Extrusion Problems after MMU upgrade  

Extrusion Problems after MMU upgrade

Hi everyone. I have had a Prusa i3 MK2s for about two years now and it has worked extremely well until the point that I installed the MMU (1.0) upgrade that I also purchased when the printer was originally bought, but didn't receive until later due to back-order. I knew upgrading to MMU would be tricky but I figured after two years and countless successful prints, I was ready for the challenge.

Assembly went well aside from a few minor problems. I'm having issues with my 1st layer calibration print. It loads filament fine and seems to print the front strip of material OK (although a little thin), but then it stops extruding material altogether and I end up having to cancel the print. The pulleys start slipping once it starts trying to extrude, causing the problem. I tried adjusting the tension on the pulleys both looser and tighter than the 4-5mm recommended setting with no change. At first, I thought it was having trouble with the friction of unspooling filament, so I cut off a long piece and used that with no spool resistance but no luck.

When this process happens, it will no longer let me unload the filament without the pulley skipping and chattering but not grabbing the filament. What works is if I Unload and let it fail, then Load the filament which will also fail, but will force the filament far enough forward so it shoots out a decent amount of filament from the nozzle (about 2"), but then also fails. Then when I Unload once again after doing this, it has no problem retracting the filament which is very odd because that proves the pulleys can indeed work well.

I have tried a different test object and used PrusaControl to force it to use the second filament pulley but had the exact same issues with that one as well.

Any ideas?