Some days you get into work and find out someone has made something awesome. Those are good days. When that thing is Open Source it's an even better day. This is one of those days.
Jonnanes of the Nuernberg Fablab has created the plotclock. The plot clock is built from 3mm Acrylic or can be 3D printed and consists of three 9g servos controlled by an Arduino Uno. Two servos control the arms that hold the pen and the third lifts the arms and therefor pen from the surface. The files for the machine can be found on thingiverse along with the code, the code is also in GitHub so it's double OpenSource. The Build instructions are available on the Fablab site as linked in the first sentence of this paragraph.
After some tinkering and breaking of parts we've got it together. No joy on the wiper part yet but it's a work in progress. All of the parts we broke we redesigned a little so clumsy people like our good selves don't snap them too. This was mainly increasing hole sizes slighty so self tapping can be used, which actually makes the build super easy. There's an edit to the left and right arms too, where they attach to the servo, making it easier to attach. All of the edits have been uploaded and cross referenced on Thingiverse