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Large Format 3-D Printing for Building Construction

Agency: 
Dept. of Defense

The use of 3-D printing has exploded in recent years outside of the domain of one-off prototyping. One new use is the printing of large structures such as buildings. However, while print heads are very good at printing homogeneous materials, when they are tasked with printing concrete, which contains aggregate, things get hard.

Common systems use a nozzle with an internal valve structure to control the flow of cement paste. This valve can easily clog when using material which contains aggregate, such as concrete. Merely 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, thus increasing waste and loss of precision in the fabrication process. This also requires 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 have developed a 3-D printing system which is capable of printing with multiple different printing 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.

This US application number 20180086008 is related to US application numbers 20180056544 and 20180057405. The ‘544 application defines the gantry structure and printing trolley. The ‘405 application defines suitable material as a feedstock to the system.

Benefits

  • Has the potential to reduce building materials shipped by half and reduce construction manpower requirements by 62 percent when compared to expedient plywood construction
  • Rheology sensor measures the viscosity of the material
  • Elliptical hose design imparts greater flexibility and lower bend radius and prevents aggregate from clumping

Opportunity

  • Businesses can license US application numbers 20180086008; 20180056544; and 20180057405 for commercialization into new products or services

Contact

Quinton King, PhD, CLP
406-994-7795