Is that done, or deemed unnecessary by most?
I understand there's a lot of variables to accuracy: I've read the ball screw primer thread, which emphasises good bearings as well as high quality lead screws and nuts/backlash setup. I've read the epoxy frame thread to death, for temperature stable rigid, vibration damped performance. High-res encoders limit feed rates for servo systems; not a concern for me (100 inches per minute would be plenty).
I want to build a large format imaging device, on the scale of 2m x 3m x 0.5m travel. I'd like to achieve 0.0003" positioning resolution in the hope that I could get 0.0006" repeatability anywhere in the x/y plane. For my application it's mostly the repeatability that I want, but accuracy would come with it. I suppose I could easily afford to lose/gain 0.0003" over 5 or 10 inches if that was useful.
I have contacts at Agilent but I know there's just about nothing they have in their catalogues that'd like the price of as a hobbyist individual :-) And nor would Optodyne, Reinshaw, etc.
How are people using interferometers in the servo feedback loop? What about the measurement delay/lag? I'm particularly interested in being able to measure squareness of gantry and tool travel.
Lasertex seem to sell a product called "LaserScaler", which would replace glass scales, it seems:
Given that this an imaging application, and I'm not actually loading up my servos with any kind of cutting etc., this makes things much easier for me - for example rigidity requirements of the design are much reduced. I think that if I also used something like the LaserScaler in my feedback loop, or as part of a start-up automatic calibration routine, I could also contemplate making my machine frame "portable" (maybe relocatable is a better word: being able to transport and then spend maybe one day to rig-up the machine would be immensely valuable).
Thoughts appreciated... especially insights into the cost :-)