Hi,
I am starting a project log to build a very low cost laser engraver out of an old HP7550A plotter and some other bits from printers and copiers. The motion of the carriage in the HP7550A pen plotter is extremely fast, and well suited for a flying optic mirror/lens system.
Here is the donor, obtained locally for $15. These plotters can be found at computer salvage stores and on ebay. The 7550A uses Pittman DC servo motors with quadrature encoders...perfect!