Generative design is a computational design approach that mimics the evolutionary designs of nature. Designers input their design goals and parameters into generative design software, which uses cloud computing to explore and test all possible solutions and generating alternatives to aspects that don’t work. The designer then chooses the solution that works best for the project. Engineering firm Arup has been using generative design to create lightweight, complex structures, and a recent project has been getting a lot of attention.

Arup is known for the Sydney Opera House as well as several other landmarks around the world, and recently they were called upon to design three large tensegrity structures for a shopping street in the Hague. The structures, which were integrated with lighting, were called “urban chandeliers” and together featured 1,600 metal nodes that connected the cables to the struts. Because of the irregular shape of the structures, most of the nodes were differently shaped.

Not only did Arup use generative design for the project, they also implemented something else they’ve been incorporating into their work: 3D printing. While 3D printing has been around for a while in construction, it’s mostly been 3D printed concrete; 3D printed metal construction elements are still new, and while the technology enabled Arup to create individual, differently designed elements, it wasn’t perfect, as it turned out.

Arup ran into a few issues using 3D printing: overall, 3D printer build chambers are still relatively small, and printing 1,600 pieces was a slow process. The cost was also high, and regulation was an issue; construction safety standards still do not allow for 3D printed metal parts in critical positions. So Arup began looking at ways that they could still use the benefits of 3D printing but mitigate some of the drawbacks.

They worked with 3Dealise, a service bureau that designs and engineers products for clients using techniques such as 3D printing and scanning, reverse engineering, and rapid manufacturing. 3Dealise, among their other equipment, has a gigantic sand 3D printer, the S-Max from ExOne, and they used it to 3D print a mold for one of the nodes. They then worked with a foundry to produce a casting, in a hybrid approach that combined the benefits of 3D printing, such as design freedom, accuracy and short lead time, with those of traditional manufacturing, such as the ability to produce large items and regulatory pre-approval.

The process used by 3Dealise and Arup demonstrated several benefits: the hybrid approach was both technically and economically feasible, and the generative design approach achieved a weight reduction of 75% compared to traditional design methods. Compared to metal 3D printing, lead time was faster and cost was lower, and the process was more sustainable, as less material was used.

“An interesting shift is taking place; whereas the focus initially has been on printing final products, 3D-printing is being applied in an earlier phase in the production process,” said Salomé Galjaard, Senior Designer at Arup. “The aim is to make the most of the freedom-of-form opportunities of 3D-printing without the limitations which are now still considered with production.”

The project represented a challenge for 3Dealise as well; because of the complexity of the node’s generative design, conventional methods of sand mold design would not work, so the company invented an entirely new approach to sand mold design. This meant that process changes had to be developed and implemented across every stage of production.

The 3D printed sand mold and cast metal node. [Image: Davidfotografie]

“This project highlights two key points: First, this hybrid 3D printing approach is feasible both technically and economically for production of generative designs in the building industry. And there are no regulatory hurdles, so there is really nothing stopping the application on a large scale in the sector,” said Roland Stapper, CEO of 3Dealise.

“Second, this technology has a huge cost advantage over direct 3D metal printing, particularly for larger products. 3D printing is often associated with relatively small products, but the benefits of 3D printing are also cost-effectively available for a whole class of larger and heavier metal products in critical load-bearing positions.”

A copy of the node that 3Dealise produced for Arup will be on display at the TCT Show, which is taking place in Birmingham next week from September 26 to 28. You can stop by and see it at Booth G25.

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[Images provided by 3Dealise unless otherwise noted]

 

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