Persistent Filament Gear Slipping on Prusa Mini – Underextrusion and Full Stops  

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/

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.

RE:

At least check its cabling first, I had some thermal runaway errors due to thermistor cables being too squeezed and reporting lower temperature in comparison to reality ( which is a bit different to your issue but cables can cause various problems especially if they are squeezed and the whole system moves causing extra cable strains and relaxations all the time).

Temperature checks could be done with something simple as food cooking thermometer, or more advanced such as multimeter with a thermocouple. But it may be just cheaper to buy a new thermistor in the first place.

I think the easiest test is with clean PETG ( or non matte), print it slow and thus the output PETG should be glossy at around 230C, if the temperature is too low or the extrusion speed is too high then it will get matte because it did not have enough time/ temperature to melt properly. You can do something like a first layer calibration with custom temperatures going down with a constant print speed.

Short PTFE tube should be possible to remove without an issue at all. If you have problems removing it with a pair of tweezers then I think that may be a sign of other issues - it may mean the assembly is incorrect or you suffer from the heat creeping from the heat block up through heatbreak and not being properly cooled by the radiator and the fan - this is a know issue with the mini and sometimes it requires proper placing of the heatbreak and reapplying the thermal paste between heatbreak and the radiator. I would also check if the three screws in the radiator are properly locking the heatbreak in its place. Some people replace the heatbreak with something better ior even replace the whole hotend to also mitigate other issues ( such as hardened nozzle in aluminium ends in damaging thread in aluminium). I switched to Slice Engineering kit for Prusa Mini and havent got any issues whatsoever.

Bondtech extruder replacement may not be enough, you may just suffer from other issues, so I believe proper melting and cooling ( hotend and a heatbreak) is more important - I would focus on that, and maybe plan extruder replacement later on.

RE: Persistent Filament Gear Slipping on Prusa Mini – Underextrusion and Full Stops

One more thing. Notice that the short PTFE tube has specific angles ar the ends (120 degrees), which helps in minimizing the gap between the tube and the heatbreak https://help.prusa3d.com/guide/how-to-trim-ptfe-tube-original-prusa-printers_22424#133076