I have a small electronics enclosure I've been trying to print for close to a week. I'm using eSun PLA+. It has text inset on the bottom, and I've played with all sorts of settings to get the text to come out nice,, but the background has defects in it. They look like under extrusion in a couple small areas near the text, but everywhere else is fine. It's not a defect in the build plate, because the defects are always in the same places on the model, independent of where the model is located on the build plate. Here's what one of the defects looks like:
If you just glance at the bottom layer Preview, it looks fine, with nothing obvious going on.
I finally sat down tonight and ran the preview line by line, and I think I figured out what is going on. Rather than doing the background in large sections, it's hopping around. The defect shown above starts with a small section of background being laid down just below the "M":
Once it's printed that small section, it pops over to the right, and starts filling in right next to where it started that area a short time before:
I think the problem is that it's printing right next to traces that haven't cooled down yet, and it's ripping them up. There are plenty of other places it could go and work on while this small section cools down, but instead, it insists on printing next to material that it put down seconds earlier. The material must be in an intermediate sticky state, because if it was cool enough, it wouldn't have an issue, and if it had just been laid down (like an adjacent pass), it isn't a problem.
I have already slowed the first layer down to 50% speed. I don't have cooling turned on to get better adhesion & avoid warping, but I may have to experiment with that. I can also try to play with Z lift & avoiding crossing the model.
I suppose it's also possible that the defects are when the small short section is initially being printed, but when I have things tuned up well, it mostly seems to affect only one or twp passes.
I certainly don't expect a quick fix for the fundamental problem, but it's something that could be improved considerably with changes to the algorithm. I haven't noticed a check box for "don't print next to stuff you put down seconds ago"
If anyone has any ideas for a work-around for now, I'd love to hear them. I'll attach a factory file in a bit. I've been printing multiple models with different processes to find a solution, and there's no need for all the near duplicates.
Thanks!