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I have printed a couple weeks perfectly fine with my Ender 3. Two weeks ago I changed the firmware but the settings were all fine and resulted in good prints.

Now, suddenly during a print the extruder motor started to under-extrude.

I thought "hey, could be the file" and used a test file that printed well two weeks ago: Under-extrusion, barely a line.

I looked at the extruder, no filament grinding, no clicking from lost steps or moving against pressure. The Bowden tube is firmly seated though.

I measured what is coming out: instead of 50 mm I ordered to push into the hotend got 28.7 mm. So I went and looked at the steps/mm, which is 93, exactly what it is also on the TronXY X1, which uses pretty much the same extruder setup but for a different style, same sized gear.

I cleaned out the nozzle nevertheless, but that didn't change the results.

What might be wrong and how can I fix it?!

Edit:

  • Touching the filament while I was printing a freshly sliced test, I realized it DID lose steps, just the filament did slip back (almost) quietly. Pressing a finger on the filament made me able to feel the shiver in it.
  • Inspecting what was printed showed, that the nozzle had migrated against the print platform a little over the weeks.
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  • $\begingroup$ Can you change the stepper driver, or is this on a slotted on stepper driver print board? $\endgroup$ – 0scar Sep 2 '18 at 14:43
  • $\begingroup$ The Board can't Change them. $\endgroup$ – Trish Sep 2 '18 at 14:45
  • $\begingroup$ Sounds like missing steps, could be the stepper driver is not functioning correctly, or, the stepper is somehow missing steps. Have you tried swapping the stepper motors? $\endgroup$ – 0scar Sep 2 '18 at 21:18
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A close inspection of what happened when printing the first layer resulted in this:

  • The missing steps on the new print came from the nozzle scraping too close to the print surface, which lead to no first layer
  • Readjusting the Z-axis end stop, which had moved down, resulted in no more lost steps, but the print not sticking for the first test.
  • Releveling the bed and making sure the bar was parallel to the bed resulted in a perfect first layer.

  • Lost steps and under-extrusion could not be replicated after 48 hours of rest for the printer.

I have no idea why the print had failed due to under-extrusion during the print, but apparently, my immediate tests were flawed enough to not detect the first layer height resulting in getting almost no extrusion. This I mistook for massive under-extrusion, making me believe something else was at fault.

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Sounds similar to something I experienced with my Y-axis. The grub screw on the toothed wheel had come a little loose, and I was experiencing a reasonably consistent degree of slip.

In the extruder particularly, these locking screws might not be too obvious to check.

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  • $\begingroup$ sadly this can't be the error: after inspection, the gear is very tightly mounted to the motor and can't turn freely, the 2 grubs make it impossible for the gear to slig; one is pressing onto the flat of the motor shaft $\endgroup$ – Trish Sep 2 '18 at 10:09

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