MMU3 Doesn't accept filament
I just finished the install of the MMU3 unit on my MK4S. When trying to load the filament, the MMU3 tries to load the filament twice pulling it, and then spits it back without registering it. The end of the filament is cut sharp, I tried different filament and different ports (1 - 5), but all result in the same issue. I tested the sensor and it seems to work correctly. The light for the load just doesn't light up (as per instructions). Am I doing something wrong? What are the troubleshooting steps?
Video of loading the filament: https://storage.googleapis.com/prusa3d-content-prod-14e8-wordpress-forum-prod/2025/05/ddc680c7-loading-fail.mp4
Test of the sensor: https://storage.googleapis.com/prusa3d-content-prod-14e8-wordpress-forum-prod/2025/05/5dd93a56-sensor-test.mp4
You can see that the LED correctly sees the filament being inserted.
RE: MMU3 Doesn't accept filament
I haven't touched the buttons on the MMU3 since the upgrade,
I use the LCD Menu options load to MMU then the filament number, or 'load all'
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility.Location Halifax UK
RE: MMU3 Doesn't accept filament
The filament is probably not entering the MMU correctly aligned. The natural curve of the filament, no matter how much you try and straighten it, combined with the likely slight curve of the tube entry makes it a bit of a faff you need to get used to. Try removing the PTFE tube from the MMU, run the filament through the tube as normal but insert and load it into the MMU before reconnecting the tube. If you can feed the filament past the rollers and into the 'holding tubes' then you don't need to use the preload function as you'll have done it manually.