Layer splitting in same place

Question

I am getting layer splits that always happen in the same place like these:

Interestingly enough, when I do multiple prints on one plate, sometimes some prints get split and others don’t. I don’t think this is a slicer settings problem or moist filament because it only ever happens at one specific place. The rest of the printed item(s) is fine.

I also don’t have warping at the edges of the upper split layer that signifies slicer setting problems. Another interesting note is that there seems to be little evenly spaced pulsating dots along each side of the split (might be hard to see in the photos).

I have checked the Z-axis for anything that has gone loose, greased the lead screws, adjusted temp, but nothing seems to help.

Edit: I recall having similar problems once with Colorfabb Economy PETG on a different printer (Artillery SWX1) but I can only recall it from memory, no physical prints to prove it so it might have been something else.

However that does lead me to think that it may in fact be something with the slicer if it happened on separate printers printing different parts, but maybe not the direct slicer settings, rather the geometry of the model causing it like r.. github said. Filament: Inkstation black PLA Printer: Creality Ender 3 with added BLTouch.

Answer 1

From your description and particularly the photos, the source of your layer splitting is an extrusion problem at the particular location, likely an indirect result of the geometry (making it mostly repeatable when the same geometry is printed again). Some possible causes for this include:

• Too much material lost to oozing in model interior just prior to this extrusion, as a result of unretracted travel (combing).
• Previous layer marred by unretracted nozzle motion over already-printed material. This tends to make the "pulsating dots" pattern you noted.
• Extrusion jam due to heat creep or trying to unretract after the retracted material had too much time to cool due to long/slow travel.
• Higher speed being achievable on these layers due to less constraint by acceleration/deceleration, reaching a speed faster than what you can actually extrude with your extruder, hotend, and temperature settings.

I would look at the slicing output in your slicer and see if you noticed anything different about the layers where it's happening.