So just in time for Easter this year I put together a egg painting robot, aka “Eggbot”. The original idea comes from egg-bot.com, and was created by Bruce Shapiro in 1990.
They sell kits for about $200.
Unfortunately they are not open source. I wanted a open source version to play with, so I thought I would put together my own. (sorry I didn’t realize it was opensource, source files here). It turns out a couple of people beat me to it.
The sphere-bot is a project at Pleasant Hardware. There are designs and software posted so it is basically open source which is great.
There is a post at thingiverse for the sphere bot by Zaggo. It is a good design, it uses an Arduino (which I like) and pololu stepper drivers (which I also like). Unfortunately is made primary from MDF.
A printable version of the spherebot created by Glasswalker is on thingiverse.
This design uses 8mm (5/16″) threaded rod and bearings, 3mm and 4mm bolts. This is similar to the design fo the mendel reprap 3D printers.
There are a couple of problems I found with this design. The first problem is that the center of the latitude motor (the one that only goes back and forth) is in line with the center of the egg. That works fine for a real sphere, but causes problems for a egg.
The second problem is that there is no linkage between the servo motor and the pen mount. My sevro arm was too short to even touch the pen mount, so the servo wouldn’t disengage the pen.
I used the sketchup files provided on thingiverse to make updates to the printable design.
I added a mount for a prototyping board that I used to mount pololu drivers.
See thingiverse for more information on printed parts.