MIE lecturer Ali Radhi interviewed for TVO article

Ali Radhi (MIE PhD 1T9), a lecturer with U of T Engineering and an MIE alumnus recently spoke with TVO about additive manufacturing and the potential for 3D-printed homes. Radhi teaches MIE1724: Additive Manufacturing in Engineering Applications and commented on the potential benefits and challenges in using additive manufacturing to build homes.

For home construction, additive manufacturing has mainly been used to create interior and exterior walls, rather than, for example, foundations or ceilings, and the Leamington build is no exception. Unlike a wall, which can be built up layer by layer from the foundation, there’s nothing underneath a ceiling. “Building things with a horizontal shape [like a roof or a ceiling] is quite difficult, as there are no structural supports underneath when the concrete is deposited from a nozzle,” explains Radhi in a follow-up email. Given this, Comishin estimates that his technology can be used to construct about 20 per cent of a house: “That’s where we are right now.”

In best-case scenarios, 3D printing costs about half of what traditional formwork would, Radhi says, and the automated process is less labour-intensive, as fewer workers are required and machines can log longer hours. There are material savings, too. “Think about having a honeycomb inside the wall instead of having one solid wall,” he says. “So they are structurally efficient and they are lightweight, so that’s why you have a huge reduction in cost.”

Although local builders are beginning to break ground with the emerging technology, many challenges remain. Up-front costs are substantial, says Radhi, and Coughlin isn’t sure Habitat’s project would have moved forward without recent funding from the Canada Mortgage and Housing Corporation. “CMHC is a partner in this exciting project that will look to create more desperately needed housing supply by innovative means,” a spokesperson tells TVO.org in an email. “Emerging trends in 3D construction have enormous potential to help increase the supply of affordable housing.”

An entry-level machine from Twente starts at about $350,000, Comishin estimates. Radhi says that, right now, only major developers could make the numbers work, by building in high volumes over several years. (Researchers from the University of Windsor, who are acting as project managers in Leamington, are conducting a cost-benefit analysis as part of the work they plan to share.)

“Another problem with them is they have a very low what we call margin of error,” explains Radhi of cement 3D-printers. Material rapidly hardens out of the printer’s nozzle, so blunders can be costly and time-consuming. “In normal approaches of form-working, if you figure out a mistake, you can easily fix that, but concrete 3D-printing is not easy to do because it solidifies very quickly.” Anticipating some trial and error at the Habitat site, Comishin has ordered 120 tonnes of “toothpaste.”

One more hurdle, according to Radhi: “The building is limited by the size of the printer — that’s why we don’t do a lot of high-rise buildings.”

Read the full article, 3D-printed homes: Gimmick or affordable-housing solution?, on the TVO website.

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