Design and redesign

I keep working on my slide scanner. I've itterated on the mechansim that hold the slide for photography at least half-a-dozen times, each time getting closer to something I can make with my 3D printer.This actually gets to one on my pet peeves about additive 3D manufacturing: tolerances. The tolerances for this is measured it hundredths of inches, the precision I need for many of my designs is measures in thousandths of inches.This is annoying, but nor really a problem. This just gives me the opportunity to make the designs better.Almost every design I can make with my 3D printer I could make with a classic CNC mill (or a regular mill, of course)... but I don't have the luxery of having that... so I have to come up with new ideas on how to solve the problems given the tools I have on hand.