The interior bracing structure would have been impossible to create using conventional techniques. To create the pipes, the TUM researchers used selective binding, which is a 3D printing method that involves depositing a mixture of cement and water over thin layers of sand in the pattern of the final part to be created. Once the layers have set, the excess sand can be easily removed, leaving a concrete structure behind.
The selective binding machine was built by the TUM researchers themselves, and takes up a full room in the lab at the Chair of Timber Structures and Building Construction. Sand is deposited with an automatic scattering system. A three-dimensional system of tracks makes sure the print head can be positioned at any point in the working space and that a nozzle can apply the cement/water mixture at any desired point.
Working with partners from industry, the TUM team is working on developing a 3D printer with a print head that will be equipped with several thousand nozzles. It will be able to, for the first time, manufacture objects of up to 10 cubic meters.
“That’s enough to create freely-shaped, storey-high components,” said Dr. Henke.
TUM is also working on developing extrusion-based methods of 3D printing concrete. Extrusion is the most common concrete 3D printing method, and there are many variations on the technology and materials that can be developed.
“The advantage is primarily in the high construction speed,” said Dr. Henke. “The selection of material components and formation of interior cavity structures make it possible to produce multi-functional components.”
The TUM researchers have developed a concrete with wood chips added to it. Wood chips contain a lot of air, and can provide thermal insulation and temperature regulation in both the winter and the summer. TUM has developed an extrusion system for the wood-infused concrete that puts down layers of the material as much as two centimeters thick. The system involves an extruder mounted on a computer-controlled robot arm. Using this method, TUM has already constructed prototypes 1.5 meters wide and one meter high with the lightweight wood-concrete, which is just as insulating and resilient as conventional gas-aerated concrete. It does need a bit of post-processing, though, because of its rough surface finish.
Regardless of the method, Dr. Henke is sold on 3D printing as a construction form.
“3D printing will change architecture,” he said. “The technology not only allows more versatile shaping, but also more variety, since each component can be individually designed without incurring any additional costs.”
Discuss this and other 3D printing topics at 3DPrintBoard.com or share your thoughts below.
[Images: K. Henke / TUM]