MMU Just Doesn't Work. Help?  

Re: MMU Just Doesn't Work. Help?

is your FINDA (?) setup correctly? I think....it uses finda for filament removal and steps for loading. I could be wrong. I don't have mine yet 8( <---sad panda

Re: MMU Just Doesn't Work. Help?

That sounds like either the idler is too tight (meaning it cant rotate the bearing to push down on the filament) or too loose and it doesn't push down enough to allow the gears to grip the filament and remove it. The idler is really a goldilocks type of thing.

Re: MMU Just Doesn't Work. Help?

I've assembled and installed the MMU and it will work fine with a single color. When I try multi-color it fails to retract the first color more than a couple of inches - leaving the filament inside the tube between the extruder and MMU. I know the MMU is capable of fully retracting the filament because sometimes it does. Sometimes it just leaves the first color fully inside the extruder... Candidly I wish I had never installed the MMU. It took a wonderful printer and turned it into basically an expensive paper weight. Help?

Next time this happens, pull the filament all the way out and look for a bite mark (a spot where the filament got chewed up by the MMU gear). It may be as much as 50cm back from the end of the filament.

If you find a bite mark, that means the filament is getting mechanically jammed somewhere. Take a photo of the end of the filament and post it here and we can offer advice about whether your ramming settings or temperature need to be adjusted. You should also check all along the filament path for any debris that might be clogging stuff.

If you don't find a bit mark, that means the MMU isn't actually pulling on the filament to try to unload it. As others have suggested, you should check the tension on the MMU idler (the two screws holding the lid down should be tightened so they're about 1mm below flush). You should also check to make sure the grub screws on the MMU gears are tight, and that the idler is tightly screwed to the stepper motor. And you should check to make sure the FINDA is properly positioned so it correctly registers when there is filament loaded in the selector.

Re: MMU Just Doesn't Work. Help?

Next time this happens, pull the filament all the way out and look for a bite mark (a spot where the filament got chewed up by the MMU gear). It may be as much as 50cm back from the end of the filament.

If you find a bite mark, that means the filament is getting mechanically jammed somewhere. Take a photo of the end of the filament and post it here and we can offer advice about whether your ramming settings or temperature need to be adjusted. You should also check all along the filament path for any debris that might be clogging stuff.

Just wanted to add onto this. If your filament is getting chewed make sure that you perform the feed length calibration. My MMU was feeding the filament halfway into the hotend which was causing the MMU to grind the filament down because it was hitting the bondtech before the bondtech was engaged to pull the filament.

Instructions on how to calibrate found here: https://manual.prusa3d.com/Guide/Service+menu+-+Individual+Filament+Calibration/842?lang=en