I had some stepper motors laying around and thought it would be fun to make an egg plotter. Although it's been done before, I decided to design my plotter from scratch. My goal was to minimize the use of non-3D printed components, and keep the 3D printed parts easy to print and modest in terms of filament use.
My design uses a four-bar linkage for the pen arm in order to minimize distortion due to the egg's curvature. It holds extra-fine sharpie markers. The design allows for a +/-60 degree range in the Y axis, but the arm will interfere with the chucks past 54 degrees unless an egg is mounted, so be mindful of that when doing dry runs.
Rather than use eggbot's software stack, I opted to use Marlin firmware and Inkscape's gcodetools extension.
Check out the README.txt for the hardware list and more details.
Special thanks to jarac for the NEMA 17 motor STL
And to StartRobot for the micro servo STL
Mad Maker PLA
The only part that needs a bit of support is the bearing block.