3D printing Feature
historical restoration. “If you had a historic building, you could 3D print the mould from a 3D laser scan and take the plaster cast out of it. There’s already a company in the US that prints the moulds,” says Lee. Skanska’s Culling thinks it could be useful for external landscaping features — possibly because Skanska is experimenting in this area. Culling brings up the question of where
3D printing fits in to the sustainability argument. “So many projects these days are BREEAM or LEED-led. If you’re looking at the carbon implications of the actual construction process, what is the carbon footprint of 3D printing?” Looi’s response is that “it has to be more sustainable than shipping materials from China”. But Lee’s explanation is slightly more nuanced. “Any process that involves sintering a powder [with a UV laser] or cutting metal will involve high temperatures. It’s probably not any more energy efficient than moulding — although it depends on the temperature you need to work at. But a lot of the carbon comes down to sourcing the materials and transport, so the energy used might be less important than the transport carbon,” he agrees. “Or the energy in use,” interjects Carter. “That’s where 3D printing could be interesting — if it could print insulation.“
Rethink building design The group agrees that the future of 3D printing does not lie in retrofitting it to today’s methodologies, but in creating new construction typologies that exploit its potential. “If, in 10 years, 99% of buildings are designed the same way as today, then no I don’t think we’ll see a 3D printing revolution,” says Lee. “We need buildings designed around its capabilities. It allows you to do things that couldn’t have been done in the past, it needs engineers with the ability to do things anew, to come up with new forms.” Looi agrees, but points to the need for
extensive research and testing. “Clients will want guarantees. Until 3D printed components have been fully trialled, I don’t see anyone signing a collateral warranty.” But she also points out that if 3D printing does become a viable option in the future, it might usher in a different approach to construction, and therefore to contracts, liabilities and warranties. “It
26 | OCTOBER 2013 | CONSTRUCTION MANAGER
could be that the lifespan of buildings will be shorter. If a building or a component fails, you just print some more.” Overall the group is confident they are witnessing the awkward adolescence of a technology that will mature over time. Several times, members of the group advance a variation of the Moore’s Law argument — that computer processing power doubles every 18 months. If 3D printing is on the same technological path, we could be looking at a new method of design and manufacturing that could open up all kinds of new possibilities. “I have a dream of a future where we build a major project and if ever you need a spare part, you would just 3D print it directly from the BIM database,” says Lee. “But maybe it’s just a dream...” He’s right to be cautious, but the fact that 3D printed cladding components were last month installed in a mainstream City of London office project (see box, page 25) certainly brings the dream a step closer. CM
Researchers on Loughborough University’s Freeform Construction project are developing techniques to print concrete wall sections that incorporate voids to thread services
FDM or SLS?
There are two 3D printing techniques relevant to architecture and construction. iMakr sells entry-level printers based on fused deposition modelling (FDM), which allows objects to be made direct from 3D CAD files. The technique is probably what most people think of as 3D printing: a print head with a nozzle deposits filaments of plastic or other materials that are unwound from a coil. The nozzle is heated to melt the material, and its movements are controlled by software. The models at iMakr are printed in
ABS (acrylonitrile butadiene styrene), a plastic that is available in different proprietary formats that is often used to make car bumpers and also found in Lego. ABS components can be smoothed and sanded after printing and given additional coatings, such as paint or waterproofing. But as a pliable thermoplastic, ABS is prone to warping if it is cooled too quickly. Ceramics or metal powder mixed with
an epoxy binder can also be printed on an FDM printer, but would have to be fired in a kiln to achieve the same strength characteristics as the original. Another issue is that manufacturers’
printers are designed to print only the materials it produces. “There are compatibility problems — filaments and printers need to match. In the future, we will probably see norms and standards for 3D printing that allow more interchange,” iMakr’s Sylvain Preumont says. Another important limitation is that it is impossible to print above a void: if there’s an unsupported part in a design, the printer will automatically print “support”, often in another material, that then has to be discarded. George Lee’s print bureau, Lee 3D,
on the other hand, prints models using selective laser sintering (SLS), which is also a form of additive manufacturing. It involves putting layers of plastic powder on a machine bed, and using laser pulses to selectively fuse them into a solid. The shape is built up layer by layer:
after the laser completes one horizontal cross-section of the desired shape, the powder bed is lowered by one layer thickness, and a new layer of material is applied on top. Skanska’s experiment with 3D printed nylon cladding at the Bevis Marks project (see box, page 25) used an SLS machine. SLS can also be used with metal
powder, ceramic or glass. But as the technique is always based on powder, the resulting components are porous unless finished. Lee says the technology is still
maturing. “For construction, what you need is controllability, but with SLS [using plastic powder], to get the right standard you end up throwing away the sub standard prints, which can be up to 40% of what’s built. We need to get to a point
where it’s right every time.”
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