MMU not feeding filament  

MMU not feeding filament

Before improving my friction tool 3 liked to give me grief where it wouldn't feed filament without some help. I chalked it up to it being the center tool and some warping to prevent good pressure from the bearing. Lately, however, tool 2 has been giving me some grief that I initially decided was old/wet filament. It finally progressed to the point yesterday where I had to manually feed filament for that tool until it reached the extruder (also had to manually unload it too).

I figured that the set screws had come loose and the gears were spinning, but when I opened it up I found the gears still solid. I cleaned dust and debris out (nothing binding) and was about to button it all back up when something caught my eye. At first I thought it was just a trick of the light, but indeed the teeth of the gears were not reflecting light correctly.

I looked at it under a magnifying glass and found white dust compacted into the gears. All 5 had it, but 2 and 3 were the worst with 2 being nearly smooth because of it.

So if you are having slippage issues and the gears appear tight, look closely at the gears and see if you need to clean them. I used a metal pick I had on hand, but a toothpick should probably do just fine.