A prototype of the world's first class approved ship propeller has been produced using 3D printing techniques. The 1,350mm diameter propeller, named "WAAMpeller", is the result of a cooperative consortium of companies that includes RAMLAB, Promarin, Autodesk, Damen Shipyards Group 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 a Damen tug. With production complete, the WAAMpeller will be CNC milled at Autodesk's manufacturing facility in Birmingham, UK.
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," said 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," added Custers.
"Material characterisation and mechanical testing have been an important part of this project," said 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."
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," said Custers. "We are aiming to install this second one onto one of our tugs later this year."
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