Check the extruder tension arm. If you have the plastic one it may be cracked.
It's metal, and it seems fine. I'll try adjusting it for a bit more tension and see if that works.
Edit: nevermind it is plastic. But still, seems fine.
Note that the brass toothed gear can also wear out. Maybe check it to see if there's a lot of ground-up filament in the teeth? Then check the fitting where the bowden tube goes into the extruder, make sure that isn't loose (it will be seen moving back and forth during retractions in a print). Also worth checking the bowden tube itself, make sure it's not causing a lot of drag on the filament passing through it. And for that PTFE mod in the hotend, check the friction there, it's possible to over-tighten the fitting and partially crush that tubing. You should be able to easily push filament through the hotend by hand once it is up to temp.
I assume you have something other than the stock setup for your filament roll to reduce the drag there so it's not being pulled into the extruder at a 90-degree angle? There are a number of extension arms you can print to change the angle, but the best methods are either to move the filament spool off to the side (where the filament can enter the extruder in a straight line), or print a roller that uses a bearing for changing the angle in combination with a full bearing-supported roller that the filament spool itself sits on. I still have mine in the stock position on top of the frame but with the combination of bearing objects in the last option I have practically zero friction pulling the filament into the extruder.
Finally, when was the last time you calibrated your E-steps? It's likely you actually have underextrusion on all layers, but they're getting smoothed over and are not as obvious on the alternate layers. Never hurts to check this step.
tl;dr: eliminate all friction from the spool to the hotend, calibrate E-steps.
Thank you. I recently replaced that gear as well, and the problem has gotten a bit better. I'll be sure to check everything you just mentioned.
I tightened the tension arm and now it's clicking when it reaches a piece of filament that isn't extruding fast enough. So I think that means it's an issue with the hotend not heating the filament fast enough. I'll check the friction of the mod though just to be safe, and I don't think I ever calibrated my E-steps, so I'll have to do that.
Adjusting the tension arm seems to have helped a lot, so I think you're on to something.
Yeah you don't want the arm TOO tight or you just create another friction issue. I generally find if you have a very consistent under-extrusion then it's likely the E-steps, but if the issue seems more random (some layers are great, only certain corners are bad, etc) that it comes down to friction somewhere in the line. Good luck!
You and me both, im suffering the same issue. Things to check, temperature, extruder settings, check to see if you say extrude 100mm you actually use 100mm. Tightness/cleanliness of the extruder drive, tightness of the nozzle (check this when the extruder is up to temp), and probably a ton of other things im not thinking of right now
Start with more basic troubleshooting:
Mark out 100mm length on the filament, tell the printer to extrude 100mm and see if it did. If not, remove the hotend and try again. If it did now, you have a problem with your hotend.
If it worked both times, your slicer might be setup wrong.
The OG Ender 3 has about the shittiest cheapest extruder you can design. But it sounds like you've ruled that out.
Did you ever do the hotend PTFE fix? It's prone to clogging because the Bowden tube goes all the way to the nozzle and gets pulled out during retractions.
I did, yes.
I forgot to post an update but I found the source of the issue. Turns out I'm a dumbass and I accidentally loosened my extruder's tension arm.
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