Filament Buffer Jammed

I had this issue a while back when using some mat filament. A build up of tiny fibers had occurred in the filament buffer causing too much friction on the filament trying to pass through. It took me a while to figure out, was very frustrating.

Actually having an issue with this myself right now.

Bambu Labs PLA-CF stuck hard and fast.

“Could you see the filament buffer spring?
Does it stuck or
Could you try to activate the slider of this filament buffer?”

I assume support means the little black thing on the left side of the spring?

There’s a “pawl” in the hub that lets the filament move in one direction while clamping down on the filament when it moves in the other direction. It rides on a spring. I think it’s that pawl that gets jammed. The spring will be compressed when it jams. That’s what they’re asking you to check. If you don’t see the spring, it’s compressed behind the jammed pawl. If you do see the spring, the hub probably isn’t where the filament is getting stuck.


Should you be able to push it back up towards the AMS reverse through the buffer ( self answer - yes or the AMS wouldn’t be able to retract and swap )

Now it’s the matter of freeing it from in there and from the tight grip of the AMS.

I took my buffer off, decided disassembly was not the right first step, reinstalled it and then just pulled hard, back towards the AMS. Didn’t move, at first. I think I might have pushed it forward and it budged, and then when I pulled back I met some initial resistance and it released. Been working fine on every print since and it’s been getting a workout with lots of filament switches. Maybe there was a burr or some plastic flashing that made it stick and I “removed” it in the process of forcing it past the obstruction while freeing it up. It happened maybe in the first 100 hours of use and I’m pushing more than 10x that now. Hasn’t reoccurred.


Woot! its clear. I took it off, uncoupled and the CF pulled right out. Now to figure out why the reloaded spools in the AMS have question marks. D: - Forgotten Spool Info more here.

Ok so awesome thing it contiunes where it left off if, but it jammed again.

Does anything from the AMS to the back of the printer through the buffer look wrong?

LOOL Ohhhh maybe a contributing factor.

Made the fix, trying again.

Nice. I think i resonded to you on another thread. Looks like you already figured it out though.

Nah its stuck again.

I find this interesting.

When it jammed yesterday, note the tip of the filament.

Where it jammed today.

Given the position is so similar its seems to be a functional / mechanical issue in the filament buffer ( I will take it apart again tomorrow to confirm )

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Took the glass lid off and its not jamming. It seems to have to with the friction of the PLA-CF and the bend radius on the hotend ptfe.

Any updates having similar issues.

I have a new machine and have the same issue, I found the easiest way was to remove the PTFE tube at the join and help it back, its not a jam just friction but obviously its a pain as you need to be about when it unloads. After reloading and loading (mistake on a print) it is not fixed but slowly getting easier to unload. As I type its starting to unload automatically again (8 x loads and unloads)

Same issue here, i did open a ticket, hopefully Bambulab is coming with a future proof fix…


I have the same problem on our 4 printer at work, this is a huge problem for us because slowling down our intensive use of the P1S printers with AMS.

The only way we found is to disconnect and reconnect the PTFE coupling at the back of the printer, just pushing a bit the filament is making the printer restart but this is a big problem. Any long term solution found ?

Have you already replaced all of the PTFE tubes? They do wear out and it sounds like you use them a lot.


thanks @JonRaymond , one of the printr has less than 2 weeks and we do have the same problem on all printers… it really looks like the buffer is blocking the filament when the ams is retracting, the two parts of the buffer making a kind of double wedge assembly blocking the wire

Some people that swapped the buffer with the hub does not have this problem anymore.

Sorry maybe a stupid question : what is the hub ?

I have had that issue since new. I have to pull on the right PFE tube on the buffer to release the filament. Then its ok for a while so I haven’t been able to figure it out. The extruder isn’t clogged and I don’t know enough about the buffer or what makes it work. Various brands and types of filament it can happen to or not.