Layer not extruding on part of the layer only
I have this on some prints, not all, and not on all parts when I print multiple parts of the same or different things. It is really annoying because it causes the part to become weak and snap easily. Does anyone know how to fix or what is causing this? If it was at the same layer height on every print that would be one thing, but it varies on every print that has issues.
RE: Layer not extruding on part of the layer only
Most of the time when I had issues like this it was the filament. Either it wasn't feeding smoothly or it had changing diameters or melting properties. The layers look fine, so I don't think it's a mechanical issue.
Try printing at half speed and a few degrees higher temp, or use different filament to see if the problem persists.
Another thing to look at is retraction/deretraction settings (also on layer change). Too much can lead to heat creep, which would cause underextrusion, but can repair itself when it's not too bad. XL nozzles are generally more vulnerable to that so you should use as little retraction as feasible.
RE: Layer not extruding on part of the layer only
Thanks for your reply and suggestions. It does it with a number of filaments, but again not every print or every time. When printing two of the same item it might do it on one but not the other even if they aren't very large objects.
RE: Layer not extruding on part of the layer only
OK. Does it happen on every tool? Does it seem to happen everywhere on the build plate or only in certain regions? Have you checked if your build plate is really parallel to the XY gantry?
If the problem stays with the tool, you could check if the motor gear grub screw is tight and the idler moves freely, and also check for filament deposits on the main drive gear. You could also remove and inspect the nozzle, maybe it is slightly kinked (can happen in a crash or when overtightening the retaining screw). If limited to some regions it might be a kink in your PTFE tubing, or the cable moving and intermittently throttling the motor. These lingering problems are really hard to track down.
RE: Layer not extruding on part of the layer only
It does it on different tools. I can recall that it has done it on at least 3 different tools so far. I haven't verified that the build plate is really parallel other than doing auto home. I pretty much only print in the front left corner except for 2 prints so far and I don't remember where the items were located in those prints that had the failure issue. Your suggestions about the PTFE tubing or the cable moving are interesting, I'll have to pay closer attention to those things. What I don't get is why it only does it on one layer and not the whole layer, it is like it is printing the inside of the layer walls but not the outside ones.
RE: Layer not extruding on part of the layer only
It's really quite weird and I must say I haven't seen this exact problem before. In default settings, the outer perimeter is printed last. If you didn't change that, then even with no infill the nozzle pressure should be equalized before it reaches the outer wall line. But you're saying the prints delaminate, so the problem might be everywhere but is only visible in these spots.
I was asking about the build plate because it looks like there's a small angle to the layer lines and the gap. This could just be the camera though. Possible reasons would be non-parallel build plate, sagging or non-flat build plate, adhesion issues or some problem with the levelling process.
If you still have it, can you measure the height of the part in the foto on the left and right end? Is it flat on both sides when checked against a flat surface?
I also just noticed some horizontal shadows, e.g. at half height where you have the little print artifact in the bend. Again, maybe it's just the camera but they seem evenly spaced/periodic. Looks like it's the same thing but weaker, which would point to a lead screw issue (or yet again non-parallel build plate).