I met Bruce from "The Tao of motion control" he makes incredible X,Y machines "The purpose of this site is to suggest that motion control is also an emerging medium for artistic expression. Despite the universal use of motion control in industrial settings, its use by artists has been hampered by the enormous cost of commercial equipment. Because access to the tools of this medium is crucial for its exploration, one strategy open to motivated artists is building their own equipment from scrapped components flowing out of industrial sources." This one moves a metal ball over sand to make a zen garden. Link.