Bambu X1C with AMS and external spool. Has been working properly for nearly three years.
The extruder has been completely cleaned/rebuilt. The filament detector at the inlet to the extruder is functioning/green light via the touchscreen.
A new extruder and new filament detector installed with no changes.
A new nozzle installed with no changes.
The buffer was removed, cleaned (no filament was found), and re-installed. The spring goes from extended to compressed once the filament hits the extruder inlet and deadheads/compresses.
When loading the filament via the touchscreen/AMS the filament enters the inlet to the extruder. The yellow gears can be seen visually via the slot on the side of the tool head start to spin, but the filament does not go in. The gears reverse and the filament returns to the AMS spool. Rinse and repeat until the touchscreen states, “Extruding filament failed. The extruder might be clogged.” Nope, new extruder and new nozzle.
Disconnect the PTFE filament tube at the back just prior to entering the print area to allow manual feeding of the filament while the AMS tries to feed at the same time. In effect, tricking the system to allow pushing manually the filament into the extruder. Same results as using just the AMS. I don’t know if a default would occur if the buffer is not triggering.
Switch to using an external spool on the touchscreen. Hand feed the filament into the extruder per the touchscreen instructions. Once the filament hits the gears, even the very lightest touch will cause the filament to be drawn in and everything works fine.
Deduction is telling me it’s something to do with the AMS/X1C interfacing, i.e. circuit board, sensor, etc.
I would replace that PTFE run into the extruder if its been 3 years and is showing a problem, its a consumable.
After that, if the feed is still having a problem, make sure you are cutting that ptfe as squarely as possible (spare tubing usually comes with a tool to do this) and seating it all the way down in that pneumatic fitting before attempting to pull it back (to engage the teethies)
If it is still only feeding into the top but not entering, you may want to consider using a riser + unclipping the PTFE snake, or doing something else to make the final bend towards the extruder be less severe. Some people have success with a little collar that kind of stands the PTFE up more straight, but I really like risers for other reasons too.
Horrible google image search and MS paint incoming about the internals of that little fitting:
You obviously know how the system should work. I don’t know if this helps, but I would definitely replace the AMS to printer tube as suggested. I had a not dissimilar issue after used the external spool option on my P2S - It seems I forgot to unload the filament on the printer screen although I did it manually. It seemingly caused a conflict with AMS - using the printer screen interface the “unload” the already physically unloaded filament solved my problem.
The filament present sensor in the top of the extruder (Hall effect) seems to be functioning since the touchscreen shows the toolhead green light on.
The buffer is working mechanically to fully extend and compress the filament tension spring/sensor (also Hall effect). Confirmed by visual during operation and by hand test with a piece of filament.
Only the AMS is affected. The manual external spool works as intended.
From your initial post, this is real relevant alongside that picture
You’ve basically got the symptoms of the filament leading edge catching on something in the pneumatic fitting or shortly after that. Trim the last 2mm off that PTFE flush and square, really ram that home, and do a test without that printed guide installed. I dont have your specific model but that fitting might be replacable too [without replacing the whole extruder] and if so is somethign to consider.
I had a similarly puzzling failure sometime last year. Turned out the filament sensors coupler was done in.
I used the one placeholder coupler from the other side of the same PTFE ( inside of the build chamber) until the set of 3 PTFE couplers was back in stock. They contain 6 of these single side couplers.
Like many of the faults that occur on the X1, user error and confusion often are the core issue.
I believe the initial problem with the extruder being gummed up is true. Cleaning that out fixed that fault.
However, prior to extruder disassembly I tried a few other filaments that were loaded in AMS to see if they would load. The last one was HIPS, and unknowingly, the first foot or so was brittle. A small piece broke off and could be seen at the entrance to the buffer. Remove, disassemble, clean, etc. and it seems okay. But, the same fault that started with the extruder remained.
Voltage and resistance all checked out okay. But, here comes the user error parts. I mistakenly installed the buffer magnet in the wrong direction. This created the same fault appearance as the extruder, hence my confusion.
Reverse the buffer magnet and it’s printing as expected.
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