Be sure to look at my Lego page for videos, photos and to find other Lego creations.
This is the CD/DVD Plotter from http://www.sorosy.com. Building instructions are available however you must write your own programs for it. If you want to build this with one NXT set, you'll need to make-up for some parts that it uses that the set either does not have enough of or doesn't have. I've made-up for some of those on this. The plotter itself is built for plotting (writing) on optical discs. I haven't set it up to do any text, but I do have it set to draw graphics on the discs. One of the parts I used since it takes two touch sensors and I only had one available I used a HiTechnic EOPD sensor for the pen's "home position." The advantage with the EOPD is I can adjust the point at which the pen is detected for different "home positions." The light sensor detects if a CD is loaded in the plotter and the touch sensor is used for sensing when the pen is fully retracted.