By George Hart for the Museum of Mathematics

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The rise of personal rapid prototyping machines, such as the Makerbot, RepRap, or [email protected], allows one to make a variety of geometric models. Polyhedral models, such as this 5 cm ABS dodecahedron, are fairly straightforward.

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Next is an 8cm model of a hyperboloid of one sheet, showing how it is made of straight lines. (A version made from bamboo skewers was shown in this Math Monday column a year ago.)

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And here is a tricky assembly puzzle made of twelve identical notched rods. They were dyed four different colors to help clarify the structure.

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If you have access to a 3D printer, you can build your own copies of these models from the STL files available here.

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See all of George Hart’s Math Monday columns