Will 3D printers construct your next house?

In a recent TEDx presentation, Dr. Behrokh Khoshnevis, a USC engineering professor, showed off a prototype 3D printer he says may one day construct buildings in 20 hours. In the presentation, the printer extrudes a special composite fiber concrete to build a six foot wall, layer by layer. A computer animation demonstrates what the entire process might look like, complete with full scale walls, plumbing, and electrical. Voilà! It’s a house, neat as you please.

Dr. Khoshnevis calls his process “contour crafting,” and the video has caused a bit of a stir online. But novel as it seems, at first glance, there isn’t actually anything new about the machine, conceptual animation, or that mindboggling 20 hour goal. Contour crafting hit the press—animation in tow—as early as 2003, while Dr. Khoshnevis has doggedly pursued automated construction for 18 years.

Here's the TEDx talk from Dr. Khoshnevis:

The professor first came up with the idea while repairing cracks in his house after the 1994 Northridge earthquake. He couldn’t help wondering why there wasn’t yet a better, easier way to do construction. Three years later, Dr. Khoshnevis and his graduate students got to work. Using his experience in rapid prototyping technologies, Dr. Khoshnevis’s first machines were capable of building small clay structures using a robotic nozzle, a trowel (to smooth surfaces), and a CAD program dicatating the design. Soon he realized the machine wasn’t restricted to clay, but could use construction materials, like concrete. So, why not construct entire buildings with the technology?

The answer, as it turns out, wasn’t all that simple. Although concrete has been very successfully used on grand scales—from mega-dams to skyscrapers—builders require moulds and forms to support the concrete as it sets. Though initially discouraged, the professor persevered. Overcoming the concrete problem took a year of research in concert with the German materials lab, Degussa. But their work paid off with a special form-free, composite fiber concrete capable of supporting itself during construction. Even more encouragingly, the viscous material did not clog the machine’s nozzle with sand and other particulates.

The new concrete formulation led to a significant round of contour crafting buzz in 2004 and 2005 when Dr. Khoshnevis’s machine automatically constructed a wall five feet long, three feet high, and six inches thick. Excited with the success, he dubbed the structure “the most historic wall since the Great Wall of China.” After 20,000 years, he said, “the process of constructing buildings is about to be revolutionized.” The custom crafting team aimed to complete their first house in less than a day by the end of 2005. Meanwhile, Dr. Khoshnevis optimistically predicted industry-wide use of the technology by 2020, at a cost of a few hundred thousand dollars per machine. By 2025, he believed contour crafting would be near ubiquitous in construction.

Considering how far 3D printing has come in the last decade, Dr. Khoshnevis’s unbridled optimism may seem warranted. (See here for a great synopsis.) Today’s 3D printers are capable of working with varied materials, including construction materials like plastic, wood, glass, steel, and, of course, now concrete. Further, 3D printing has already gone ultra small, making miniscule models of race cars and cathedrals. Why not big too? Certainly, beyond just the walls, it’s also important to get more intricate internal details right, like efficient placement of plumbing and electrical. But 3D printers have proven capable of following incredibly intricate computer plans—Neri Oxman’s beautifully impossible sculptures, for example. And as Dr. Khoshnevis likes to say, “The second hand on your watch was placed robotically on a tiny shaft. So having segments of tubing robotically inserted, put atop one another, and welded together as the wall goes up is really a no-brainer.”

The technology’s benefits, on paper, seem to similarly make its adoption a no-brainer. In his TEDx presentation, Dr. Khoshnevis notes that like most additive technologies, contour crafting cuts waste by using only the materials needed. The end product is as customizable as a computer plan. Replacing onsite construction workers with a single machine greatly reduces labor costs and accidents. The dramatically shorter and more consistent building period reduces financing costs, like risk-related interest on loans and opportunity cost. Structurally stronger (and attractive) curvilinear geometries are as easily printed as the currently more common rectilinear forms. Put simply, contour crafting could be safer, simpler, more flexible, less wasteful, and above all cheaper than traditional construction.

There must be a market for a machine that does all that, right? Dr. Khoshnevis believes it can provide housing for victims of natural disasters as well as the billion or so humans living in sub-standard housing worldwide. Eventually, it could construct apartment buildings, high end custom homes, even moon dwellings.

To be sure, contour crafting was buzz-worthy back in 2005 and almost seemed inevitable—not unlike today. As Dr. Khoshnevis says, “If you can build a wall you can build house.” But seven years after the first blush of excitement and halfway to that 2020 benchmark, the team is stuck building walls but six feet high. Meanwhile, the rest of the machine’s capabilities—plumbing and electrical installation—remain in the conceptual stages. So, what’s the hold up? Perhaps Dr. Khoshnevis’s own words, in 2003, best sum up the challenge, “We are talking about much larger machines, much greater volumes of material, and working outdoors in less controllable environments.”

There are certain questions that can only be answered in full-scale testing of the process. The nozzle may remain free of debris after constructing a single wall, but what about after a whole house—or ten houses? How much more costly is the special composite fiber concrete than conventional concrete? Is it easy to make the special concrete locally, or will it need to be shipped in at great expense? Can the design be changed mid-project? With traditional construction techniques, it's easy to change course quickly on the design. But such changes may be more difficult using a 3D printer.

Dr. Khoshnevis believes his “technology is like a rock rolled to the top of a cliff, one little push, and the idea will roll along on its own.” But these days, his forecasts are a touch more modest. The machine could go full-scale in two years, he says. What will it take to really get rolling? He has had modest financial backing from the National Science Foundation and Office of Naval Research, early on, and Caterpillar Inc. and NASA more recently. But perhaps ultimately the needed nudge can only come in the form of a well run start-up and a big infusion of private capital. Why neither has materialized to date is a meaningful question. One whose frustratingly circular answer may be, “If you build it, we will come.” Until that happens, those of us awaiting our very own custom house hot off the printer are bound to be disappointed. Contour crafting firmly remains a promising but unproven technology.

[Media: TED]

[Source: Contour Crafting]

Jason is managing editor of Singularity Hub. He cut his teeth doing research and writing about finance and economics before moving on to science, technology, and the future. He is curious about pretty much everything, and sad he'll only ever know a tiny fraction of it all.