3-D PRINTING A BUILDING
MIT group sees its robot as a revolutionary construction tool
future of construction just got a little bit closer. Researchers at MIT have created a mobile robot that can 3-D print a building-size structure in a matter of hours — a technology that could be used in disaster zones, on inhospitable planets or even in our proverbial backyards.
Though the platform described in the journal Science Robotics is still in early stages, it could offer a revolutionary tool for the construction industry and inspire more architects to rethink the relationship of buildings to people and the environment.
Current construction practices typically involve bricklaying, wood framing and concrete casting — technologies that have been around for decades in some cases, and centuries in others. Homes and office buildings are often built in the same boxy, cookiecutter-like templates, even though the environment from one area to another may change dramatically.
“The architecture, engineering, and construction sector tends to be riskaverse: Most project fabrication data nowadays have been digitally produced, but the manufacturing and construction processes are mostly done with manual methods and conventional materials adopted a century ago,” Imperial College London researcher GuangZhong Yang, the journal’s editor, wrote in an editorial on the paper.
In recent years, scientists and engineers have begun to explore the idea that buildings could instead be built through additive manufacturing — that is, 3-D printing. A home could be customized to its local environment, it could use building resources more efficiently and it could deploy materials in more sophisticated ways.
“Right now, the way we manufacture things is we go to the mine, we dig out minerals and materials, we ship them to a factory, the factory makes a bunch of mass-made parts, usually out of a single material, and then they’re assembled — screwed together, glued together and shipped back to consumers,” said lead author Steven Keating, a mechanical engineer who did the research as a graduate student under Neri Oxman’s group at the Massachusetts Institute of Technology.
But the group’s many projects, he added, revolved around this question: How do we actually fabricate in a way that is more consistent with how biology works?
Keating pointed to the tree as one example in nature. Trees can self-repair, operate with self-suffiThe ciency, produce buildingsize structures with locally sourced materials and adapt to their environment.
“These are the kinds of principles that we’ve looked at for a lot of the projects in the group,” he said.
While several groups around the world have been working on large-scale 3-D printing techniques, there have been challenges in this process, Keating said.
“A lot of other research projects that are looking at digital construction often don’t create something of an architectural scale — and if they do, they’re not using a process that could be easily integrated into a construction site,” Keating said. “They’re not using materials or a process that can be easily code-certified. And what we wanted to make sure could happen is we could actually break into the construction industry, because it’s a very slow and conservative industry.”
Keating and his colleagues’ robot, called the Digital Construction Platform, looks to address those issues. It features hydraulic and electric robotic arms and can be loaded with all kinds of sensors to measure its environment, including lasers and a radiationdetecting Geiger counter.
In less than 13.5 hours, the robot was able to zip round and round, printing a 14.6-meter-wide, 3.7-metertall open dome structure out of a foam used as insulated formwork.
Strange as it looks, this formwork could be filled with concrete. Since this is essentially what already happens in traditional construction, this 3-D printing process could be integrated into current construction techniques. (In both the traditional and 3-D-printed scenarios, the formwork ends up as the building’s insulation.)
This process has a number of advantages, many of which enable the robot to design and build more in the way that living systems in nature do, Keating said. Three-dimensional printing uses fewer materials more efficiently. It can also create useful gradients, such as reducing wall thickness from the bottom of a wall toward the top. (Nature does this too: Think of a tree’s trunk at the base versus near the top, or the way a squid beak goes from hard at the tip to soft at the base.)
This process can create and work with curves, which are usually more costly for traditional building methods. The formwork also cures so quickly (within about 30 seconds) that the robot can build horizontally without needing structural support the way traditional construction methods do.
Rather than trying to design the perfect structure beforehand, a 3-D-printing robot could produce a building that’s completely in tune with its environmental factors — soil moisture, temperature, wind direction and radiation levels, among others. This is how scientists think animals such as termites build their homes — by modifying the structure in response to the environment.
Since it’s solar-powered, this robot can be self-sufficient. And like living things, it could potentially create building materials out of stuff in the local ecosystem: The authors showed that the robot was able to take scoops of dirt and turn the compressed earth into building material. The researchers were even able to print with ice, which would be helpful for building on other planets.
The approach has some advantages and disadvantages, said Behrokh Khoshnevis, a USC systems engineer who works on large scale 3-D printing but was not involved in the paper. Since the foam expands as it’s applied, the robot doesn’t need to carry much material; on the other hand, this expansion may not leave as much space for the concrete filling.
“For certain limited applications it may be good,” he said. “For most applications it needs a lot of post processing.”