The number of materials that can be produced by 3D printing has increased to include not only plastics but also glass, metal, and even food. MIT researchers are increasing that number further, with the design of a system capable of 3D printing the basic structure of a whole building.
Structures erected with this system could be formed faster and less expensively than traditional construction techniques allow, the researchers claim. A building could also be fully customized to the requirements of a specific site and the desires of its architect. Even the internal structure could be altered in new ways; a variety of materials could be added as the process moves forward, and material density could be varied to offer best combinations of insulation, strength, or other properties.
Eventually, the researchers say, this method could facilitate the design and construction of new kinds of buildings that would not be viable with traditional building techniques.
The robotic system is illustrated this week in the journal Science Robotics, in a paper by Steven Keating PhD ’16, a mechanical engineering graduate and former research affiliate in the Mediated Matter group at the MIT Media Lab; Julian Leland and Levi Cai, both research assistants in the Mediated Matter group; and Neri Oxman, group director and associate professor of media arts and sciences.
The system comprises of a tracked vehicle that has a large, industrial robotic arm, which consists of a smaller, precision-motion robotic arm at its end. This highly controllable arm can then be used to direct any conventional (or unconventional) construction nozzle, such as those used for pouring spraying or concrete insulation material, as well as extra digital fabrication end effectors, such as a milling head.
Unlike common 3D printing systems, most of which use some kind of an enclosed, fixed structure to support their nozzles and are restricted to constructing objects that can fit within their overall enclosure, this free-moving system can build an object of any size. As a proof of concept, the researchers used a prototype to construct the basic structure of the walls of a 50-foot-diameter, 12-foot-high dome — a project that was accomplished in less than 14 hours of “printing” time.
For these preliminary tests, the system fabricated the foam-insulation framework used to create a finished concrete structure. This construction technique, in which polyurethane foam molds are filled with concrete, is similar to traditional commercial insulated-concrete formwork methods. Following this methodology for their preliminary work, the MIT team demonstrated that the system can be easily adapted to existing equipment and building sites, and that it will fit current building codes without needing whole new evaluations, Keating explains.
Eventually, the system is projected to be self-sufficient. It is fitted with a scoop that could be used to both ready the building surface and obtain local materials, such as dirt for a rammed-earth building, for the construction itself. The entire system could be operated electrically, even powered by solar panels. The idea is that such systems could be installed in remote regions, for instance in the developing world, or to regions for disaster relief after a major earthquake or storm, to offer durable shelter quickly.
The definitive vision is “in the future, to have something totally autonomous, that you could send to the moon or Mars or Antarctica, and it would just go out and make these buildings for years,” says Keating, who led the development of the system as his doctoral thesis work.
But for the time being, he says, “we also wanted to show that we could build something tomorrow that could be used right away.” That is what the team did with its primary mobile platform. “With this process, we can replace one of the key parts of making a building, right now,” he says. “It could be integrated into a building site tomorrow.”
“The construction industry is still mostly doing things the way it has for hundreds of years,” says Keating. “The buildings are rectilinear, mostly built from single materials, put together with saws and nails,” and typically built from standardized plans.
But, Keating speculated, what if all buildings could be individualized and designed using on-site environmental data? In the future, the supporting pillars of such a building could be positioned in ideal locations based on ground-penetrating radar investigation of the site, and walls could have variable thickness according to their orientation. For instance, a building could have walls that taper from bottom to top as their load-bearing necessities decrease, thicker, more insulated walls on its north side in cold climates, or curves that help the structure survive winds.
The formation of this system, which the researchers refer to as a Digital Construction Platform (DCP), was motivated by the Mediated Matter group’s complete vision of designing buildings without parts. Such a vision includes, for instance, integrating “structure and skin,” and beams and windows, in one production process, and adapting a number of design and construction processes on the fly, as the structure is being constructed.
From an architectural viewpoint, Oxman says, the project “challenges traditional building typologies such as walls, floors, or windows, and proposes that a single system could be fabricated using the DCP that can vary its properties continuously to create wall-like elements that continuously fuse into windows.”
To achieve that, the nozzles of the new 3D printing system can be modified to vary the density of the material being poured, and even to blend different materials as it goes along. In the version used in the preliminary tests, the device formed an insulating foam shell that would remain in place after the concrete is poured; exterior and interior finish materials could be coated directly to that foam surface.
The system can even form intricate shapes and overhangs, which the team showed by including a wide, integral bench in their prototype dome. Any desired wiring and plumbing can be inserted into the mold prior to the concrete being poured, providing a finished wall structure instantly. It can also add data about the site gathered during the process, using incorporated sensors for light, temperature, and other parameters to make modifications to the structure as it is constructed.
Keating says the team’s analysis reveals that such construction techniques could yield a structure sooner and less expensively than present techniques can, and would also be a lot safer. (The construction sector is one of the most hazardous occupations, and this system requires limited hands-on work.) Furthermore, because thicknesses and shapes can be enhanced for what is required structurally, instead of having to match what is available in premade lumber and other materials, the total quantity of material required could be minimized.
While the platform signifies an engineering progress, Oxman notes. “Making it faster, better, and cheaper is one thing. But the ability to design and digitally fabricate multifunctional structures in a single build embodies a shift from the machine age to the biological age — from considering the building as a machine to live in, made of standardized parts, to the building as an organism, which is computationally grown, additively manufactured, and possibly biologically augmented.”
“So to me it’s not merely a printer,” she says, “but an entirely new way of thinking about making, that facilitates a paradigm shift in the area of digital fabrication, but also for architectural design. … Our system points to a future vision of digital construction that enables new possibilities on our planet and beyond.”