My CNC Etch-A-Sketch was one of my most rewarding and interesting projects, and I think that it had some of the best results. I had been wanting to design and build my own laser cutter from scratch, and was looking into the mechanics of gantry systems. I brainstormed examples with a friend, and he pointed out that an Etch-A-Sketch is just a manual plotter that uses a gantry. I then decided that, as a study for my laser cutter, I could use the Etch-A-Sketch's prebuilt gantry, and much of the same software and hardware that I intended to use for my real laser cutter to automate Etch-A-Sketch drawings.
My first rough prototype was made of cheap stepper motors, a joystick module, and a Pi Pico. By moving the X and Y axes on the joystick, I could get a motor to twist the corresponding knobs on the Etch-A-Sketch and barely make some crude lines. Armed with this proof of concept, I moved on to CAD (Computer Aided Design) and whipped up a drawing detailing the bending, drilling, and tapping of a piece of sheet metal into shape. I then added two high(er) quality stepper motors with custom-designed mounts for the knobs. With some wiring to an actual CNC control board, I had finished an important case study and an interesting novelty.