Much of the time I find I get prints to be within about 1% of expectations, quite often I get much better results than that. For most of my prints, I err on the printout being a tad larger than what I need, then I sand it down to expectations. Often this is 0.1mm of sanding, or less. If you’re willing to iterate the printing process several times you can of course get the tolerances very tight. It took about 4 prints, but I eventually made some LEGO pieces that were impossible to distinguish from store-bought LEGO – except the resin I printed in was far more brittle than regular LEGO.
One print that was a good “in principle demonstration” of the non-linearities was a recent tetrahedron that I printed out. Here it is.
Three of the faces came out essentially flat, but one face (the face that was facing the build platform) came out slightly spherical. It was almost flat. But it had about a 0.2mm deviation from flat. This is for a tetrahedron that is maybe 16cm in diameter.
I believe what is going on is that in the curing process there is a different shrinkage ratio in the direction transverse to the print layers, than in the other direction. I measured the local shrinkage in an old thread here.
I do not know if those estimates remain accurate as Preform and the firmware has changed many times since then. I’ll maybe run another series of experiments soon. But the general gist is that you get less shrinkage in the direction transverse to the build plane.