This is a spiky ball based on the (5,2)-Goldberg polyhedron.  There are 392 spikes sticking out on all sides.  380 of them are six-sided and twelve are five-sided. 


I designed it as two identical halves to be glued together.  The solid bottom gives it good adhesion to the build platform, so it does not come loose while building.


This rendering shows that many of the spikes are cut at the equator.  When assembling it, it is something of a challenge to get the correct rotation angle for a perfect match before the glue dries.  (Hint: align the grain of the plastic filaments.)  You can build a copy for yourself with these separate stl files for black and white.  When I built it, I set the black to 1% fill density and it came out fine.

Here's a sculptural treatment of the compound of five tetrahedra.  There are five identical tetrahedra concentrically interwoven through each other.  Each is white on the outside and black on the inside.  This is an ambitious build, because the nearly horizontal bars were built without support, so it is rather hairy under the arms, so to speak. The above photo is straight from the machine, still stubbly with stray ooze.



After cleaning it up a bit by scraping it with an x-acto knife, it looks much better. To make your own copy, you can use these stl files for white and black.



Here are the two halves of a hypothetical nautilus-like shell. My goal here was to comment on the common mis-conception that the nautilus has a golden ratio spiral.  A real nautilus doesn't.  This is what a nautilus shell would look like if it were based on a golden spiral.  I built it in halves on a raft, then glued the halves together.


The inside is a bit messy at the horizontal peak, but it isn't too bad after a light sanding, especially since people mostly see the outside.  You can see I designed the inside half of the shell's thickness to be all white, so there is a continuous inner layer for strength.  The black decoration is only on the outer half.




I'm quite happy with the final result.  There's a video explaining more about it here.  If you watch carefully, you'll notice the end of the raft started separating from the platform during the build, so I taped it down with some kapton tape. The files for the whole shell are here: white, black. I cut these in half, rotated the "bottom" half to lie in the +Z halfspace, then raised the black up by the raft thickness and built them using just a white raft.  Here files for the two halves, which you can use to build it this way, but before I raised the black by my raft thickness, i.e., these are registered to be built exactly on top of each other.  Build the two "top" ones together and then the two "bottom" ones together: shell-nautilus-halves.zip




Here's a two-color mazzocchio. This is a polygonal torus which was a popular design for a hat in Northern Italy in the fifteenth century.  To make your own, here are the stl files for black and white.



Finally, I made a larger version in two colors, adding a stripe to emphasize the four triangles. You can make a copy with these stl files for white and black.  It is a nice puzzle to assemble twelve parts into the four triangles. (Hint: first make modules using a few pieces, then combine the modules.)