Horizontal lines on feature/geometry/density change I've had an Ender 5 Plus for a few weeks now. It's printing great and I've got my tuning pretty good at the moment. I've noticed some horizontal inconsistencies matching feature/geometry changes. It seems to be associated with maybe layer time(?) I only have a picture from two models, but the problem will appear in other places on different models, always matching some change in the layers.
The problem is consistent all around the model and changes position with different prints, so I know it's not a mechanical problem. Say I printed a 2x2 cm tower 20 cm tall, it will not have any of these imperfections because every layer is identical.
I highly suspect the layer time/temperature change, but I don't know how to fix this, I'm a bit stumped. They both were printed at 200 °C and I'm trying a new one at 210 °C (best temperature with the spool I have) and it has the same problem. All three models are from the same spool of PLA.
Also, I use Cura with mostly default settings for the Ender 5+.
Here are the pictures :
I tried to highlight the idea, but every line matches with some change in the model

On the benchy it's harder to see, but the hull line match with the solid floor of the model, and the top ones match with the top window sill starting.
This is varying underextrusion due to loss of material to oozing in the interior of the model.
When printing the infill pattern, the nozzle doesn't follow a single continuous extrusion path, but moves from the end of one path to the beginning of the next, and under Cura defaults, does this without retracting the filament. This causes unpredictable amounts to ooze out during travel from one to the next, thereby desynchronizing the planned/intended amount of material extruded so far and the actual amount. This means, when the next outer-wall extrusion starts, there's an unpredictable deficiency between the amount of material at the nozzle to extrude, and the amount the slicer intended to extrude. The result is what you're seeing.
To fix it, you need to eliminate oozing, not just outside the model where it appears as visible stringing, but inside too. Either disable &quot;Combing&quot; entirely in Cura, or set &quot;Max Comb Distance With No Retract&quot; to something very low (0.8 mm or less). Also set &quot;Minimum Extrusion Distance Window&quot; to 0 to ensure Cura doesn't skip retractions for other reasons.
You may also want to play with extrusion length and speed. Too short or too long can be bad; 5-7 mm is the reasonable range for PLA with a bowden. Higher speed generally helps too; the printer should be able to handle 50 mm/s or faster.