[CarlS] wanted to build a low cost x y table for display on teletoyland.com. He realized that to keep cost low, he could use hobby servos instead of stepper motors. Exact precision wasn’t a big issue here, so the hobby servos would be perfectly acceptable.
Though Linear hobby servos are available, he decided that the cost was prohibitive. He used normal hobby servos, but had to modify their internals to get the exact amount of travel necessary. Many people modify the hobby servos for continuous rotation, but this would cause a loss in the ability for exact positioning. Instead, he replaced the potentiometer that measures the position of the servo with a 10 turn potentiometer. This allowed him 10x the travel.
Using timing belts and drawer guides, he constructed the frame and motion assemblies. The timing belts were chosen for their cheap price and no slip construction and are pulled by custom built pulleys.
The unit is controlled via some PHP scripts, that he doesn’t expand on, via a serial connection to a SSC-32 board. The servos connect directly to the the SSC-32. Go ahead and give it a try, or watch the video to see it in action.