The World's Tiniest 3-D Jigsaw Puzzle

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Puzzle pieces the size of sand grains have debuted at the Karlsruhe Institute of Technology. These puzzle pieces haven’t been designed to frustrated jigsaw puzzle lovers, but to demonstrate a new process for reducing the size of injection molds. It may sound esoteric, but it’s a precise process used on making things from jet engine parts to Lego bricks.

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In ordinary injection molding, hot plastic or metal is forced into a mold by high pressure. Once the material cools, the part is taken out.

The problem is that when making lots of really small parts, it’s often necessary to have them connected by a layer of plastic or metal to make it simpler to pull them out of the molds. That adds to the cost because you have to separate them.

The engineers at Karlsruhe found a way to get around that, using metal plates to “pull” the parts out of the molds. It allows for molded objects as small as a half a millimeter in volume — the size of a grain of sand — and for making parts that are thinner and needn’t be shaped like cubes.

The molds themselves are made via X-ray lithography, a process similar to the one used to make microchips.

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Besides bragging rights for making the smallest parts, there are some very real applications. One is for watches. Right now, many watch parts have to be cut from metal or plastic and that is a less precise process than injection molding. A low-cost method of making such tiny pieces could reduce expenses. Electronics are getting smaller all the time, but it’s often hard to make the casings for such tiny devices, and now that will be easier to do.

Credit: Jochen Heneka, Karlsruhe Institute of Technology