Jon Wise demonstrates his Raspberry Pi 3D Printer, he is using a pen in the demo but it can use an extrude to print items. The mechanical movements leek very complex when compared to a standard XY table that is controlled using 2 stepper motors. The Pi has enough number crunching ability to get the job done though. I can’t wait to see this printing a complex shape, the movements are interesting to watch, it reminds me of the robot hands that use angular joints to move around.