Persistent Filament Gear Slipping on Prusa Mini – Underextrusion and Full Stops
Hi all,
I’ve been running into persistent extrusion issues on my 5-year-old Prusa Mini and I’m hoping someone here might have additional ideas.
The problem: The filament drive gear keeps slipping and digging into the filament, which causes underextrusion and sometimes a complete stop of extrusion.
What I’ve tried so far:
- Ordered 2 new gears, but they arrived in terrible condition (burrs, damaged teeth). After some cleanup, I managed ~20 hours of good printing before the same issue reappeared.
- Replaced the Hotend PTFE tube once (a while ago).
- Mostly using the 0.4 mm nozzle, occasionally the 0.25 mm since last year.
- Tried multiple filaments (both old and new).
- Performed cold pulls about 5 times.
- Adjusted nozzle temperature up and down.
- Adjusted the tension screw (both tighter and looser).
- Cleaned the filament feed tube.
Support experience: I contacted support multiple times by email (24/7 chat seems broken). They said the gears “look fine” (though my mechanical engineering professor disagreed after inspection) and suggested fixes I had already tried. Essentially, I’m stuck without a working resolution.
My questions:
- Is there anything else I can try to troubleshoot or fix this?
- Has anyone else run into this kind of gear quality issue?
- How do I get support to recognize that the part they supplied was defective?
At this point I’m looking for any last-ditch advice before the printer becomes unusable.
Thanks in advance!
RE: Persistent Filament Gear Slipping on Prusa Mini – Underextrusion and Full Stops
I would double check the nozzle temperatures if they are in range. Recently someone had to replace the thermistor because it was reporting much higher temperatures than they actually were ( say it reported 230C while in fact it was something like 210C).
Second thing is to check that short PTFE tube if it is not melted and if it is properly compressed ao that filament does not get stuck because it is not in a melting zone.
Finally, some people switched to Bondtech https://www.bondtech.se/product/ifs-extruder-for-prusa-mini/
See my GitHub and printables.com for some 3d stuff that you may like.
RE: Persistent Filament Gear Slipping on Prusa Mini – Underextrusion and Full Stops
Thanks for the suggestions!
How would I be able to properly check if the thermistor is reporting the wrong temperature? Is there a way to measure this externally to compare it with the printer’s reading? I haven't had any previous issues with this.
As for the short PTFE tube, I can replace it, but I’ve always found it very difficult to remove without damaging it – usually I end up needing to replace it once it’s out. Do you have any tips on getting it out safely, or on how to check if it’s seated/compressed properly without fully removing it?
The Bondtech extruder does look like a solid option, but I’d prefer to save the money and get the stock extruder working reliably first if possible.