Linear Rail Eggbot Derivative

Does the world really need another eggbot? At first I didn't think so, but then I ran across Niko's eggbot design over on OpenBuilds (https://openbuilds.com/builds/niko%E2%80%99s-egg-painter-robot-openbuilds.1953/) and got super inspired. I loved the look of the extruded aluminum rails, but wanted a design that hid the ends and felt a little more balanced (where the egg motor was over the rail instead of being mounted off the side of it). This is my attempt - I hope this helps someone. Also, this is not a cheap project!

I used Niko's pen arm STLs so have not provided those here.

Instead of using a hardware store hinge for the pen arm, I cut out a piece of polypropylene and screwed it in. My goal was to eliminate the possibility of any slop in the mechanism. Polypropylene is a very resilient plastic for applications where it will be bent back and forth repeatedly. Mine came from a yogurt tub ;)

I'm sure I missed something, so leave a comment if something isn't clear ab