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Last June, Beijing based construction outfit HuaShang Tengda made world headlines when it announced that it had printed a two-storey, 400 square metre home in 45 days.

Whilst cases of apartments being printed in days had previously been reported, this according to reports was the first time a complete home had been done in one go without any need to be manually pieced together. Excited media ran headlines about the printing of machines which sit on site and churn out entire houses.

Welcome to the world of 3D printing, which involves the creation of a printed material or object using additive processes by laying down successive layers of raw material until the end product is completed. A number of technologies exist to do this in construction – or more commonly, to make the materials which go into modern construction.

The approach pioneered by the Contour Crafting group and adopted by HuaShang Tengda involves ‘concrete deposition’ in which concrete is mixed through a batching or mixing plant before being pumped onto the machine and printed layer by layer.

Another technique known as ‘D-shape’ relies on the 3D printing to bond sand or other materials together layer by layer to create an object, before removing the sand and revealing the object. Branch technology is different again and involves 3D printing of plastic type of materials, while additive welding technology known as MX3D focuses on the printing of metals.

Whilst the above techniques involve the 3D printing of the materials themselves, a further interesting approach involves printing the moulds which shape the materials. Toward this end, Laing O’Rourke have pioneered a FreeFAB Wax technology which involves 3D printing and milling to create wax moulds into which precast concrete is poured or sprayed before being cured and placed into a hot bath (which melts the wax, leaving concrete forms ready to go). What is 3D printed is not in fact the concrete but rather the moulds into which the concrete is poured. The advantage of this approach, Laing O’Rourke believes, is that it facilitates high strength and precision components which do not require any finishing by hand and enable the recycling of all mould materials.

So will machines going on site and churning out homes in days or weeks become commonplace down under anytime soon?

Most likely not, says Dr James Gardiner, lead of Construction 3D Printing Innovation at Laing O’Rourke. Gardiner says many of the claims about houses being printed in days need to be put into perspective. Whilst you might see the superstructure being printed in that time, he says there is also weeks or months of work which go into preparing the site and the foundations, assembling the machine and performing subsequent finishing work such as installation of bathrooms and services after the superstructure is finished.

“I’m certainly very aware of claims about houses being printed in a day which have been talked about since 2006,” Gardiner said. “Often these claims are very thin in what they are actually talking about. If you properly compared these claims with all of the phases of traditional construction, I think that they tend to leave a lot out.”

According to Gardiner, a common misconception surrounds the notion of printing taking place on the site itself. Instead, he says 3D printing is more likely to be performed off-site in a factory, with concrete panels and other parts subsequently being transported and assembled on site.

There are several reasons for this. In order to 3D print a house, the machine needs to either be larger than the house itself or have the necessary reach needed to build a house (such as a crane). Printing on site requires the machines to be transported, assembled, disassembled, taken to the next site and then reassembled each and every time – a time-consuming and expensive process which creates wear and tear on the equipment.

The process is also susceptible to wind as well as changes in temperature and humidity and is therefore difficult outside of a controlled environment. As it stands, construction 3D printing on its own is less accurate compared with traditional building processes and requires secondary finishing in order to bring it up to standard – a task more easily performed in a controlled factory environment.

Furthermore, offsite printing can utilise equipment which is too heavy for transportation (such as precision gantries) and make better use of labour and equipment (because work can be easily accessed, labour can be shared across projects, and assembly lines with multiple machines can be used). In addition, when materials are printed off-site, critical finishing tasks such as milling, sand blasting and painting can be performed in a staged production style arrangement.

A second myth, Gardiner says, revolves around notions of 3D printing costing around 50 per cent less than traditional materials. Whilst he acknowledges that construction 3D printing can be very cost effective, he says many of these claims take into consideration only the costs associated with 3D printing and compare these to traditional construction, which reflects not only the production of the structure but also include site preparation, services fitout, finishing, temporary works, labour, certification and other costs.

Nevertheless, Gardiner says construction 3D printing offers advantages in terms of design flexibility. With 3D printing, the geometry is essentially free and the printer does not care whether or not you are printing five of the same items or five completely different items. Therefore, building in this way enables greater flexibility in terms of building form compared with what would be the case in using conventional methods.

This might allow, for instance, the optimisation of walls so that material is used only where it is required. Rather than having brick walls, for example, built with the same strength throughout, you could optimise the materials so that the wall is stronger where more strength is required (in and around doors, windows and corners for example) and subtract material elsewhere where less strength is needed.

You can also have more interesting arrangements such as houses which are shaped like organic rocks to better fit in with the landscape surrounding it, Gardiner said. That structure, he said, could in turn be designed to respond to sun angles and thermal loading.

Associate professor M. Hank Haeusler, discipline director of Computational Design at the University of New South Wales, said the notion of 3D printing being commonplace within 10 years is reasonably plausible. Pointing to the more rapid than expected proliferation of smart phones over the past decade, he said a decade is a long time in technology terms.

Courtesy of some of the aforementioned issues, however, Haeusler agrees that the primary use for 3D printing will revolve around digital fabrication offsite. He says much of the benefit revolves around the ability to synchronise scheduling in a controlled environment to ensure that parts are ready when needed. This will enable, for example, large machinery such as power generators intended to go inside the building to be delivered exactly when needed without hold ups associated with delays and a need to wait for equipment.

Peter Bowtell, a structural engineer and principle at Arup who heads up Arup University, expresses broadly similar sentiments. Whilst acknowledging the advancements which have been achieved within the 3D printing sphere over the past decade, Bowtell cautions about a ‘hype cycle’ whereby initial excitement surrounding the possibilities on offer is followed by a trough of disappointment before more pragmatic ways in which 3D printing can be applied within the building process are adopted.

As with Gardiner and Hausler, Bowtell says the real area of excitement revolves around offsite fabrication. Overseas and especially in Europe, he says, the delivery of housing is shifting away from traditional construction processes and toward manufacturing and on-site assembly. Where 3D printing helps, he says, is in areas such as the ability to produce moulds like the wax moulds through the Laing O’Rourke system (FreeFAB wax) which can then be used to mass-produce complex (one off) elements.

In terms of how this will impact workers and trades, Hausler says general moves toward offsite fabrication and onsite technologies such as robots will see many largely manual and routine tasks replaced by machines. Bowtell, meanwhile, acknowledges that digital fabrication will reduce onsite labour requirements but adds that this will be at least partly offset by Australia needing to build more going forward. Moreover, he says Australia needs to look at how people can be trained and equipped with skills in digital manufacturing.

Despite his aforementioned caution, Bowtell says it is important to adopt a positive approach.

“I do think it is important to keep an open mind about this,” Bowtell said. “We have seen major advances in other applications of 3D printing and the possibilities over the past five to six years. I think we are going to see it increase in terms of its application.

"All I would say is that it is important not to leave a sense of scepticism. In my mind, it’s a sense of opportunity that 3D production provides. It is important to explore the opportunity. Innovative companies that focus on this will create disruptive change to our industry.

“I do think the five to 10-year hype cycle of a whole house printed is exactly that. (However,) I do think that we will find something more pragmatic but really exciting at the same time.”

 
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