is its scalability. The robots can be put on a 6-meter track, which gives lab workers a reach of about 6 by 2x2 meters. So, just how big a part can they make?
“We think about 1 to 10 meters is about the scalability of this technology,” Wegener said.
As with any new method, there are some downsides, the biggest of which is time. Considerations have to be made about how many kilos can be melted in an hour. Another challenge lies in the heat factor—cooling time must be figured into the production process. The lack of porosity issues with casting and better control over quality make these constraining factors manageable.