Molecuar Modelling set

Inspired by http://www.thingiverse.com/thing:334917/ this goes a few steps further.

It is intended for dual extruder printers, although it can be made with a single extruder. A dual extruder will allow the labels to be in a contrasting colour. For single extruders, you can omit the label STL.

The SCAD file can generate a script (shell script, run under Unix or emulator) which when run, will call the SCAD file again and generate pairs of STLs for each atom.

I have tried to represent electronegativity by the length of a collar on each peg, although this could perhaps be improved. It would be great to be able to visually and intuitively show which bonds are higher energy!