The AxiDraw Drawing Machine (Legacy version)[This documentation is for the older-model AxiDraw, sold prior to February 2016, with white Delrin chassis. Click here for current model support.]
See it working
Here are some examples of the AxiDraw's capabilities to inspire you! (Most recent videos first.) All of the videos on this page are available in a YouTube playlist.
Playing a Xylophone on a tablet
You don't need to actually draw on something. Here I'm using a stylus to "play" a virtual Xylophone on an Android tablet. Short line segments in InkScape are used to simulate presses. The stylus is grounded to the earth pin of a mains socket so the tablet recognises it.
It's easy to make multicoloured drawings. Each colour can be split into a separate layer in Inkscape and plotted individually (using the Layers tab of the WCB extensions). You can use separate pens, as long as they're all the same diameter, but here I'm using a cheap "4-in-1" pen which makes life much easier.
The AxiDraw® is great for writing signatures. Here's a couple of examples - both were originally bitmap images and were traced over in Inkscape to form the drawing paths.
Mona Lisa with single-line TSP path
"Travelling salesman problem" (TSP) paths are an extremely neat way of drawing images to give a grayscale effect. The entire path is a single line - the pen doesn't need to be lifted at all! EvilMadScientist have a neat program called StippleGen (http://wiki.evilmadscientist.com/StippleGen) which can produce both TSP and stipple drawings from a bitmap image. I haven't tried it myself yet, but I found a ready-made SVG file of the Mona Lisa over on Thingiverse (http://www.thingiverse.com/thing:4431) and gave it a try:
Drawing on boxes
By raising the machine, it can draw on actual objects in addition to flat pieces of paper. Here's a drawing on a small plastic box using a Sharpie felt-tip marker.
A bamboo skewer is held in place of a pen and traces a design into a levelled tray of sand.
¼" veneered MDF with Sharpie marker.
Pen: 0.5mm Uni-Pin Fineliner.