The 1,350mm diameter propeller – named WAAMpeller – is the result of a cooperative consortium of companies that includes Damen Shipyards Group, RAMLAB, Promarin, Autodesk and Bureau Veritas.
The WAAMpeller was fabricated from a Nickel Aluminium Bronze (NAB) alloy at RAMLAB (Rotterdam Additive Manufacturing LAB) in the Port of Rotterdam. The propeller was produced with the Wire Arc Additive Manufacturing (WAAM) method using a Valk welding system and Autodesk software. The triple-blade structure uses a Promarin design that is used on Damen’s Stan Tug 1606. With production complete, the WAAMpeller will be CNC milled at ‘Autodesk’s Advanced Manufacturing Facility in Birmingham, UK’.
Materials science
This prototype 3D printed propeller represents a steep learning curve of the understanding of material properties. “This is because 3D printed materials are built up layer by layer,” says Kees Custers, Project Engineer in Damen’s R&D department. “As a consequence, they display different physical properties in different directions – a characteristic known as anisotropy. Steel or casted materials, on the other hand, are isotropic – they have the same properties in all directions.”
Because of this critical difference, one of the first steps was to carry out extensive testing of the material properties of the printed material to ensure compliance to Bureau Veritas standards. “This involved printing two straightforward walls of material – then using a milling machine to produce samples for lab testing of tensile and static strengths.”
It can also be said that the 400kg WAAMpeller sets a milestone in terms of 3D printing production techniques. “The challenge has been to translate a 3D CAD file on a computer into a physical product. This is made more complex because this propeller is a double-curved, geometric shape with some tricky overhanging sections,” explains Mr Custers.
Yannick Eberhard from Promarin’s R&D department adds that “the transformation from a semi-automatic to robotic processing is the solid foundation for even more complex and reliable future propeller designs“.
Great potential
“Material characterization and mechanical testing have been an important part of this project,” says Wei Ya, Postdoctoral Researcher from the University of Twente at RAMLAB. “We have to make sure that the material properties meet the needs of the application. Material toughness, for example – ensuring that the propeller is able to absorb significant impact without damage.”
“But we have also been working towards optimising the production strategy for 3D metal deposition. This includes bead shape and width, as well as how fast we can deposit the printed material.”
Highlighting RAMLAB’s capacity to print objects with maximum dimensions of 7x2x2 metres, Mr Ya says: “For large scale 3D metal deposition, the WAAMpeller is really ground-breaking for the maritime industry.”
“This technology is a fundamental change in the concept of how we make things. With additive manufacturing, you can print most metallic components that are needed in principle. There is so much potential for the future – these techniques will have a big impact on the supply chain.”
Class approval
This first prototype WAAMpeller will be used for display purposes, and planning for a second example is already underway. “We start production of a second propeller with class approval later next month – using all the lessons we have learned over the past few months,” notes Mr Custers. “We are aiming to install this second one onto one of our tugs later this year.”