AMS repeatedly loading and unloading

Bambu Lab P1 Series Troubleshooting
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My P1S suddenly refuses to print anything anymore. It stopped mid job last night and I haven’t been able to get it functional since. Been screwing with this for 5 hours now…

The error I woke up to was [0700-8007 151928] “Extruding filament failed, printer might be clogged”. Upon taking apart the print head I saw no blobs in the gears, and they seem to spin freely. Looking in the hotend I saw some filament, so I followed the steps here using a lighter, hex wrench, and the needle: Nozzle/Hotend Unclogging Procedure for X1/P1 | Bambu Lab Wiki

I was able to get a lot of the plastic out and the needle was able to go all the way through freely. I loaded this nozzle back in and again, I got an filament extruding error. I took the head apart and cleaned it out again. Same error. So I heated the nozzle to 220, manually loaded and unloaded the filament with the P1S screen, and I was able to get it to extrude by manually feeding a length of filament in. Starting a new print gave me the same error. I have replaced the entire hotend at this point and I still can’t get my printer to print.

This is a video (archived link) of what is happening. The AMS pushes filament into the printer head, but then for some reason, pulls it back out again. it does this on repeat. I know the print head can extrude because I was able to get it to do so manually. I have tried printing with two different PLA filaments. These filaments were working fine before this morning. I’ve turned the printer on and off again. I have no idea what is going wrong.

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I own an X1 so take this suggestion with a grain of salt… I had the same issue with my printer and it turned out to be the filament sensor. It had a sliver of filament in it that prevented it from working. After removing the sliver of filament all was well.

You can test it here to confirm if yours is working or not.

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There are a few more things you could try. Unfortunately, I could not spot how far the filament actually gets when trying to load. So I’ll make a few “blind” recommendations following the filament path:

  1. Do you have grinding marks on the filament tip? A bad clog can lead to the extruder grinding of filament, leading to a sub-spec diameter which can not be grabbed. If yes, just snip off the filament tip but also clean the extruder gears.
  2. Unlikely but possible: Is the filament round? Or below nominal diameter?
  3. PTFE path: Your set-up has a fairly long path. It may be worth checking the PTFE tubes for wear and tear. Especially the PTFE ends and the tightest corner. The Buffer PTFE ends are of particular interest.
  4. PTFE path: You can feed filament manually from the AMS to feel where there are snags. The total resistance can be just that little bit too much with even a little bit of wear. On my first X1, I tried lengthening the path 15cm. Turned out this minimal additional friction was too much.
  5. Filament sensor: Tiny wisps of filament can mess with the system. Is the path clear? Is the final PTFE end still cleanly cut at 90°?
  6. Extruder: Besides filament residue (point 1), dirt can build up over time or be pushed up from the nozzle when using the needle/“simple clog” procedure. I call the latter a travelling clog which is particularly annoying.
    Extruder clog | Bambu Lab Wiki
  7. Hope there’s nothing wrong with the extruder motor. But that should have given a different error message.
  8. Nozzle: The “simple clog” procedure never worked for me. I usually use the hex key cold pull method and repeat that a few times just to be safe.
  9. Sometimes though, a nozzle has died from curling/warping or a poop chute clog and needs to be replaced.

So I hope that there’s something at least a bit helpful in this list.

:crossed_fingers: & :four_leaf_clover:

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As an update, my printer is working again. For others who are having this same problem, what I think fixed it was in the back of the printer, there is a spring for the AMS system. I saw on a wiki somewhere that it sometimes gets stuck, and when I brushed my finger over it, the spring indeed jumped back into an extended position. However, just before this I also completely disassembled the printer head and cleaned off the gears. There was very little plastic but there were little tiny pieces here and there. After this I did some manual extruding by using the Feeding > Load option several times until I saw the plastic color change to the filament I was putting in. One of these things fixed it, so check them all I suppose and good luck.

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