Innovative 3D Construction Process Could Transform Building Trades

Imagine robot sprayers guided by 3D “printing” instructions constructing the shell of a house, store, apartment building or office could in just one day without an on-site workforce. It’s already happening on an experimental basis in China, and could one day transform the U.S. market as well.

“This technique allows you to construct strong buildings more quickly at a much lower cost and with great architectural flexibility,” said Behrokh “Berok” Khoshnevis, an industrial engineering professor at the University of Southern California’s Epstein Department of Industrial & Systems Engineering in Los Angeles, “Because less labor is required, the construction is much safer for the field workforce.” To bring the 3D printing process into the private sector, Khoshnevis launched Contour Crafting, and plans to build a demonstration home in the near future using robots that spray layer after layer of concrete material in a precisely controlled pattern.

While Khoshnevis knows it will take time for this innovative process to catch on, he believes it can eventually transform the market – particularly for the affordable housing market. “Most people will continue to build with wood, steel and glass, butt there is a real need for this technology,” he said in an interview with Perspective Media. “We plan to license this technology, which can bring affordable housing to communities around the world.”

How it works

At the 2013 “Inside 3D Printing” conference in San Jose, Khoshnevis explained how Contour Crafting has addressed the challenges facing large-scale layered fabrication technology. Once the 3D design for a home or other structure has been completed, it needs to be “printed” in the real world environment.To do so, a 3D printer weighing 500 pounds could be mounted on a gantry frame and brought to a construction site. It could also be placed on rails to move back and forth on a street, constructing multiple houses in sequence. Then, one or more robotic “arms” would move around the construction site, spraying concrete or a similar material – pumped from a truck – according to the printer’s 3D instructions. The robotic machines would gradually move higher on the walls and eventually to the roof of the structure as the layers of material accumulate.

One of the biggest challenges to the process was creating a mechanism that could extrude wet cement with a special hardener so it would keep its form as each successive layer is printed. “With this process, it’s possible to construct a 2,000-square-foot house, including the floors, walls and roof, in less than 20 hours,” Khoshnevis said at the conference.

Integrating functional components

One of the big questions for the building trades is how functional components like plumbing, heating, HVAC and electrical systems can be integrated into a 3D printing system. Here are several examples of the process.

• HVAC. Basically, the robot sprayer would create a solid housing for the heating, ventilation or central air-conditioning systems, which would then be installed by contractors in those trades.
• Plumbing. Khoshnevis says the Contour Crafting process has the potential to build utility conduits within walls. “This makes plumbing automation possible,” he added.

After fabrication of a certain number of wall layers, a segment of copper (or other material) pipe may be attached onto the lower segment already installed inside the conduit. The robotics system delivers the new pipe segment and has a heater element in the form of a ring. The inside (or outside) rim of each pipe segment may be pretreated with a layer of solder. The heater ring heats the connection area, melts the solder, and once the alignment is made, bonds the two pipe segments. “PVC plumbing is also possible by using adhesives for pipe connections,” he said.

• Electrical. A modular approach similar to industrial bus-bars may be used for automating electrical and communication line wiring. The modules have conductive segments for power and communication lines, and interconnect modularly. All modules may be robotically fed and connected.

“A simple robotic gripper on manipulator attached to a Contour Crafting machine can perform the task of grabbing the component and connecting it to the component already placed within the conduit,” Khoshnevis said. “The automated construction system properly positions these modules behind the corresponding openings on the walls. The only manual part of the process is inserting fixtures into the automatically constructed network.”

• Sensors. Sensors and other devices can be implanted in certain segments of the building. “Discrete sensors may also be densely placed by a robotic arm at pre-specified locations inside any type of construction material for in-process feedback for construction process control,” he said. They also provide means for inspection and tracking variables such as temperature, humidity and vibration in completed structures.”
• Insulation.   Insulation as well as finish work, such as plastering of walls may be achieved by using a hybrid Contour Crafting nozzle that delivers multiple materials such as concrete, polyurethane, and plaster. After the walls are constructed, a conventional spray painting robotic manipulator driven by the same 3D instructions may paint each room according to desired specifications. “The painting mechanism may be a simple spray nozzle, or a large inkjet printer, making it possible to print wall paper or other desired patterns,” Khoshnevis said.
• Tiling. Tiling of floors and walls may be automated by robotically delivering and spreading grout and adhesives to the flooring. Another robotics arm would pick the tiles from a stack and accurately place them over the area treated with the adhesive material. “Often 60 percent of the time in manual tiling could be spent on alignment,” Khoshnevis said. “With an accurate robotic infrastructure in place alignment will not be an issue at all.”

Benefits of 3D printing

First developed more than 25 years ago, the 3D printing process involves creating solid objects from digital files using thin layers of plastics or other quick-drying substances like concrete. Layer after layer of material is laid down automatically, until the entire object is created.

“With this process, a single house or a neighborhood of home, each with a different design, could be automatically constructed in a single run,” Khoshnevis said. “The potential applications of this technology are include low-income and commercial housing.”

While it takes six to nine months to construct an average house in the U.S., Contour Crafting can complete custom-designed houses in a single day. “Worldwide, we will offer dignified but affordable housing constructed for low income populations,” he said. “We can also create comfortable and livable emergency shelters (not tents) for long-term usage by disaster victims.”

Khoshnevis says other benefits of the 3D printing process include a steep reduction in building wastes and harmful emissions during the construction process.

One of the advantages to Contour Construction’s approach is the ability to offer curvilinear architectural designs rather than traditional rectangular boxes, Khoshnevis added. “These new designs can give a fresh appearance to neighborhoods and cities.”

Looking to the future, Khoshnevis said 3D printers and automated robots could be used to construct livable habitats on the moon and Mars, which are targeted for human colonization before the end of the 21st century. In fact, Contour Crafting beat more than 1,000 other companies around the world to win the grand prize in NASA’s 2014 Tech Briefs “Create the Future Design.”

While 3D printing technology still needs to establish itself in the U.S. construction industry, it’s clear that this innovative technology has the potential to change other worlds, as well as the Earth.