Creaking + Underextrusion  

Creaking + Underextrusion

I have had my CoreOne for about a year now and it has worked flawlessly up until 3 months ago. I use this for work, and it had started to under extrude right before I took paternity leave (about two and a half months ago). Not a lot, just a few mm per layer. Enough that I could not send the product out if it was being paid for though.

Evidently the issue got significantly worse after I left. Constant under extrusion, or just pauses in filament feeding where no filament left the nozzle for 5 or more mm. When I returned the issue was still present, and the staff member who tried to 'fix' it was no longer with the company. From what I gather, he at LEAST messed with the idler tension. I found that the gears were grinding, as if spinning on the filament without pushing it. 

Where I'm at with it:
- I have relubed the planetary gears without removing them, performed a gearbox calibration, and inspected all gears to look for any damage.
- I replaced the nozzle with a brand new nozzle, same type as the previous
- I have tightened the idler screws, which increased the under extrusion and resulted in a clicking noise from the gear.
- I massively loosened the idler screws, to the point it seems wrong, like, they are barely in the latch, this helped significantly
- I've opened the idler door and inspected both the bearings and the feed gear, both appear fine. The gear is intact (no nicks) and the bearings roll freely.
- All prints are using the exact same bgcode I had used previously without issue.

After loosening the idler screws an insane amount, the problem is mostly gone. I occasionally hear a creaking from the extruder though, and I'm uncertain where it's coming from exactly. The noise was not present before the issue arose. Every 3rd layer or so, I still get a few mm of underextrusion where no filament comes out at all.

I work as a technician, and this still feels wrong. The idler screws were not this loose before, and everything on the prusa site indicates they should be flush with the holes. This feels like a fix that is compensating for another problem I'm not yet seeing. I'm out of ideas at this point and have looked at every bit of information I can find. Does anyone have any ideas what would cause underextrusion in the first place? Or what super loose idler screws might compensate for?