Idler Shaft Not Turning/Selecting Correct Filament
I am posting this here as a solution as it took me awhile to figure this one out. Hopefully this will help someone who stumbles upon this issue later on.
Like most folks, I ran into a multitude of issues with the MMU2S. I was able to resolve most of the issues and calibrate with a single filament. When I tried to load in multiple filaments, I noticed that the selector and LED lights were in the correct position but the idler was not. The idler shaft could turn, but didn't appear to be turning completely. I also noted that my MMU2S was not clicking on start up. The MMU2S should click on on startup as the idler motor homes the idler shaft back and forth.
The fix for this issue is briefly, but not completely, detailed here under "Idler rotating". I believe over-tightening of the idler shaft screws to be the root cause. To resolve the issue:
- Turn off and remove power to the printer.
- Loosen the M3 tension screws on the MMU2S:
- Lift and rotate the MMU2S idler body away from the puller body. Be careful not to lose the M3 tension screws and springs.
- Loosen but do not remove the idler shaft M3 screws:
- Using your thumb, rotate the idler shaft from stop to stop several times. It should provide some resistance but not be hard to move.
- Re-tighten the M3 screws on the idler shaft but only just. Do not over tighten! You can stop tightening as soon as you feel resistance.
- Test by rotating the idler shaft with your thumb from stop to stop again. It should provide some resistance but not be hard to move. It should not "catch" when it hits each stop.
- Rotate and close the idler body.
- Tighten the M3 idler tensions screws. Do not over tighten! They should be flush or just below the surface of the printed part.
- Reapply power to the printer and test by doing a first layer calibration with a different filament position.
In my situation, this has allowed the MMU2S to function between tool changes.