Skanska claims first with 3D printed cladding
A Skanska-built office project in the City of London has achieved an industry first by taking 3D printing out of the research labs and into a live project environment.
The 6 Bevis Marks project boasts 3D printed cladding “shrouds” for the top section of tree-like steel columns supporting an ETFE roof on the building’s roof terrace.
The shrouds were delivered to site last week and installed by Skanska this week.
“We’re very excited by it – it’s the first time the company has used the technique,” says Skanska project manager and innovation champion Jonathan Inman. “But we’re currently talking to other clients about other opportunities for 3D printing.”
Skanska’s head of innovation Sam Stacey added: “It’s something we are very interested in, we will look for opportunities and respond vigorously as they emerge.”
At Bevis Marks, 3D printing proved the ideal solution to a tricky technical problem. Eight different complex interfaces between roof and column were originally envisaged as cast steel nodes, but Skanska foresaw considerable expense and difficulty. Alternative welded or spliced steel plate options were considered, but did not meet architect Fletcher Priest’s aesthetic standards.
As the ETFE roof package was the responsibility of specialist company Vector Foiltec, its consultant Adrian Priestman sought a solution beyond the industry’s current skill set.
The cladding “shrouds” (below) support an ETFE roof on the roof terrace
In November last year, Priestman approached High Wycombe-based Quickparts, formerly known as CRDM, which “prints” bespoke components in low-to-medium volume for the aerospace, defence and medical devices industries.
Simon Hammond, regional sales manager, says that Quickparts has been quietly innovating while others have been noisily discussing: “What people see in the news or on the BBC represents the consumer end of 3D printing, the machines you can buy for the home or office. But we’re a commercial bureau, we print parts for human bodies or parts of aeroplanes or Formula One, and they’re not prototypes – people are adopting 3D printing because of the advantages it brings.
“3D printing is not here to replace traditional manufacturing, but it does go through the ceiling of what you can do cost effectively. It comes into its own when a low volume production run [using conventional manufacturing] is prohibitively expensive.”
Bevis Marks was an ideal candidate for 3D printing, due to the complexity and lack of repetition in the design. “With eight different iterations, other types of manufacturing would need eight different moulds, but we produced eight unique [cladding] shrouds, according to CAD specifications.”
Quickparts used a Selective Laser Sintering machine that fuses layers of powdered Nylon PA 12 to build up the complex shapes. “We took the CAD file from the architect, then ‘sliced’ it into 0.1mm layers. The laser operates above a movable platform, so it traces one slice of the layer by putting enough heat on the nylon to melt it. Then the platform moves down by 0.1mm, you put on more powder and built it up layer by layer,” says Hammond.
The eight cladding nodes, termed “shrouds”, were printed in different sections – a process that took around three weeks in total – then jointed. Finally, the 600mm wide, 800mm high nylon shrouds were finished and painted to resemble steel.
But as the product did not carry any conventional warranties, Skanska and the design and client teams naturally had reservations. “The material had not previously been used in an external environment, we needed a lifespan of 10-20 years, and there were also issues about the joints,” says Skanska’s Inman.
But Quickparts and Vector Foiltec commissioned accelerated exposure testing to simulate the rain, sunlight and heat in the open-ended atrium, and the shrouds performed well. Vector Foiltec was then confident enough to cover the shrouds in its overall roof warranty.
“The architects were quite concerned about it, but they realised the technology is pretty well tested in other industries, and Quickparts were dealing with the testing in an appropriate way,” says Inman.
Hammond says Quickparts is optimistic that Bevis Marks could open the door to further work in construction, albeit in non-structural applications. “We’ve got the confidence now because the material has been confirmed as OK – we have the certification and evidence. We understand that this is a big deal for construction clients.” As well as nylon, Quickparts can also print in a range of plastics and metals, including stainless steel 316 and cobalt chrome.
And Hammond also adds that SLS “ticks a lot of green boxes”. “With reductive manufacturing, you can lose up to 90% of the material, but we only use the amount of material that you need.”