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Smart materials | 3D printing

Whether it is developing technology for 3D printing houses on earth, or sintering landing pads on Mars, an optimistic Behrokh Khoshnevis has only the good of humanity in mind.

It was 22 years ago that Khoshnevis’ idea for large scale 3D printing emerged.

“Typically sub-millimetre layers were used [in 3D printing], to build objects. If you increase layer thickness you lose design specificity, so therefore everybody kept the layer thickness low. I knew the only way to speed up this process was to increase layer thickness,” says Khoshnevis, who, among other academic duties holds the post of professor of civil and environmental engineering at the University of Southern California.

He called it contour crafting, and it was originally designed to create moulds for industrial manufacturing.

Cc curve house

Cc curve house

Artists impression of 3D printed house

But around 2003 the University of Southern California professor began experimenting with construction materials, such as gypsum and woodchip, and finally fell upon 3D printing for concrete.

“Several years after that, nobody was doing anything in the field and not much serious interest was shown by anybody.”

Exactly when this changed is hard to pin down.

It could have something to do with headline-grabbing 3D builds popping up around the world. Multi-storey buildings appeared in China in early 2015, with one company claiming to build 10 houses in a day. Khoshnevis has said the Chinese company responsible is infringing on his patents, but he is now further ahead in his technology to be bothered pursuing legal action. But the Chinese company involved has now reportedly signed deals in recent months for housing projects in Egypt and Saudi Arabia.

Khoshnevis cropped

Khoshnevis cropped

Khoshnevis: 3D printint pioneer

In May 2016 the “world’s first functional printed office building” with 250m2 of floorspace was unveiled in Dubai. A printer produced the 36m long, 6m tall and 12m wide modular building in 17 days and it was assembled in two. The Dubai Government boasted that labour costs for the project were 50% lower than those incurred using traditional  construction methods.

Khoshnevis says much of this current hype is unjustified.

“There was hype about personal 3D printers, and they thought everybody would have one in their homes, printing day-to-day objects. That proved to be wrong. People don’t have the interest, there’s not too many useful objects you can make at home, other than toys, and apparently there’s not many people interested in building their own toys.”

I knew the only way to speed up this process was to increase layer thickness

But the 3D printing process’ undoubted strength is time saved. Khoshnevis says an entire 250m2 house ‘“shell” has been done within 24 hours.

And in terms of strength or maintenance, Khoshnevis says the difference is negligible.

“The main strength in a building comes from the joints and the engineering design – the process has a smaller impact.”

Extrusion or powder

Three-dimensional printing occurs in one of two ways: via extrusion or powder. With the powder method, a layer of powder is laid down, followed by a liquid binding material. The process is repeated, with each layer adhering to the last. Extrudors pump the mixed wet materials directly onto to the semi-dried layer. Khoshnevis says the powder method was tried using concrete, but the extrusion method was more streamlined.

When questioned about how the interlayers adhere, Khoshnevis counters with another question: why not ask this question of bricks?

“With bricks you have dry material used with wet mortar, but nobody seems to question that. At least with 3D printing you have wet mortar on semi-wet mortar.

“When we do try to break [the structures], they typically break from any random location, not the interface.”

So the main hurdle is not the material, but economics. Khoshnevis is currently focusing on commercialising a 3D printing company called Contour Crafting Inc “We’ll be active in 2017,” he says.

But enticing construction companies to step into a robotic future is proving difficult. For example, Khoshnevis says: if the building process were ever fully automated, house prices would be one-fifth what they are today.

But there are practical obstacles to the widespread adoption of 3D printing in construction.

Everybody should be able to do something creative, not limited to repetitive tasks

“Everybody wants somebody else to take it through the approval process. And then nobody wants to pay out of their own pocket. In certain cases the labour unions also become a barrier.”

On the broader topic of automation, Khoshnevis says bricklayers do not need to fear job losses overnight. But if machines can build better, then they probably should be concerned in the longer term.

“When there has been a new technology that automates, takes over humans, typically the consequence is that there are changes in the economy to provide new opportunities,” Khoshnevis says.

Driving economic change

“Take the case of US agriculture. In the early 1900s, 51% of Americans were farmers, today less than 1.5% are farmers. So what happened? In 1900 we didn’t have GPS, nanotechnology or genetic modification.

“The kinds of jobs in the future are very hard to predict, the same way that people 150 years ago we could never imagine that millions of people would be flying in metallic machines in the sky.”

Alleviating poverty

Khoshnevis suggests there are 2bn people across the world living in slums that could benefit from 3D printing. He predicts anything that has to do with physical work is going to be automated by robotics.

One of Khoshnevis’ creative pursuits has been to convert his 3D printer technology to interplanetary colonisation.

Selective Separation Sintering (SSS) was demonstrated using high melting-point ceramics such as magnesium oxide (readily available on the moon and Mars) and ordinary regolith (planetary soil) to produce tiles that could withstand the heat and pressure of exhaust plumes of landing spacecraft.

“Without taking material from earth we are able to build using a reasonably good process,” he says.

Building in outer space

There has been a slew of NASA prizes for Khoshnevis’ ground-breaking work. Rather than a side-project it is the result of his heartfelt and humble passion – to ensure the future of humanity. Like other tech-visionaries in California, he believes humans are destined to live on more than one planet.

“I take it very seriously, it’s very close to my heart because I really think the future of humanity is in space. This planet is too small and vulnerable, and humanity deserves more than just one planet. A galactic civilisation and finally a universal civilisation – I think that’s what humanity should have in mind.”

“Compared to generations before us we’ve made amazing strides, huge progress, but this is just the beginning.”

Readers' comments (1)

  • I have always had a keen interest in new developments in3D-printing construction, especially in the States. However, it was a great disappointment reading about Dr. Khoshnevis' decision not to pursue a legal action against the Chinese company over the infringement of his patent. In layman's terms, it is a robbery which would have not been tolerated by the Chinese had the situation been reversed. Wishing Dr. Khoshnevis great success in his future research and even stronger will in protecting his rights

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