Update 2/26/2015 Thanks to DesignMakeTeach for suggestions for improving this model. I've redone the model with these in mind. New file is tetrahedron_keller_2016.stl.
This model is the tetrahedron defined by equations y=−6, z=0, z=x+4, and 2x+y+z=4. The equations are printed on the model.
This model was designed and printed by my WLU summer research student Ryan McDonnell ('17). See http://mathvis.academic.wlu.edu/2015/07/14/tetrahedra/ for more information.
You may have to scale by a factor of 10 if you're using MakerWare, since it tends to import files in mm, not cm. Object is sized to be 12cm in the longest dimension, but smaller prints should work just fine.
This object was made on a MakerBot2X. We used the following settings:
0.20mm layer height
10% infill (hexagonal pattern)
We printed the object with the z=0 face as the base. Thus, we needed to add some ABS juice to the build bed to be sure the object stuck and didn't curl up at the corners.