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I didn't have any printer-related problem for the past 6 months, but now all of a sudden my Prusa MK3S stopped extruding during printing.

This is very strange as I can easily load\unload filament and control the step motor via Settings\Move axis\Extruder. When I did so, the filament got extruded normally.

However, when I try to print something or do First Layer Calibration, nothing comes out of the nozzle. I tried changing the Live Z (maybe nozzle too low) and it didn't help. I once managed to extrude something by increasing the temperature and the flow (in the printer's menu) to a ridiculous value of 999. Obviously, this isn't the best way to solve the problem.

Is there an easy way to fix this? I only had this problem yesterday and with some midrange-priced PETG

Edit: I tried different filaments, default slicer profiles, reinstalling slicer (prusa slicer) and drivers. None of these methods really helped.

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  • $\begingroup$ If you move the extruder and hot end to where your print would start (say, 1 mm above the build surface), can you still manually extrude filament? $\endgroup$
    – Zeiss Ikon
    Commented Jun 22, 2021 at 19:06
  • $\begingroup$ @ZeissIkon I tried and had no issue. I also played around with print settings a bit and managed to get the first layer or two extruded. Still no clue as to why the rest failed $\endgroup$
    – StLuke5
    Commented Jun 22, 2021 at 21:33
  • $\begingroup$ Tried fresh or freshly dried filament? Could your filament be mislabeled nylon, and not melting at PETG temperature? $\endgroup$
    – Zeiss Ikon
    Commented Jun 22, 2021 at 23:43
  • $\begingroup$ @ZeissIkon I used branded PETG and PLA so it couldn't have been moisture and I don't have any Nylon at the moment. I think the problem occurs regardless of the filament. I will take the extruder apart and see what might be the cause. $\endgroup$
    – StLuke5
    Commented Jun 23, 2021 at 7:49
  • $\begingroup$ The brand label on the filament doesn't keep it from absorbing moisture from the air -- or did you mean "brand new"? PLA at least does absorb moisture, though not as badly as nylon; that said, however, I've got a couple spools of Amazon Basics PLA that I opened first when I got my printer (7 weeks ago now) and they still print well (kept in my air conditioned house). $\endgroup$
    – Zeiss Ikon
    Commented Jun 23, 2021 at 11:06

4 Answers 4

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  1. It doesn't seem to be heat creep. See What are ways to avoid heat creep?

  2. Have you measured the actually temperature of the heater block? You may have a failing sensor (thermistor) or sensor circuitry. Optically is the best way to measure. The least expensive way is with multimeters that come with a temperature sensor, such as a thermocouple (lowest cost about $20 U.S.).

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  • $\begingroup$ I don't think the problem is heating-related (I can load filament and extrude it manually) but it's a good idea to double check the temperature as you suggested. $\endgroup$
    – StLuke5
    Commented Jun 22, 2021 at 11:47
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I have also been experiencing this issue and found a solution. The problem started with an ABS print that somehow scarred the steel sheet, the ABS plastic was melted on so firmly it was tough to remove and left behind marks that may have ruined the coating (normally it just pops off when cold). Each print after that would leave more marks on the steel sheet, but it was still printing. Then a few prints later, the extruder would not print onto the steel sheet, it would just move around pretending to print (like this question is asking). But the extruder was not jammed, because it could unload easily, or I could force the extruder to work manually after a bad print. So the extruder was fine, but not actually printing. I tightened up the idler screw way beyond what I would normally, and then a print started extruding a little. This is when I realized that the nozzle was so close to the steel sheet that it was not able to extrude, and the nozzle was also damaging or burning into the smooth surface but not enough to really scratch it.

My solution was to run the calibration procedure again, filament immediately started printing onto the steel sheet, and then I adjusted the nozzle Z height a bit closer and now its printing fine again. Somehow the print head / nozzle got out of alignment and I've also damaged the steel sheet as well.

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As it turned out, rebuilding the extruder actually helped. I took it apart to the point where both fans were loose as well as the extruder motor and the hotend. I didn't find anything wrong after a quick look so I put it all back together.

Then i ran the first layer calibration and for some reason it worked. I know it's neither the most satisfying solution, nor the most informative one, so sorry about that. Either way, thank you for the suggestions, I still have no idea what caused the problem.

That being said, I hypothesize that something was wrong with the hotend. That is because when I had this probem, molten filament wouldn't exit the heated nozzle on its own. Now when I heat up the hotend, the filament comes out (without the motor working)

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    $\begingroup$ Sounds like a possible clogged nozzle. $\endgroup$
    – Zeiss Ikon
    Commented Jun 23, 2021 at 15:44
  • $\begingroup$ That is possible but I forgot to mention that I also took out the PTFE tube and put it back in. So that may add another factor. $\endgroup$
    – StLuke5
    Commented Jun 23, 2021 at 15:47
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I have the exact same issue. I still haven't figured out what is going on, but my next step is to work backwards.

I brought my machine in for repairs at our local shop, and the end result was "heat creep" . It worked for a few prints, then stopped. It jammed on me and in the process of removing the jam, I broke the leads to the heat block. When I decide to go back in, I will see if when I reassembled the extruder, I knocked off enough thermal paste to make a difference... :(

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  • $\begingroup$ While it is great to hear that you are working on the issue, this doesn't seem like a definitive answer, but more of a comment. Please take the tour to get a better understanding of how the Q&A mechanism of SE works - it isn't like a thread of messages that you see on other internet "forums". It might be better to either edit your answer to provide a definitive answer, if and when you can... or to (maybe) convert this answer to a comment under the question. $\endgroup$
    – Greenonline ♦
    Commented Jan 13, 2022 at 12:27

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