A future involving 3D-printed components on board commercial vessels has moved a step closer to reality
A prototype of the world’s first class-approved ship’s propeller produced using 3D printing techniques has been completed.
The 1,350 mm diameter propeller – named WAAMpeller – is the result of a co-operative consortium of companies that includes Damen Shipyards Group, RAMLAB (Rotterdam Additive Manufacturing Lab), Promarin, Autodesk and Bureau Veritas.
The WAAMpeller was fabricated from a nickel aluminium bronze (NAB) alloy at RAMLAB, 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 CAD company Autodesk’s advanced manufacturing facility in Birmingham, UK.
Damen’s involvement in the project began in May 2016 as a result of one of its in-house student research programmes. “Three students from Delft University of Technology were investigating the potential of 3D printing for us. They brought us into contact with the other members of the consortium,” Kees Custers, project engineer in Damen’s research and development department, told Marine Propulsion. “What is unique about this group of five companies is that, while we have joint interests, we also have individual aims. This leads to a very productive and co-operative atmosphere in what is a very exciting project,” he said.
While 3D printing (or additive manufacturing, as it is more properly known) produces geometries that cannot be manufactured any other way, this prototype 3D-printed propeller still represented a steep learning curve of the understanding of material properties. “This is because 3D-printed materials are built up layer by layer,” said Mr Custers. “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,” he added.
Due to 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 with 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,” explained Mr Custers.
It can also be said that the 400 kg 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,” explained Mr Custers.
Yannick Eberhard, from Promarin’s R&D department, added that “the transformation from a semi-automatic to robotic processing is the solid foundation for even more complex and reliable future propeller designs."
“Material characterisation and mechanical testing have been an important part of this project,” says Wei Ya, a post-doctoral 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,” he explained.
Highlighting RAMLAB’s capacity to print objects with maximum dimensions of 7 m x 2 m x 2 m, Mr Ya said: “For large-scale 3D metal deposition, the WAAMpeller is really groundbreaking 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.”
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,” noted Mr Custers. “We are aiming to install this second one on to one of our tugs later this year.”
Damen invests considerable resources into its various research and development programmes. “Our aim is to build more effective, more cost-efficient and more environmentally friendly vessels,” commented Damen’s principal research engineer Don Hoogendoorn.
“The WAAMpeller project contributes to this goal. Not only does it mark an important advance in 3D printing, but also it has the potential to yield significant results in optimising future vessel designs. 3D printing technology brings with it an excellent opportunity to improve ship structures in terms of both performance and fuel consumption.”
New features added to HydroComp PropElements
HydroComp has added significant new features to HydroComp PropElements 2017
Launched in January this year, PropElements is the latest version of HydroComp’s tool for wake-adapted propeller design. It allows naval architects to become a meaningful participant in the design and analysis of these contemporary propellers at later design stages.
In wake-adapted propeller design, a custom propeller is optimally matched to the unique inflow properties of the vessel (its 'wake field'). PropElements is able to consider axial and tangential inflow properties, and ascertain optimised distributions of pitch and camber for prescribed foil characteristics. Of course, the propeller design process with PropElements takes into account blade strength, tip and hub loading, and cavitation. Its calculation pages include propeller, performance, and strength, with supplemental calculations such as for the creation of KT-KQ curves (see the sample screen shot.)
The foundation of PropElements is a unique distributed blade foil code, with empirical connections that allow analyses to be viscous and fully scalable. These corrections are made possible through HydroComp's experience in hybrid empirical-numerical hydrodynamics. PropElements supports standard nozzle styles, with optional support for contemporary high-efficiency nozzles and tunnel thrusters.
While built on the same analytical code-base as an earlier version of PropElements, the 2017 version is a novel program that tackles the component-level hydrodynamic needs of naval architects. The latest update offers a predictive tool that can handle custom and semi-custom propeller analysis, and allows naval architects (and propeller specialists) to investigate propeller iterations at later design stages. HydroComp PropElements is now able to evaluate a propeller or walk a design much closer to 3D CFD in a shorter time-frame and at reduced cost.
Key upgrades include a new interface using the HydroComp common GUI (as found in PropCad and NavCad). In addition, there is new high blade-loading curvature correction for low J accuracy, as well as prediction of induced volumetric flow rate.