Prusa Mini under-extruding in patches - Cannot figure out why
 
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Prusa Mini under-extruding in patches - Cannot figure out why  

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UjinDesign
(@ujindesign)
Estimable Member
Prusa Mini under-extruding in patches - Cannot figure out why

Hi Prusa forum.

I bought a second hand Prusa Mini and I've got some extrusion-problems I don't know how to solve. When printing a simple 100x100x1 sheet, the print starts off with a beautiful and essentially perfect first layer. However, after a few layers the printer starts to seriously under-extrude, looking almost as if the printer fails to extrude properly for a short while and then continueing again. See attached image.

Does anybody know what might be the problem? I have:

  • Changed the hotend PTFE tube, double-checking that there is no filament residue before inserting the new one.
  • Replaced the nozzle with a completely new one.
  • Loosened the idler lever screw on the filament sensor.
  • I think I have a sensible tension on the extruder idler lever screw. I tried tightening it 1 turn and printing the plate again but same issue occured. -
  • Have achieved essentially perfect z-offset (printing on the satin sheet).

Thanks in advance! 

Posted : 11/07/2025 9:56 pm
_KaszpiR_
(@_kaszpir_)
Noble Member
RE: Prusa Mini under-extruding in patches - Cannot figure out why

Check the wear out of the bowden tube between the extruder and the heatbreak 

See https://forum.prusa3d.com/forum/hardware-firmware-and-software-help/how-often-to-replace-various-parts-on-the-mini-a-proposed-regular-part-replacement-schedule/

See my GitHub and printables.com for some 3d stuff that you may like.

Posted : 12/07/2025 7:30 am
1 people liked
UjinDesign
(@ujindesign)
Estimable Member
Topic starter answered:
RE:

Thanks for linking this amazing resource. It turns out this probably was just a simple under-tensioned extruder idler lever screw, but what you linked is very good to know in the future. 

Posted : 12/07/2025 4:20 pm
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