Arup Uses 3D Printing to Create Tensegrity-Inspired Structural Bridge Parts

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Many people have heard of 3D printing with plastic or resin. The basic process extrudes a heated plastic in thin layers to gradually create a three-dimensional object.

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Until recently, though, only a few had heard of printing with metal, a different process that uses a laser to combine metal powder into a shape. Now, companies in the automotive and aerospace industry are utilizing this new type of production to create more complex and lighter parts.

By using additive manufacturing, complex pieces can be created far more efficiently.

By using additive manufacturing, complex pieces can be created far more efficiently. Image courtesy of Arup.

The architecture, engineering and construction industries, however, have not yet begun to use 3D printing for any of the structural elements of buildings, roads or bridges. When Arup, a global engineering firm, was tasked with creating components for a bridge that didn’t follow conventional design, they decided to put additive manufacturing (AM) to the test as an internal research project. Arup wanted to see how a printed part could hold up to structural standards as the elements being designed had to be load-bearing bridge connections as well as lighted fixtures.

The look of the structural nodes Arup designed was inspired by the Kurilpa Bridge project many of the engineers previously worked on. Kurilpa is a pedestrian bridge in Australia based on principles of tensegrity – a balance between compressive and tensile members. As a result, Kurilpa has a more natural look than most bridges.

For the research project, Arup’s engineers came up with a complex design that looks like roots. Extra struts were added to the part to support it during printing. The struts allowed for a hollow design that reduced the weight of the node and was more aesthetically pleasing than a traditionally machined node.

The team had little to no prior knowledge of 3D printing of parts before they undertook the research project, said Arup Senior Engineer Salomé Giljaard, who oversaw it. They had to learn how to adapt a design to the new constraints of the printers.

Many people believe the 3D printer heralds a new age in manufacturing. They think that companies will turn to 3D printing to more efficiently make all products. Giljaard, however, said “We do not think (AM) is a destructive technique; that everything will be printed in a couple of years and that it will take over all other traditional production techniques.”

Arup does hope that AM will be added to a long list of production techniques currently used by engineers, as it allows for new degrees of design freedom.

A 3D printer can produce complex shapes in the same amount of time and with the same amount of ease as it can create simple shapes. The new parts can be designed to be lighter than previous production techniques allowed. The biggest limitation to 3D printing is imagination, Giljaard said.

At the moment, a kilogram of a powdered metal is, not surprisingly, more costly than a kilogram of the same metal in solid form. Looking into the future, Giljaard thinks the materials industry will grow, both the suppliers of the raw metal and the companies that create the raw powder.

A traditionally produced steel node is, at the moment, still cheaper to produce but it's also an aesthetic compromise and prices have been coming down for 3D printing for the last decade.

A traditionally produced steel node is, at the moment, still cheaper to produce, but it’s also an aesthetic compromise and prices have been coming down for 3D printing for the last decade. Image courtesy of Arup.

As the market starts opening up to more developers and producers, the price of metal powders will come down, allowing for AM to grow.

When asked which metals could be used, she told MetalMiner that, “In theory any material that can be made into a powder can be used.”

Giljaard also said that advancement will be an exchange, in that companies will begin using materials that no one in the industry had previously thought to use, at the same time stopping the use of older production techniques. At present, raw material is NOT the most costly part of AM. The main expense comes from the printers, themselves, and the time it takes to print the parts. Hopefully, these costs will drop as well as 3D printing grows.

The component that Arup created was made to help test out AM in architecture and engineering. Arup is going to continue to develop the parts to take it as far as they can. They are already planning on incorporating 3D printing into future projects in real-world applications. Giljaard said, “We have had a lot of responses to our research so far and our work and we hope people are really inspired by it.”

Finn Roberts is an editorial intern here at MetalMiner. He reported this story while putting up with all of us here at the home office this Summer. We’re sorry about all the puns.

Comment (1)

  1. Great article, Finn! I can imagine many applications for AM with metal, such as furniture, art, tools, and many more.

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