Oh and 2 stepper motor drivers too. Nice build for a simple drawing robot. Would be a good kid project too. Heck you could step this up a bit and have the whole interface run on the RPi
http://makezine.com/2015/07/20/build-drawbot-two-cd-drives-raspberry-pi/
detailed directions here
http://www.homofaciens.de/technics-machines-plotter-cdrom_en_navion.htm