Looking for an economical XY (well and Z) solution that is not for the normal use

[Doddy]

Actually, thinking about it - you can design out backlash - you'll be moving from the component pick-up in one direction across both X/Y axis - so backlash doesn't really play as much a part as e.g. a router. You'll still suffer from screw accuracy, but I think you overestimate your accuracy requirement in any case. You can't eliminate backlash, but you can probably get it down to a reasonably tolerable level. You might find few people with experience in the DIY P&P domain - you might have to have a play here and come back with specific questions. Clearly you're going to be developing a lot of the system and software yourself - but I can't see anything that would particularly worry me if you're playing man-in-the-loop with the placement.

We want vids :)

[SparkyLabs]

To stop backlash can't I put a threaded item that is rotation locked to the moving body with a spring between the two to keep the table or head on the gantry always pushed one way?