This knot has a special property: No matter how the knot sits on the table, it never touches the table in more than two places. This makes the knot rock back and forth easily, and roll down even very shallow inclines. It's a fun thing to have on your desk and makes a nice intro-to-3d-printing gift. Files for both thick and thin versions are included here.
For very detailed information and instructions about this object, see MakerHome, Day 110:
UPDATE: kitwallace has developed a way to use OpenSCAD to make closed parametric curves such as this one, and this OpenSCAD way fixes some meshing problems at the join point; see "Rolling Knot" at http://www.thingiverse.com/thing:230557
MORE UPDATE: kitwallace has improved even further and written a very nice post about the journey: http://kitwallace.tumblr.com/post/74713917178/openscad-revisited
Hacktastic blog: mathgrrl.com/hacktastic
Shapeways geekhaus store: shapeways.com/shops/mathgrrl
This design and all associated pictures and files are licensed under the Creative Commons Attribution Non-Commercial Share Alike license. If you want to use designs, images, or files outside of the terms of this license, please email firstname.lastname@example.org.