Branch Technology Chattanooga, Tenn.–based startup Branch Technology is using a large-scale version of this robotic arm to 3D print the core of its novel panelized wall system.

Additive manufacturing in architecture is in a race to the top—building bigger and better under tighter deadlines and with increasingly complex materials. But the technology is proving to be valuable in design and construction. Some architects are using it to push the boundaries of scale and form, while others are harnessing its precise nature to create component parts or accessories.

Chattanooga, Tenn.–based architect Platt Boyd, AIA, is working somewhere in between. He is the founder and CEO of a four-person startup, Branch Technology, that is developing a modular wall system pairing a free-form, 3D-printed open matrix core with conventional building materials. Branch Technology recently came out of stealth mode with the debut of a large-scale 3D printer that will be used to create wall modules. The printer has a 12.5-foot-long robotic arm on a 33-foot-long rail that together offer a print area of 25 feet wide by 58 feet long, allowing the team to build their modules larger and more efficiently.

Here's how the process works: The printer extrudes carbon-fiber-reinforced ABS plastic into a vertical, wall-sized grid, which is then filled in with spray-foam insulation for added rigidity. Spray-applied concrete is layered on top, followed by any kind of cladding that would normally attach to concrete, Boyd says. The plastic can be routed for plumbing and electrical, as well as to create openings for windows and doors—a challenging deviation from the free-form nature of 3D-printed construction. Fabricated off-site, the matrix cores can be trucked to the jobsite and plastic-welded there before the other materials are added.

Branch Technology A cut-out of the prototype wall shows the matrix core installed with the remaining envelope materials.
Branch Technology Branch Technology's wall system.

“We’re using that [3D printed] matrix as a formwork or scaffold for these normal construction materials,” Boyd says. “The materials really become the strength and especially once the concrete is applied, the matrix is almost irrelevant.” Structurally, that is. By combining free-form 3D printing at the industrial scale—in the same vein as the groundbreaking work of Dutch designer Joris Laarman—with the elements of a typical building envelope, Boyd’s panels release architects from the planar forms of stick-built construction, albeit at a cost. The non-load-bearing interior walls currently come in at $80 to $140 per square foot—significantly more than the cost of wood-frame or metal-stud structures.

For now, Branch Technology is making its composite wall system solely for interior, non-load-bearing applications in commercial and residential projects—in particular custom jobs “where people are looking for design freedom and flexibility," Boyd says. He anticipates the development of load-bearing and exterior walls in the next eight to 12 months. For multi-story commercial use, Boyd expects the system would be non-load-bearing and paired with a steel or concrete superstructure. Other building components rethought to incorporate the matrix technology, such as roofing systems, are in the cards though the team is still refining their process.

Branch Technology The wall system's open matrix core.

Printing the matrix—the most time-consuming piece of the system's fabrication—is one aspect they hope to improve. Boyd says they’ve printed a 7-foot-tall-by-3-foot-wide wall in 30 hours, and are currently extruding at a rate of 1.5 pounds per hour. He thinks the printer will be extruding at the goal rate of 10 to 13 pounds per hour within the year, and the team is working with Oak Ridge National Laboratory in nearby Oak Ridge, Tenn., to finesse it.

"If a building takes a year to produce, that's not feasible," he says. "The typical problem for additive manufacturing in construction has been how long it takes and how expensive the materials are to produce. On speed we're still approaching that [hurdle], but on cost we feel like it's within the realm of reason."

Branch Technology The new large-scale printer (left) with an amorphous matrix grid.