H2S Filament Buffer issue - broken filament

Bambu Lab H2 Series
1

Filament was not feeding from the AMS to the toolhead, it would try and then retract and try again and eventually fail. I watched and could see that the orange piece in the filament buffer would slide to the right, but no filament would come out the other side. I manually fed filament by hand to take the AMS out of the picture and it did the same thing.

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Doing some reading, I found a few things that seemed possible - a magnet or a spring issue. I removed the filament buffer and removed the small circuit board. The spring and magnet looked fine just like the pictures on the wiki. While holding it in my hand I fed some filament through and the filament came out the other side like it should. I put the circuit board back on, reinstalled the entire assembly back onto the printer.

Now, back on the printer it has the same problem. I made it this far typing and was going to ask for help/ideas and decided to pull the filament buffer off again and give it another look before posting this message. When I disconnected the PTFE tube on the right hand side which goes to the toolhead a piece (and a very surprisingly large piece) of filament was hanging out of the filament buffer. It removed with no effort, it wasn’t stuck on anything. Put the PTFE tube back in place and everything works fine.

Here’s where I’m confused. When I removed the filament buffer the first time, this stray filament must have been in the PTFE tube between the buffer and toolhead and not fallen out? If that is the case, since it is beyond the orange piece referenced above in the path to the toolhead, how was it causing a problem at that orange piece? Wouldn’t the filament being fed in get past that orange piece and basically pushed the stray piece of filament forward and into the toolhead?

Or if the filament was not in the PTFE tube but was in fact in the filament buffer and I somehow didn’t see it, how was I able to feed filament through the buffer by hand when it was removed from the printer? If filament was there, wouldn’t it have pushed the stray piece out ?

2

It might or might not do that — it depends on several factors.
Hard to say exactly what happened, but my guess is that the broken filament was on the outside and got pushed through during your last attempt. It may also have been stuck inside the PTFE tubes and then flexed back against the buffer.