Filament loading problem - seems to be particular AMS slots

Bambu Lab X Series Bambu Lab X1C
1

I’ve been running PETG-GF through my AMS and despite being abrasive (hence why I mention this) it’s been working fine until I had problems loading filament. It gets all the way to the extruder, pauses a few seconds, pulls it back and tries again a few times before declaring the nozzle must be clogged. I actually replaced the filament sensor in the extruder because what else could it be?! I’ve now found that if I load filament into slot 3 or four (where I’d not been running PETG-GF) it loads fine. The extruder filament sensor is definitely working as it does turn green on the display to show filament is present. If I stop the job while it’s got the filament loaded before it pulls it back and then push it further by hand and advance the extruder, it extrudes fine and will then print.

I’m just a bit confused as to why it would get as far as the extruder if the AMS were the fault…but can’t see how it would be anything but the AMS if it works in other slots?! Anyone got any clues here please?

2

Have you checked the PTFE tube’s to make sure there not worn? If they are it could cause friction and to much friction would make it thin the extruder is clogged. Then when you push the filament the rest of the way and the extruder pulls it , it would work.

3

if you already verified your electronics are ok,
maybe you plugged the tube badly.

I had the same issue on the 4/1 joint. It was a bad placed tube one the relative inlet. filament was hitting a millimetric step because the tube wasn’t really kissing the slot. I noticed it while pushing the filament manually. detach the ams tube and try to push the filament by hand, you’ll surely understand if there’s a blockade or (or it’s friction on the whole line)

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@silver118822 I’ve definitely changed the tube inside and outside the X1C but I think I’ve only changed one inside the AMS. It seems as well that Slot3 and 4 have stopped reliably loading too - after only a few changes. I’ll take the AMS apart and change all the tube, it just seems odd that it gets as far as tripping the extruder filament sensor but then backs out again.

@Blaster The tube where it hits the extruder? I had been having trouble with it being very difficult to remove but that way helped by replacing the filament sensor as it includes the connector. I’ve had that tube in and out a lot and I’ve trimmed the end off and even replaced the whole tube, so it would seem unlikely…but I’ll triple-check.

5

just try to feed it by hand, if you insist letting the ams do the push you will never figure why it stucks

6

I’ve just discovered that my nice Capricorn PTFE tube is known to cause problems so I’ll replace that at the same time. Again, it’s odd as there’s only one section of the stuff (between AMS and buffer) and the filament reliably gets past that section. Still, worth a try. Will try hand feeding too.

7

beware you might need a bigger size tube, check specifications…
it is not about the brand, it’s about diameter.

p.s. capricorn tube is good to be burrowed into hot ends with ptfe inliner (maybe) because its (theoretical) better high temp resistance. other than this it’s very rigid, i would not use it for a mere outer line

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Ensure that when cutting the PTFE tubing, the cut is PERPENDICULAR to the tube.

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9

Ok, parts turned up :slight_smile: New damper feet - ‘cos obviously that’s the root cause! New air filter and new standby hotends. Oh and also 4m of PTFE tube that is actually relevant :smiley: I stripped the AMS but the tubing all looked perfect so I think I must have replaced it when I was having trouble with the internal hub…that I now suspect may well have been the smaller Capricorn tubing connected to it. Had to strip some of the feeders too…because one of the desiccant pods let go its content and some of the beads ended up stuck on the grease on the cogs :man_facepalming: I also checked that the AMS internal hub extruder gear cover was perfectly fine and not chewed through.

Back together, lubed the Z squeak while doing the feet and replaced the AMS to buffer tube. So far, it’s done about 8 changes and has been good each time. So I think it’s looking like it was the tube….even though it worked fine for quite a while and even though the filament actually registered in the extruder filament sensor. Odd but seems fixed …so far!

Thanks for the pointers guys.

10

Thinking it was fixed turned out to be a little premature. I tried changing the buffer as some people had reported that was involved in the problem…and that made zero difference.

The thing that finally fixed it was about three pence worth of PETG. Holding the PTFE tube more vertical as it loads seemed to fix the problem so I stumbled across this model and installed it. So far it’s loaded first time every time since.