Hey!
I noticed big prints have a somewhat imperfect look between layers, is this normal?
My printer is a Qidi Q2C that I used for about 1000 hours. No maintenance has ever been done. Should I add some grease? Retention the strings?

I am also having a similar issue with layers that have different amounts of material in them. I guess I haven't set a bias correctly.

The transition point is likely to be the bottom of the box.

Wasn't this caused by difference in layer print time, giving the lower layer more or less time to cool down causing a slightly different finish and therefore perceived colour hue? I think I read about this once.

The other two comments are partially correct, but it's not just layer time.

The plastic we print shrinks when it cools. Solid layers shrink all the way to the center, pulling in on the outer walls. Thin walls cool and shrink, but without the extra pull from plastic next to it shrinking, so it shrinks less.

Reducing layer time helps a bit, but you actually need to change your model to fix this. A chamfer or fillet on the inside lower edge will help a bit, especially if it's wider horizontally.

Even better if you can include a small section with 0% infill to decouple the internal shrinkage from the outer wall. I don't really know how to do this, myself—I think it needs to be accounted for in the model, but I suppose it might be possible with modifiers on a region of the model? (Like, maybe no infill on a cylinder that maps to the inside of the box, so only the chamfer in the bottom edge has no infill?)

huh, i think it's possible. I'll look into how to uniformize that.