For a very nerdy Valentine's Day, I give you heart gears. This was inspired by Greg Frost's Broken Heart thingiverse.com/thing:4683, but it fits in the palm of your hand and can be twisted like some kind of worry ball. It makes use of the heart shape from thingiverse.com/thing:6190, the MCAD involute bevel gear script from thingiverse.com/thing:3575, and nophead's polyhole script for making properly dimensioned tap holes thingiverse.com/thing:6118.

UPDATE: If you lack a 3D printer, you can now buy these from CarryTheWhat at etsy.com/shop/CarryTheWhat.

I was daunted by the complexity of Greg's design, so this one is much simpler, having fewer gears, and a much simpler attachment design (simply thread the bolts into tight plastic holes). It also uses a smooth heart shape and is made for the hand instead of the desk.

A kinetic sculpture made using my parametric bevel gear script inspired by this: brainblog.to/item/2008/11/herz-aus-zahnraedern
I modeled the entire thing from scratch in OpenSCAD, starting with the Parametric Involute Bevel and Spur Gear script I posted some time ago. I have added an additional complexity to the movement because not only do the gears spin, but the axes of the gears rotate too.

Being a kinetic sculpture, you really need to see it in motion:
youtube.com/watch?v=Zx28cHA4_KI

Be warned that before you attempt to print this, an improved technique for attaching the gears to the central mount is really needed.

I have the openscad files for everything, although there are so many parts that it is a bit of a process generating the STLs from them.

If someone wants to collaborate on a better way to mount the gears, let me know.

This started out as an exercise in using Greg Frost's awesome involute bevel gear script thingiverse.com/thing:3575, but turned into a rather pleasing worry-ball type thing. It's also clearly influenced by Greg's broken heart thingiverse.com/thing:4683, though this has octahedral gears rather than dodecahedral, so they all mesh with each other and spin. My favorite thing about it is that you can grab two opposite gears and twist them, making the center with the other six gears spin rapidly around.

This is a sphere made of gears. The hub of the gears is off-center so that the surface breaks up when the gears turn.

This is based on emmett's cube gears ( thingiverse.com/thing:6073 ), but with a lot of improvements to the script. Rendering still takes a long time at first (as much as 10 minutes for this version), but I've added caching so that you don't have to wait that long every time. The render statements I used to do this also stop the OpenCSG renderings from looking like something homicidal impressionist clown with dyslexia painted during an earthquake. I also made the animation work, though even with the caching it won't exceed a few fps. The most important thing, though, is that I added a module to the parameters section to define the shape to cut into gears. You can now make gears out of any STL just by dropping the "import_stl" into this module.

Ok, this one is kinda meta. Continuing with the theme of making stuff into a set of gears, this is one large gear made of eight smaller ones. I used the involute gear script that was already in the scad file from the Eccentric Sphere Gears script and its predecessors, and made a gear to cut the other gears out of. I basically mashed it up with itself.

This is an extrapolation of the now infamous Penrose Triangle illusion 3D model (http://www.thingiverse.com/thing:6513). If you had trouble getting your head around that one, you're not going to find this one any easier! :)

Where the triangle used 9 cubes, this arrangement uses 31 cubes to make a larger sorta-notreally-cube.

All versions are parallax-corrected for a viewing distance of 40cm.
(the larger ones are not simply scaled up versions of the smaller ones)

BEWARE! there is a new license on my head: You, the one who prints my head, may only print my head in return for a nice photograph of the printed head. Simple no :)? Please send the photo to [hello AT unfold DOT be]. Thanks! ps, gathering a collection of photo's to put online

This is a 3d scan of my face.

Hope this counts for Bre's "Super bonus points to the first person to put a scanned medical image" :-)
brepettis.com/blog/2009/6/28/siamese-twins-and-sharing-3d-medical-files.html
True medical data from CAT scan is hard to make printable because it often is build up of voxels (3d pixels) and not a surface of triangles.

This is a 2x2x1 puzzle using just four pieces. Many designers use this puzzle as a starter project, but this one is unique in requiring only four pieces. No additional screws, pins, or other parts.

Several designers have inquired about this model since I uploaded it to Shapeways, so I'm posting the files here for the benefit of anyone who wants to learn from the source files.

If you can't build it yourself, you can buy it from Shapeways at shapeways.com/model/112492/minimis_2x2x1__hollow_.html