Army

Large format 3D printing for building construction

Mobile device utilizes local material for construction on-site

Other

U.S. Army engineers have invented a 3D concrete printer that can create buildings. The patented technologies are available via license agreements to companies that would make, use, or sell it.

A 3D printed building created by the Army Corps of Engineers, ERDC. The gantry mounted printer is seen at far right.

Current print heads struggle to flow the aggregate (pebbles) in concrete.

Common systems use a nozzle with an internal valve structure to control the flow of cement paste. This valve can clog when using material which contains aggregate.

And increasing the valve and aperture size would require a higher velocity flow and greater pumping volume. The increased volume and rate of flow make it difficult to control and precisely distribute material, increasing waste and loss of precision. It would also require increased size and weight of actuators to move the system, which in turn reduces the system’s ability to accurately position the nozzle. The higher pressures required to expel concrete, as opposed to cement paste, can also damage print heads and their connected hoses.

Army engineers developed a solution capable of printing with multiple different materials, including homogeneous materials, such as cement paste, or heterogeneous materials, such as concrete.

Functionality is accomplished by critical structures including a movable gate capable of controlling the flow of printing materials without clogging. The movable gate is rotatably connected to the printhead, allowing it to cover the discharge aperture and cut off the flow of printing material when actuated and rotated into position. A trowel on the movable gate enables manipulation of discharged printing material. A hose positioning system prevents hoses delivering printing material from disconnecting or damaging the printed structure.

The integrated, computer-controlled apparatus includes a pump assembly, noses, and printhead assembly.

Note: U.S. Patent 10,307,959 (hoses and print head) is related to U.S. Patent Applications 2018/0056544 (gantry structure) and 2018/0057405 (concrete composition).

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