Robotic system can 3-D print basic structure of an entire building

The annual $8.5 trillion construction industry may in for a major redesign
May 1, 2017

Architectural-scale dome section case study for 3-D printing system (top view). For initial tests, the system fabricated the foam-insulation framework used to form a finished concrete structure. As a proof of concept, the researchers used a prototype to build the basic structure of the walls of a 50-foot-diameter, 12-foot-high dome — a project that was completed in less than 14 hours of “printing” time. (credit: Steven Keating, Julian Leland, Levi Cai, and Neri Oxman/Mediated Matter Group)

MIT researchers have designed a “Digital Construction Platform” system that can 3-D print the basic structure of an entire building. It could enable faster, cheaper, more adaptable building construction — replacing traditional fabrication technologies that are dangerous, slow, and energy-intensive in the annual $8.5 trillion construction industry.

The Digital Construction Platform system consists of a tracked vehicle that carries a large, industrial robotic arm, which has a smaller, precision-motion robotic arm (orange) at its end. This highly controllable arm can be used to direct any conventional (or unconventional) construction nozzle, such as those used for pouring concrete or spraying insulation material. The nozzles can be adapted to vary the density of the material being poured, and even to mix different materials as it goes along. The system 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, even powered by solar panels, as shown here. The system can also create complex shapes and overhangs, which the team demonstrated by including a wide, built-in bench in their prototype dome. (credit: Steven J. Keating et al./Science Robotics)

Described in an open-access paper in the journal Science Robotics, this free-moving system is intended to be self-sufficient and can construct an object of almost any size. It could enable the design and construction of new kinds of buildings that would not be feasible with traditional building methods.

A building could 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 goes along, and material density could be varied to provide optimum combinations of strength, insulation, or other properties.

Rendering showing use of the Digital Construction Platform in an urban environment, including robotic chain welding fabrication — a building as an organism, computationally grown, additively manufactured, and possibly biologically augmented. In the future, the supporting pillars of such 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. For example, a building could have thicker, more insulated walls on its north side in cold climates, or walls that taper from bottom to top as their load-bearing requirements decrease, or curves that help the structure withstand winds. (credit: Steven J. Keating et al./Science Robotics)

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 whole new evaluations. 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.

Keating says the team’s analysis shows that such construction methods could produce a structure faster and less expensively than present methods can, and would also be much safer by reducing hands-on work*. In addition, 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.

For initial tests, the system fabricated a foam-insulation framework. In this construction method, polyurethane foam molds are filled with concrete, similar to traditional commercial insulated-concrete formwork techniques. 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 even 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. (credit: Steven J. Keating et al./Science Robotics)

The ultimate 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. Meanwhile, “with this process, we can replace one of the key parts of making a building, right now,” he says.

Automated ice structure fabrication in polar environment with power sourced through rollable photovoltaic panels and materials gathered locally. (credit: Steven J. Keating et al./Science Robotics)

Fabrication with local sand to create fractal structures for future immersion in the ocean to support coral reef regrowth. Power sourced via deployable rollable photovoltaics. (credit: Steven J. Keating et al./Science Robotics)

* The International Labour Organization estimated in 2005 that more than 50,000 people die globally in the construction industry per year, accounting for 17% of workplace accident fatalities.

Abstract of Toward site-specific and self-sufficient robotic fabrication on architectural scales

Contemporary construction techniques are slow, labor-intensive, dangerous, expensive, and constrained to primarily rectilinear forms, often resulting in homogenous structures built using materials sourced from centralized factories. To begin to address these issues, we present the Digital Construction Platform (DCP), an automated construction system capable of customized on-site fabrication of architectural-scale structures using real-time environmental data for process control. The system consists of a compound arm system composed of hydraulic and electric robotic arms carried on a tracked mobile platform. An additive manufacturing technique for constructing insulated formwork with gradient properties from dynamic mixing was developed and implemented with the DCP. As a case study, a 14.6-m-diameter, 3.7-m-tall open dome formwork structure was successfully additively manufactured on site with a fabrication time under 13.5 hours. The DCP system was characterized and evaluated in comparison with traditional construction techniques and existing large-scale digital construction research projects. Benefits in safety, quality, customization, speed, cost, and functionality were identified and reported upon. Early exploratory steps toward self-sufficiency—including photovoltaic charging and the sourcing and use of local materials—are discussed along with proposed future applications for autonomous construction.