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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
    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
    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
    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
    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
    Jun 23, 2021 at 11:06

3 Answers 3

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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
    Jun 22, 2021 at 11:47
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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
    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
    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
    Jan 13 at 12:27

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