A lot of stuff needs to be clarified. For sake of low cost, PC with parallel port will be used. I have a lot of experience with this setup controlling various devices, and old computers are practically free. Linux and GNU tools are also free. Things get a bit murkier at the end of the parallel port cable though. Options here include latches, PICs, AVRs, or Arduino like boards. I have experience with all of those, except latches - old school design. Driver part is also questionable. Prefab solutions are not free, and individual transistors are maybe too low approach (12 needed for 3 unipolar motors). Mechanical setup is even murkier, because spools, toolhead, and tool lifting are unresolved for now.