As I still actively use it, I keep on improving little bits and pieces on the original design. The plotter is my learning platform - when I started, I had no idea how stepper motors work, and I didn't design electronics or programmed Arduinos for many years. Please bear that in mind while reading this page :) .
All resources (mechanical parts, electronics design, Arduino and Linux C++ code) live on GitHub - feel free to use it, reuse it and hack it. If you substantially improve on anything, or if you build something similar-ish, I'd love to hear about it!
The first working version, and a result of many iterations and failures. A presentation I made for the Arduino group can be seen here.
Improved electronics design - using substepping and current-limiting drivers significantly improved performance, accuracy, and made the plotter much much quieter.