I am just so glad I upgraded the firmware in my MM2s -- NOT!
I bought into this helping with my MMU, even though mine had worked fine most of the time. Since I uploaded the new firmware though I have not managed to get one successful filament loading. I have even now taken apart an thoroughly cleaned the MMU2 and the extruder and just had the same problem again.
From the horrible clacking sound coming from the extruder I feel the MMU2 is not disengaging once the Extruder has the filament and then the filament bangs away as it tries to drag the filament out of the MMU2 at a faster speed than the MMU2 is supplying. Other than upgrade the firmware on both the printer and the MMU I have done nothing different to what created a lovely print just 4 days ago. Since then I've not been able to succeed in anything 🙁
When I try to load I get a whole load of horrible noises and need to turn off the printer then pull out the filament by hand as experience says it will never come out. When I get it out the filament itself is very damaged. More than just a couple of inches at the extruder end though this is fully 300mm+ that is extremely damaged and has to be cut off.
Is anyone else seeing this after doing the upgrade or is it just that my printer has caught COVID-19 or something?
That is pretty much the state I am in as well. Had a 24 hour print finish, upgraded the firmware, and I cannot load filament.
Same noises and behavior as well.
Rule 1 of upgrading: Don't do it!
Rule 2 of upgrading: Don't do it yet!
Maybe check the IR sensor in the chimney on the extruder. If the filament is pushed to the extruder by the MMU2S and then the extruder grabs it and starts feeding it, BUT doesn't register via the IR sensor that it has the filament, I could see a tug war happening because at some point I think the MMU2S would start trying to pull the filament back, but can't if the extruder has a hold of it.
I'm on the latest FW and have not experienced this issue, BUT I created the scenario when I had pulled the connector off the IR sensor before the MMU2S got the filament to the extruder (I was dealing with another issue) and then all kind of noise and nastiness started happening.
@jsw I usually don't but Covid-19 leaves us with too much time on our hands 😉 On the Prusa stream couple of nights ago they did talk about printing new stronger parts and I wonder if that is a prerequisite now, not that I have been able to find out what they meant yet.
I had a similar problem and it turned out to be an octoprint plugin problem; the filament would try to load when the hotend is cold.
i had this problem immediately after updating the firmware, although it seems the plugin had the problem before. i installed the development branch of that plugin with the fix and i haven't had a filament grind since.