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Printing structures could be next step for construction

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Creating concrete buildings and structures may soon be as easy as a click of a mouse.

Creating concrete buildings and structures may soon be as easy as a click of a mouse.

Instead of pouring concrete into forms to create structural components, the next big step seems to be automating the process with massive 3D printers.

Scientists at universities worldwide are adapting 3D printing technology to drive a nozzle, pushing a concrete mix and laying a series of toothpaste-like layers, which can be hand finished to create a traditional wall or woven into custom pre-cast components.

In Shanghai, China, in April, WinSun Decoration Design Engineering used it to create 10 hut-like “homes” of 200 square metres each using a 3D rig 500 feet long, 33 feet wide by 20 feet high pumping a material made from recycled construction waste.

Electrical and plumbing utilities were installed by hand as the layers progressed.

The plan is to create 100 rigs across China, pumping out these structures, to create low cost housing.

Theoretically, at least, it’s not much of a stretch. Architects and engineers have long used CAD programs and BIM systems in their designs.

The process of what is called additive manufacturing simply plugs into those “documents” and “prints” them, though instead of a laser printer, they’re connected to a 3D printer.

Of course, the devil is in the details. 3D printing itself has been around since the 1980s, though it really only burst into the mainstream three or four years ago.

It was popular for rapid prototyping and for making models of structural designs and has been extended to almost every sector.

Extending the concept to a nozzle pouring concrete seems logical but there are many challenges said Dr. Richard Buswell, senior lecturer in building services engineering at Loughborough University in Britain who is working with architects Foster + Partners to develop 3D printing for construction.

“We are working with cement, or concrete, because it is the most common building material, but there are some challenges,” he said.

“Our mix isn’t too exotic in that we don’t put a lot of additives into it, but it has to be precise. You’re forming layers like toothpaste and so when you lay it down you want it to stay in place.

“Too stiff and you can’t push it through the nozzle and too wet and it just goes everywhere. There’s nothing really alien about our mix though it is 100 megapascals and formulated very carefully.”

In Amsterdam, Dus Architects are building a traditional style canal house in Amsterdam using a mobile 3D printer dubbed KamerMaker which means room maker.

The printer was installed this spring and can create components up to 11.5 feet high using layers of melted plastic developed by Henkel, a German-based global maker of household products and adhesive technologies.

The material is a bio-plastic made from granules and a form of Hotmelt made of 80 per cent vegetable oil which melts at 170 C.

Future iterations will look at using other recycled materials such as wood and natural stone waste.

The plan is to create components such as beams and joists, columns and other decorative features and then assemble a three-storey structure which will serve a multitude of purposes, from storage to retail to residence.

The canal house is a traditional design, which dates back 400 years.

The project is a giant laboratory with several sources of funding including an arts grant which plans to complete the structure by 2017.

Buswell said all the projects have similar goals with different paths and theirs is to create a process, which is commercially viable so they’re concentrating on double curves and other complicated shapes which aren’t easily produced via the traditional methods.

“New technology takes time to find a niche and develop a market, especially in a conservative industry,” Buswell said, noting it will be a couple of years before it’s cost effective to produce special architectural components like furniture.

Building panels could take five or 10 more years while entire skyscrapers aren’t going to be viable for a while.

Though 3D printing seems ubiquitous it’s actually been around since the 1980s, he noted, and his own research started some seven years ago.

The initial steps will likely be in a controlled environment making “precast” types of pieces.

As the pieces get larger it’s likely that the plant will be assembled on or at least adjacent to a building site.

Behrokh Khoshnevis, a University of Southern California professor, has also been working for more than 17 years on a process called “contour crafting” and he hopes to be able to create entire buildings on-site using robotics.

His plan is to assemble a rig over the footprint of the structure, once the footing and base have been dug and poured, and then use a nozzle pumping concrete with an X-Y-Z axis controlled by a computer.

In fact, the computer and program itself could be guided from almost anywhere given Internet connectivity and cameras mounted on the rig.

The value of robotic and 3D printing is multifold; it allows a combination of materials beyond cement and aggregate, there’s little waste and the material and the final product is much more controlled.

It also allows for custom pre-cast structures with a one-off configuration.

On a practical note, 3D printing can be used in hazardous environments such as other planets, in order to construct human shelter, or in radiation zones to create containment walls.

It could also be used for rapid deployment of shelters in disaster zones.

by Ian Harvey

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