Building for the Future
It can take anywhere from six weeks to six months to build a 2,800-square-foot,
two-story house in the U.S., mostly because human beings do all the
work. Within the next five years, chances are that 3D printing (also
known by the less catchy but more inclusive term additive manufacturing)
will have become so advanced that we will be able to upload design
specifications to a massive robot, press print, and watch as it spits
out a concrete house in less than a day. Plenty of humans will be there,
but just to ogle.
Minimizing the time and cost that goes into creating shelters will
enable aid workers to address the needs of people in desperate
situations. This, at least, is what Behrokh Khoshnevis, a professor of engineering and director of the Center for Rapid Automated Fabrication Technologies, or CRAFT, at the University of Southern California, hopes will come of his inventions.
“Initially it will be most beneficial to developing countries to
eradicate their slums. Next is emergency shelter construction where war
and natural disaster uproots thousands of people,” says Khoshnevis.
“[It] can build much cheaper and much faster and can produce dignified
housing rather than tents and boxes.”
Khoshnevis says his system could be ready two years from now, but it
may end up on the moon before we see it in Haiti or Somalia. In late
November, NASA awarded a grant as part of the NASA Innovative Advanced Concepts (NIAC) to Khoshnevis and his collaborators as a possible way to build lunar structures. The team’s next step is to test the process at the Desert Research and Technology Studies (D-RATS) facility in Arizona.
Contour Crafting
Khoshnevis calls his technique “Contour Crafting” and it operates on roughly the same principle as consumer 3D printers like MakerBot’s Thing-O-Matic.
His robot pours out a trail of viscous concrete while tracing along the
footprint of a wall. As the nozzle sweeps back and forth, the layers
rapidly build, with the lower ones hardening enough to support the
increasing weight. Its speed puts construction workers to shame.
“We are talking about a technology that can build a square foot of
wall in less than 20 seconds,” Khoshnevis says. At that rate, Contour
Crafting can put together a whole room in just an hour.
It took a while to figure out how to make a printer that could build large objects at that speed. Most 3D printers
— those that make shapes using plastics — build in tiny layers, often
only .01 mm thick. The number of layers determines the resolution of the
object. Just like the pixels in a digital camera, and the more you
have, the more accurate the product will be. But when Khoshnevis tried
building from such thin layers, the process took too long to be useful.
Eventually, he found that he could build with much bigger layers,
over an inch thick, if he used a tool to smooth out the concrete as it
flowed from the nozzle. Ultimately, he attached two swiveling trowels
that let him remold the concrete into any angle.
Other robotic fixtures could be added to the printer, giving it the
capability to install plumbing and electrical wiring. A gripper would
place support beams and lay out a layer of metal over the top of the
walls to create a base for the ceiling and roof.
Printing a cube or an octopus
Size is now the only thing holding back the technology. “We have a
machine that can build a structure about 23 feet long, about 7 feet high
and about 15 feet wide at this point,” says Khoshnevis.
He estimates that a full-scale printer would break down into three
pieces and be small enough to fit onto a flatbed truck. All construction
would happen on site.
First, a designer would bring a digital blueprint for the house on a
thumb drive and plug it into the printer while workers loaded it with
concrete. Once the printer was activated, humans would play a supporting
role, laying out supplies for the robotic gripper arm and preparing
fresh batches of concrete. Humans would also install the windows and
doors, since the task is so easy it’s not worth automating, Khoshnevis
previously said.
Not only will it be faster, 3D printing could enable architects to design in completely new ways.
“There are definitely interesting implications,” says Sean Bailey,
an architect and artist in New York City. “Whereas traditional
fabrication techniques require additional resources as complexity
increases, 3D printers are not bound to this logic.” With a 3D printer,
it takes the same amount of time and money to turn a glob of concrete
into a cube as it does to turn it into an octopus, says Bailey.
As masonry has become more of a specialized, and therefore expensive,
skill, curvy architecture has become more difficult to produce. 3D
printing could bring back some of these shapes.
“There are numerous shapes that you can make with Contour Crafting
that cannot be made by conventional construction, such as doubly curved
surfaces which would be extremely cost prohibitive to build by current
methods,” says Khoshnevis.
