Positioning

With the advent of good, inexpensive capacitive scales (yes, that $20
digital caliper is a good example), why not use cheap, rolled,
anti-backlash ball screws (not precision ones) and treat the positioning
as a servo-system? Servos are an old technology and the feedback allows
very accurate positioning and high repeatability. If you want to see how
it can be done, look at LinuxCNC (was EMC2) which has it built in.

Dave 8{)
--

"A word to the wise ain't necessary - it's the stupid ones that need the
advice."

Bill Cosby