June 06, 2022

A 6,000 pound robot has the power to transform the construction industry through 3D printing.

Bovay’s civil infrastructure laboratory complex, located in the basement of Thurston Hall, has a new tenant: an industrial robot weighing approximately 6,000 pounds capable of 3D printing the type of large-scale structures that could make the construction industry more efficient and sustainable by eliminating the wasteful manufacturing of traditional materials.

The 3D printing process has already led to breakthroughs in product prototyping and biomedicine. However, when it comes to large construction projects, many questions remain about how 3D printed structures will perform in the real world.

With its ability to test and validate fabricated materials and structures of all types and sizes, the Bovay Lab is uniquely suited to implement large-scale 3D printing.

“Robot masonry (bricklaying), printing with recycled plastics and printing with large-scale metal are all exciting areas with plenty of room for growth, both in terms of science and understanding. , as well as technology and engineering,” Derek Warner, Professor of Civil and Environmental Engineering said.

“The scale of many phenomena controlling construction processes is such that they must be studied at a scale close to that in which they will be used. The same is true for some of the phenomena controlling performance. Plus, there are always unknown surprises that happen when scaling early with new technology. »

The IRB 6650S industrial robot system arrived in February, and over the past few months the lab has been practicing using the robotic system – which is essentially a long swivel arm – and running a number of test prints. medium in size, including benches and planters, even a large letter C in Cornell font.

“The robotic system is versatile and flexible,” said Sriramya Nair, assistant professor of civil and environmental engineering. “One of the ways we use it is for 3D printing concrete, but it can also be used in other ways. You can attach a welder or a laser system. You can stack bricks or attach rebar. Many tedious processes can be automated.

The robot sits on a 12-foot-long track, with a circular reach of about 12 feet, for a total coverage area of ​​up to 8 feet by 30 feet, although the lab doesn’t plan to print anything. something this big, according to James Strait, Bovay Lab’s Technical Services Manager.

System operation is a team effort. A group of people mix a pre-dosed mortar and add additives to it, such as a superplasticizer that reduces the water content of the mix and improves its flow through the pipe.

Another group uses the robot controller to regulate the amount of mix that passes through the system. When the mix reaches the robot’s extruder head and nozzle, a hardening additive is introduced so that the material thickens as it is poured.

Charissa King-O’Brien/Supplied

Getting the consistency right can be a challenge. Call it the Goldilocks dilemma.

“The lower layers must be stiff enough to hold the next layer to be printed. But they can’t be so stiff that when you print the next layer on top of it, it doesn’t stick to it,” Strait said. “You have to do the grip in there, but you can’t have it so soft that it crashes.”

The process is labor intensive, but when successful, 3D printing eliminates the need for molds and also allows for the creation of unconventional shapes – optimizations that waste less material.

“Whenever you pour poured concrete, like for a sidewalk, you have to put all the molds in place. It takes manpower, materials, everything has to be staked out. This all takes a long time,” Strait said. “Every change you make to a concrete structure, you have to change the mold or get a new mold and spend manpower to do it. It’s a lot harder than going into a computer program and to say, “Want it rounded? Click. A few hours and you’re done.”

For now, the system is 3D printing with mortar, which is technically a paste with aggregates up to 4mm in size. Anything larger than this could block and damage the pump system.

However, Nair’s team intends to build its own extruder head to print steel-fibre reinforced concrete, which uses larger aggregates capable of supporting heavier loads. This will pave the way for the lab to 3D print complete bridge components and test them.

Nair also hopes his band can create their own mix to print with, rather than relying on the manufacturer’s pre-mixed material.

“The carbon footprint of these materials is very high right now,” she said. “So that’s another goal, to reduce the carbon footprint associated with 3D printed materials.”