Materials that can be produced by 3D printing include not just plastics, but metal, glass, and even food. A new system called a Digital Construction Platform (DCP) was developed that can 3D-print the basic structure of an entire building. Structures built with the system could be produced faster and less expensively than traditional construction methods allow. A building could also be completely customized to the needs of a particular site and the desires of its maker. Even the internal structure could be modified in new ways; different materials could be incorporated as the process proceeds, and material density could be varied to provide optimum combinations of strength, insulation, or other properties. Ultimately, this approach could enable the design and construction of new kinds of buildings that would not be feasible with traditional building methods.

Shown from overhead, the new robotic system can 3D-print the basic structure of an entire building. The system consists of a tracked vehicle that carries a large industrial robotic arm, which has a smaller, precision-motion robotic arm at its end. (Photo: Steven Keating, Julian Leland, Levi Cai, and Neri Oxman/Mediated Matter Group)

The system consists of a tracked vehicle that carries a large, industrial robotic arm with 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 concrete or spraying insulation material, as well as additional digital fabrication end effectors such as a milling head.

Unlike typical 3D printing systems that use an enclosed, fixed structure to support the nozzles, and are limited to building objects that can fit within their overall enclosure, this free-moving system can construct an object of any size. As a proof of concept, a prototype of the system was used to build the basic structure of the walls of a 50-foot-diameter, 12-foot-high dome — a project that was completed in fewer than 14 hours of printing time.

For these initial tests, the system fabricated the foam-insulation framework used to form a finished concrete structure. This construction method, in which polyurethane foam molds are filled with concrete, is similar to traditional commercial insulated-concrete formwork techniques. Following this approach, the researchers showed that the system can be easily adapted to existing building sites and equipment, and that it will fit existing building codes without requiring entirely new evaluations.

Ultimately, the system is intended to be self-sufficient. It is equipped with a scoop that could be used to both prepare the building surface and acquire local materials — such as dirt for a rammed-earth building — for the construction itself. The whole system could be operated electrically, and even powered by solar panels. The idea is that such systems could be deployed to remote regions; for example, in the developing world or to areas for disaster relief after a major storm or earthquake to provide durable shelter rapidly.

The ultimate vision is to have something totally autonomous that could be sent to the Moon, Mars, or Antarctica to make buildings for years. In the meantime, however, the system could be used to build something that could be used right away. With this process, one of the key parts of making a building can be replaced; it can be integrated into a building site immediately.

In the future, the supporting pillars of a building could be placed in optimal locations based on ground-penetrating radar analysis of the site, and walls could have varying thickness depending on their orientation. A building could have thicker, more insulated walls on its north side in cold climates, walls that taper from bottom to top as their load-bearing requirements decrease, or curves that help the structure withstand winds. The building could, for example, combine structure and skin, and beams and windows in a single production process, and adapt multiple design and construction processes on the fly as the structure is being built.

The nozzles of the system can be adapted to vary the density of the material being poured, and even to mix different materials as it goes. The system can even create complex shapes and overhangs. Any needed wiring and plumbing can be inserted into the mold before the concrete is poured, providing a finished wall structure all at once. It can also incorporate data about the site collected during the process, using built-in sensors for temperature, light, and other parameters to make adjustments to the structure as it is built. Because shapes and thicknesses can be optimized for what is needed structurally, rather than having to match what's available in premade lumber and other materials, the total amount of material needed could be reduced.

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This article first appeared in the August, 2017 issue of Tech Briefs Magazine.

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