3D printing has revolutionized how we manufacture things today, from the smallest nanostructures to the tallest buildings. One institution that always seems to be right in the thick of the latest 3D printing innovations is MIT, and its materials science and design Mediated Matter group, which focuses on nature-inspired design and design-inspired nature. The research group has worked to develop a glass 3D printer and even helped outfit Icelandic singer Björk with a stunning 3D printed mask for a tour. But recently, the group took on a much larger project: creating a large, autonomous robot that constructed an igloo-like building half the diameter of the dome in the US Capitol, in less than a day.

It’s called the Digital Construction Platform (DCP), an experimental enabling technology for large-scale digital manufacturing, and is made up of a large, hydraulic arm on top of motorized treads. The team conducted a lot of research before landing on the mobile, easily customizable mechanical arm: robotic arm systems are quicker to set up, promise greater task flexibility and expandable workspaces, and can be more easily implemented with current construction methods. In order to manufacture more complex shapes, the decision was also made to have the DCP print buildings by layers.

The DCP, which also carries batteries and solar panels, has a wide reach, and also features a smaller electric arm on the end, designed for fine movements and armed with multiple positioning and stability control sensors. The smaller arm also has a suite of tools for printing, digging, and welding, which can be easily switched out when necessary, and the combined reach of both arms is over 10 meters.

Architect Matthias Kohler, who was not involved with the DCP but studies autonomous construction at ETH Zurich, said, “It’s an impressive project.”

The use of autonomous 3D printing in construction boosts efficiency and building strength, since it only puts material down where it’s needed, and it’s also safer, faster, and more precise than manual construction methods, in addition to making logistics and planning much easier. The Mediated Matter scientists who worked on the DCP published a paper about their work, titled “Toward site-specific and self-sufficient robotic fabrication on architectural scales,” in the Science Robotics journal; co-authors include MIT mechanical engineer and project lead Steven J. Keating, Mediated Matter Group’s Julian C. Leland and Levi Cai, and the group’s leader Neri Oxman, whose work we’ve long admired.

The paper’s abstract reads, “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.”

The team programmed the DCP to drive out of a warehouse, and use their new 3D printing method, called print-in-place, to construct an open-top dome structure as a test print. An electronic tip creates the structure’s outline by spraying a line of expanding foam, and the robot uses the foam to build up, layer by layer, a hollow wall used as insulation, though it can be filled later with concrete and covered in plaster. The robot also added a bench to a wall, in order to demonstrate its horizontal printing abilities. The researchers reported in their paper that the dome structure, at 13.5 hours, is the fastest building ever to be 3D printed by a mobile robot; it’s also the largest, measuring 14.6 meters across.

The team put lasers on the end of the arm that could sense the position of the electronic tip, and instead of keeping the entire arm stable, the lasers were able to counteract any unwanted movement in the rest of the arm. This has never before been used in a construction robot, and it allowed the DCP to not only have a huge range of motion and reach, but remain lightweight as well.

The DCP is able to build small structures from compressed earth, sand, metal chains, and even ice, which is first deposited as water. It can also dig, print walls with color and stiffness variation, and sense environmental cues such as radiation, making it a good possibility for repairing nuclear reactors in the future. Keating hopes that one day, the DCP can be sent up to Mars and design and build structures based on local weather and ground conditions, and collect its own materials and energy. He says that one of the great things about combining robots and 3D printing is the freedom to design nearly anything.

Keating said, “Instead of making a square building, you can make a Dr. Seuss–looking building for the same cost.”

For now, the DCP still needs a little assistance: dew settled on the dome at one point during the printing process, and caused a layer of foam to slide off before it had completely adhered to the structure; Keating was able to fix the problem by switching out the printing tip for a chainsaw and backtrack. But as the print-in-place method uses standard materials, it can be used with traditional construction techniques, which will help with eventual code certification.

What do you think of this project? Discuss in the Mediated Matter forum at 3DPB.com.

[Source: Science Magazine / Images: Mediated Matter Group]


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