bonking noise when (un)loading filament
Its best shown in this video:
https://www.dropbox.com/scl/fi/ppt8x6c92vjwcbeiloe07/PXL_20250601_192728274.TS.mp4?rlkey=n6omdaqc4d4bptccj3ibo8way&st=atn3d58o&dl=1
it boils down that the entire mmu3 is shaking when (un)loading filament 1 and it clearly 'scrapes' the filament in the process.
this happens ONLY when loading or unloading filament on position 1 of the mmu3. I've also removed a piece of the filament to see whether that was the issue, it wasn't. The other filaments on 2,3,4 and 5 load normally. If I change the filament I have the same issue at 1 so it appears to be the hardware.
I have no idea whats going on, I've played around with the idler tension but to now avail.
I've also opened the thing up to see whether the pulleys are properly aligned: they are.
Any help is welcome.
RE:
That's a pretty scary noise! Have you made any more progress on the issue?
I can't tell for sure, but it looks like the idler is bouncing up and down corresponding with the rotation of the feed motor. This suggests some sort of eccentricity in the rotation for filament 1. I might suspect that the pulley for filament 1 isn't centered on the shaft in the radial direction (i.e. not the axial positioning of the pulley that is often at fault) - but I don't think the bore in the pulley is even large enough to allow for that. I'd first remove the idler and check:
- Check the idler bearing corresponding to filament 1. Make sure it's properly aligned, not tilted at all, and spins smoothly on its axis without getting hung up anywhere, and make sure the outer surface of the bearing is free from any large debris.
- Looking at the pulley for filament 1, rotate the feed motor shaft by hand. Make sure it isn't at all tilted on its axis and that its set screws are firmly tightened to the shaft, ensuring one set screw is on the shaft flat. Also check for any large debris that might be stuck in the pulley teeth.
- Make sure the motor shaft driving the pulleys isn't at all bent - that could definitely cause this kind of eccentricity. Though this requires further disassembly to check, so you might want to check it last. Remove all the pulleys from the shaft and remove the motor, then check the shaft with a straight edge (on perpendicular axes to make sure).
Next thing to check would be the filament itself. Easiest approach here is just to switch filament 1 with one of the working filaments, just to eliminate the possibility that the filament itself has significant irregularities.
It's possible that the motor is skipping steps or grinding against the filament, but this seems less likely to me since the filament itself seems to be moving relatively smoothly. In a MMU setup, this would typically be due to excessive filament path friction. You can check for this by cutting off a short length of filament and feeding it directly into the MMU without the PTFE tube from the buffer.