MMU2s keeps stripping the filament in use at the end of a print when unloading
More often then not my MMU2s will carve out a groove in the filament about 80% of the time when a print finishes and its trying to unload the filament. I feel it may be because the heat on the hotend is being turned off at the end of the print and by the time the process to unload the filament starts the filament has hardened enough in the nozzle that it can't be pulled out. I've tried on both normal and stealth modes (always the same on both units). I have a silicone sock on my hot end so the fan doesn't cool it too fast or affect in print fluctuations. So then I have to open the MMU up, cut off the bad part and throw away 2 feet of filament. It happens on all 5 channels too. I've tried tight tension and loose tension to barely any tension on the bolts that hold the bearings in place. Its happened on brand new prusament filament, brand new hatchbox filament, and stuff up to 6 months old. I'm just wondering if this is happening to anyone else?
RE: MMU2s keeps stripping the filament in use at the end of a print when unloading
Check the retraction tightness. With the machine turned off, see if you can manually pull the filament out (after it is pulled up from the hot end some, so it does not stick when it is cooled down, of course). I found my retraction wallet was causing the filament to not retract...I could not pull it backwards by hand. Once I removed the wallet, everything moved easily and properly.
I am now trying my third different retraction method to see what works best. My big requirement is to not be exposed to air (defeats the purpose of a drybox if a few feet of filament is always exposed to air), which makes it harder.