I think I made the disclaimer on another thread that I have zero mechanical engineering background...

I'm trying print a box on my Dreamer and want to have a pressure-style closure. I.e., the lid fits down over the box and is just enough bigger that it'll close, but will also stay on -- needs some pressure to open. I've been trying this with both round and square boxes.

Working on a round one now. The outside diameter of the bottom is 74mm. The sides of the lid are a 3mm wall, so, the inside diameter of the lid needs to be 77mm+, right? I've printed lids at 77.25mm, 77.5mm, 77.6...all the way up to 78mm, and the lid still doesn't fit over the box.

Am I missing something fundamental about the precision of the printer?

TIA