Fun with 3d printing

I acquired a resin (SLA) 3d printer recently, and have been working on my printing skills.  The idea is to build some helpful mathematics models, useful in geometry and topology classes.  I've always found this model useful when explaining Poincare duality.  It's the tetrahedron, together with the parts of the dual CW-complex that one can see from inside the tetrahedron.  

I created the model in openSCAD, which would perhaps best be described as an open-source CAD software package where the interface is a high-level programming language.  i.e. there is very little of the tedious drag-and-drop style interface of a traditional CAD package.  You tell the software rather explicitly, in a language akin to C, how geometric primitives are placed.   Once you are satisfied with the appearence, you export an .stl file which most 3d printers can read. 

Rough scale indicated by my 2mm Staedtler pencil. 

This is my 3rd attempt at the print.  The first one turned out well, but was a little on the thin side.  The 2nd print was almost exactly as in the picture, but while showing it off around the Math Department I twirled it in the air, and it shattered when it hit the ground.  This one has the addition of some reinforcing trusses where the dual 2-cells meet the tetrahedron edges.  Not certain if that would help much in an accidental drop, and I'm not looking forward to finding out. 

As a plastic, this type of resin prints to something of the consistency of a brittle acrylic.   I have a few other resin types and have not experimented with them all yet.  Some resins are designed more with an eye towards durability, or high-temperature applications, transparency, or burnability (wax) for casting. 

I'm hoping sometime this year my son and I will build a furnace where we can melt-down some metal and try casting metal parts.  The main advantage of these resin SLA printers over the more traditional spool-driven printers is SLA prints can be very high-resolution.  The pictured prints are at 0.05mm, i.e. the finest resolvable detail is a 0.05mm (approximate) cube.  With some resins this printer can go down to 0.025mm, although I have not tried it yet. 0.05mm is difficult to spot to the eye.  With a magnifying glass you can see the sedimentary layers.  Running your fingernail along it, you can sometimes notice the layering, as well.  But after a brief sanding the part is completely smooth.