Makelangelo is a polar-graph based drawing device that use flat CNC-cut construction techniques to pull a gondola-like pen holder around a surface to draw pictures. Designing my own version was a fun project to use with my 3d printer. The firmware is stock Makelangelo running on an Adafruit Feather. The drawing software and remote instruction sending server are custom, Node JS based application running on a Raspberry Pi Zero.
The design project broke down into six discrete pieces. Back-side holders attach to a standard size aluminum bar and contained a notch that hold a large suction cup. The other side included a mounting bracket for NEMA 17 Stepper motor. The bobbin is a cylinder that attaches to the stepper motor shafts via friction and has a mechanism to hold and wrap string around the diameter of the cylinder. The gondola needed a mechanism to hold a pen, arms that would hold the end of string, and a mounting device for a micro servo. The needle is a small flat piece that attaches to a servo arm and allows the gondola to come closer or further away from the window.