From Ken Olsen of The Maker’s Box on Tindie:

A 3D printed drawing robot you can build, program, and modify.
Robotics is the exciting intersection of a number of engineering fields including mechanical engineering, electrical engineering, and computer science. This project was designed as the basis for a two-day workshop for high school age students to introduce them to engineering principles and giving them a jumping off point for exploring their interests further. There is something for everyone here, even if it is just for the art it creates. The design goals were:
Easy to build.
Easy to program.
Did something interesting.
Low-cost so participants could take it home and continue to learn.