Inconsisten first layer extrusion with large prints
I have a Prusa Mk3s+ using a smooth PEI sheet for the print bed.
When I print something large (about 1/4 of the bed SA) I get uneven extrusion in predictable spots (around the middle of the bed is low extrusion and the outer edges look good, but when I print smaller parts in the middle of bed the extrusion looks great so I am not sure what is going on), which also happens in the same exact spot when I have two parts that cover a large SA. The perimeters and brim all look good no matter what I print on every part of the bed, so it is only the solid infill. The problem fixes itself after the first layer or two and the strength/reliability of the prints don't seem to be compromised by this, so its just mildly annoying. This also started a few days ago and I haven't had issues like this before.
My two thoughts are either firmware or a warped bed, but I am a novice with 3d printing so I could be wrong. I was wondering if anyone has experienced something similar or has any ideas on what could be causing this. Thank you.
RE: Inconsisten first layer extrusion with large prints
A warped print bed can lead to inconsistent nozzle distances, affecting extrusion. Check the bed for flatness, especially around the middle. You might want to re-level the bed, ensuring that the nozzle height is consistent across the entire surface.