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Khoshnevis photo by Irene Fertik
Building Custom–Designed Houses in 24 Hours USC School of Engineering researchers are at work on a fundamentally new construction technology for building houses and other structures, funded by a grant from the National Science Foundation. “The goal is to be able to completely construct a one-story, 2,000-square-foot home on site in one day, without using human hands,” says Berokh Khoshnevis, co-principal investigator on the project and a professor in the School’s Daniel J. Epstein Department of Industrial and Systems Engineering. The process, called “contour crafting,” has already won two patents, attracted the interest of an internationally known architect and won a best paper award at an important recent robotics conference. The NSF grant will support the scale-up of a system Khoshnevis has been working on for the past five years, since the idea came to him while smoothing plaster on his house. Contour crafting builds up shapes in layers by controlling the flow of liquid building materials with two movable, programmable, trowel-like tools deployed around a nozzle. Khoshnevis has developed contour crafting machines to create smaller threedimensional items in different shapes such as cubes and boxes, bowls or domes, cylinders, cones, cones coming out of boxes and rings or disks, which can be either geometrically regular or free-form. He has used materials including plaster, concrete, adobe, plastic and a paste of wood particles mixed with epoxy. Guided by computer programming based on CAD-CAM representations, the contour crafting nozzleand-trowel system molds these materials into shape while they are still semi-liquid. In order to perfect contour crafting
programming and controls, Khoshnevis recently began working on the project at the School’s Information Sciences Institute (ISI), a nationally recognized facility specializing in computer research. Contour crafting is derived from an established technology called rapid prototyping. Rapid prototyping systems have similar computer-controlled head mechanisms that build up successive thin layers, usually of specialized or exotic materials, to create 3-D models, or prototypes. The prototypes then are used to make molds for casting or die-casting metal or plastic manufactured products.
Contour crafting builds up shapes in layers by controlling the flow of liquid building materials with two movable, programmable, trowel-like tools deployed around a nozzle. The goal of contour crafting, by contrast, is not to make a prototype, but to create a finished product. The unique double trowels precisely control a flow of material from the nozzle and allow much cheaper and more durable materials to be applied in thicker layers. Khoshnevis’ contour crafting system has already made larger objects than other rapid prototyping systems. By making the nozzle still bigger and mounting it on a overhead gantry system, a six-cable “Robocrane” system or even
Professor Berokh Khoshnevis on freestanding, wheeled robotic units, Khoshnevis believes contour crafting can erect building-sized structures, layer by layer. The NSF grant will give him the resources needed to test this theory. In the first construction design he plans, the nozzle begins by creating a hollow wall outline about a foot wide, with each layer perhaps 6 inches high, through the entire footprint of the building, including external and internal walls. On the next pass, the machine raises the hollow outline by another layer—while filling the hollow left after the first pass with more material. Repetition of the process creates a solid cement wall. The gantry system—an overhead beam mounted on two uprights, running on parallel rails—could create a succession of houses in a row, each programmed to have its own design. Speed is limited mainly by how fast each layer dries sufficiently to allow another to be put on top. The system is flexible enough to handle additions to the basic scheme. For example, a robot arm can continually insert coils of steel rebar to make the wall stronger. Inserting hollow conduits, either vertical or horizontal, for wiring and plumbing will be easy, Khoshnevis claims. Khoshnevis says the Pasadena-based California Institute of Earth Art and Architecture has offered a building site for a contour crafted adobe structure. He acknowledges the scale-up of his continued on page 30
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