Solution: Heat Creep - Beware of Red Herrings - Is it a Bad Hotend Assembly, Feeder Assembly or Extruder Motor?
I wanted to post this with hopes that it will help others if they experience what they think is heat creep.
Hello Prusa Community - After using / maintaining (4) MK3s printers successfully for about 4 years - I had an issue with under extrusion on one of my printers that had 7000 hrs on in. At first it seemed to be your typical clog (which thankfully I never had before believe it or not) but then the extrusion of filament would just stop mid-print, only to see my printer printing nothing and in the middle of the air. After troubleshooting numerous things, ultimately for me it was my extrduer stepper motor that was bad - even though it appeared to work fine during all my tests after fixing what I thought was wrong, so I completely overlooked it.
If your printer just stops extruding filament out of nowhere - BUT when you clean, check and reset things it appears to work fine again only to see the problem happens again - make sure to check the extruder stepper motor. I documented my findings in this post - I did not get any replies from the community - so continued to troubleshoot until I got it working.
During my discovery, I first followed this Prusa KB Document and then forum posts, YouTube videos and disassembled my hotend multiple times - people were mentioning cold pulls, the PTFE tube, the thermal paste on the heat-break, the thermistor not reporting the correct temp, the filament being used, gears, set screws, feeder assembly, warped parts etc. including things like filament temps and slicer settings - but I don't recall seeing anything that just blamed the extruder motor directly as the cause or how to even troubleshoot it. I also just assumed the motor was bullet proof and just didn't think about it. Now I am sure that the bad stepper motor then does cause heat creep (clogging the heatbreak etc) as the filament is no longer flowing - but the root cause was the motor.
Hope this helps.
https://www.youtube.com/shorts/qFceC0QWxzM