Arup pioneers 3D printed steel nodes
Arup has demonstrated how a form of 3D printing technique called additive manufacturing can be used to produce complex steel connections more efficiently.
The structural engineer collaborated with design software company WithinLab, 3D printing specialist CRDM/3D Systems and manufacturer EOS on a project to create 1,200 intricate steel “nodes” for a proposed street lighting scheme in the Netherlands.
The nodes form part a lightweight steel structure of angled struts, tension cables and lighting attached to the sides of buildings along a main street.
The complexity of forces at work meant that each node had to have a unique geometry and under the original design they would have been cut and welded individually by hand. However, Arup’s research showed that by designing the nodes for production using additive manufacturing techniques they could be formed faster and to higher quality standards.
The project is currently on hold, but Arup decided to progress the 3D printing technique to prototype phase using its own funding.
Conventional (left) and futuristic 3D printed steel nodes
“We had developed a detailed design for a street lighting project but it was put on hold, so we used the opportunity to investigate the efficiencies 3D printing could bring,” said Salome Galjaard, senior designer at Arup. “The 1,200 parts had to be very similar in design but subtly different and cutting and welding them by hand would have been expensive and had a greater potential to introduce mistakes. By using additive manufacturing we showed how we can create lots of complex individually designed pieces far more efficiently.
“This has tremendous implications for reducing costs and cutting waste. But most importantly, this approach potentially enables a very sophisticated design, without the need to simplify the design in a later stage to lower costs,” she added.
After initially examining literature on additive manufacturing used in aviation and automotive industries, Arup worked with its partners to design nodes made from tough maraging steel, which would provide the required strength whilst being simpler than stainless steel for manufacturer EOS to source.
“It was interesting during our early research over a year ago, several 3D printing companies said they never get any requests to work with the building industry, even though they were very open to the idea of using different materials for production, they just needed to hear from us about the specifics of the materials we want,” said Galjaard.
Designing for this innovative production technique also meant reassessing approaches to engineering design software, effectively starting from scratch to enable it to work.
“The 3D drawing software the construction industry currently uses is focused on traditional production techniques, such as extruding and rotating. 3D printing requires a very different method of thinking and the software’s focus on conventional approaches to production were limiting the flexibility and the many possibilities of additive manufacturing,” said Galjaard.
A typical design process would start by developing a form for a component based on the forces it has to handle, known as topology optimisation, followed by a process of optimising it for production by introducing constraints to the design to make it easier or cheaper to produce.
But here, Arup found it easier to implement these two processes simultaneously when designing for additive manufacturing. The firm is continuing its research and hopes soon to announce a trial on a small-scale live project.
“The technology has some way to go and we’re not ready to apply it to all of our projects, but these initial results are very promising,” concluded Galjaard.