A polargraph is what I decided to call this drawing machine that I made, but it also describes the output. The machine is a simple device, that draws picture using a normal pen, some motors and some string. It is only just good enough to get the job done, and in keeping with this technical brevity, I’m going to spare you more explanations about how it works: The pictures tell the story better.

Polargraph / slow drawing show preview from Sandy Noble on Vimeo.

It’s called a polargraph because it uses a dual-polar coordinates system internally, rather than the regular cartesian system we (and computer systems) tend to use.

The mechanism is not wholly original: I have mainly taken inspiration from Hektor the spraycan robot, but in researching my machine came across prior art in the form of the AS200 drawbot and Harvey Moon’s drawing machine. And draftsmen will recognise this as a primitive, gravity assisted pen plotter. An awesome one.

Technology

The whole system is fairly technologically agnostic, but the current incarnation uses an Arduino microcontroller and an Adafruit Motorshield, along with a couple of stepper motors. The application that drives it from the computer is written in Processing. It decodes a bitmap and creates a map of the file using a polar coordinates system, recording pixel position, size and brightness. The hardware requests each pixel in turn, and renders it on the page using it’s own shading and movement algorithms.

I’m experimenting with the rigging and the gondola all the time, trying to find the best way to hold a pen stable to let me draw reasonably quickly and accurately.

I’m using bristol board and smooth cartridge paper to draw on (bristol board doesn’t come in A1 sizes), with Sharpie markers, Kuretake ZIG Writers and ZIG Millennium pens and UNIPIN fineliners for fine stuff.