Filament: Bambu Lab Basic Black PLA, Bambu pla mate and now recently 3rd party pla
The Problem:
At first this was happening: Every 3 to 5 prints, the printer throws an “unable to feed filament into extruder” error during the loading phase. When I check the AMS, the filament is physically damaged at the feeder gears—the 1.7mm filament is ground down to a 1.2mm trench. This happens across at least two different AMS ports. Cutting out the damaged filament temporarily resolves the issue for the next few prints.
Today it’s not feeding anymore. From any ams 2 pro port. Ams ht sometimes have lucky case and feeds in like 3rd atempt
Troubleshooting Steps Taken:
AMS Hub Cleaning: Disassembled the AMS Pro 2 internal hub per Bambu support instructions and blew it out with compressed air. Found zero debris or residue. The issue happened again on the very first print after reassembly.
Cutter Replacement: Replaced the toolhead filament cutter blade with a brand new one to rule out blunt/mashed filament tips causing snags.
PTFE Tube Replacement: Completely replaced the internal PTFE tube leading from the back of the printer to the toolhead.
Manual Push Test (Full Path): Manually pushed filament from an external spool through the system. It passes the rear buffer with some resistance, but hits a massive wall of resistance at last bend before tool head (inside the drag chain area). I cannot just push by force; I have to violently wiggle/jerk the filament in short bursts to force it past this point.
Buffer Bypass Test: To isolate the buffer, I disconnected the tube after the buffer and fed the filament directly into the printer’s internal routing. Result: The resistance at that 5-7 cm mark was still there, but roughly 3 times less severe. I was able to load the filament without jerking it. The buffer slider springs feel perfectly smooth and bouncy, but the buffer seems to be severely amplifying the downstream friction.
Visual Inspection of the Tube: I took a photo of the toolhead when it is parked at its starting point. The newly replaced internal PTFE tube forms a very aggressive, tight bend/kink right where it exits the cable chain and enters the toolhead.
Printing with auxiliary right nozle:
Printing with auxiliary right nozle path seems fine
My Current Theories:
It seems like the tight bend in the PTFE tube at the drag chain (5-7 cm before the toolhead) is creating a natural bottleneck. When the filament hits that tight corner, the backpressure causes it to bind up inside the rear buffer, multiplying the friction until it exceeds the AMS motor’s torque, resulting in the gears grinding the filament at the spool.
Or it could be a buffer issue. How to really confirm that?
Questions for the community:
Does anyone have reference photos of the correct factory PTFE tube routing/length for the X2D left hotend when parked at the scrubber? I suspect my replacement tube is the wrong length and creating too sharp of a bend.
Is it normal for a healthy rear buffer to triple the friction when pushing filament by hand?
Your PTFE tubes look to be too long. Try cutting 10cm off and test. Cut again if needed, just don’t go too short or you’ll need to replace them. My X1C was the same way, I ended up cutting off about 20cm if I recall and it really improved or reduced the friction…
Never thought of this. Will definitely worth trying as I have some spare PTFE tube ordered from Bambu. Its in different color, but hopefully it does not matter.
Haven’t yet made a single cut. Is using scissors good or beter that scratch tool from Bambu or else?
At the time I didn’t check for the required lengths. I just used some common sense, your pic shows a really tight bend just before the extruder, it needs to be more gentle. I did make sure the tube was in the clips and or chain properly but in the end cutting mine just a little bit made all the difference for me.
Another thing to consider would be a riser for your top, that can make a big difference as well, keep in mind I’m suggesting this based on my X1C, I’m sure the P2S suffers the same problem, there really isn’t enough height for the tube(s).
Also for past few days I ran out of bambu filament and ordered from local manufacturer. So that might also be related
Issue is rarer, but still there
Manual load from external spool are way way easier
AMS feed now does not fail every time, but still fail quite often.
Longer prints fail to pull after a print. For example During a night print finished and got an error during pull. So in morning decided to do a clean main extruder following this: X2D Extruder Clog Cleaning Guide | Bambu Lab Wiki but when disconnected PTFE tube found that there is no filament in the head, it’s ended a few cm before head. Removed hotend and tried pushing filament through extruder and could do that with a extruder resistance.
Hard part was manually puling fillament back to ams. Felt quite big initial resistance even with ams filament hub button depressed
So instead of extruder cleaning did a buffer disassembly for possible cleaning following this Replace Buffer PTFE Tube Connector for X2D | Bambu Lab Wiki but it was all clear inside, no hunk, no stuck filaments parts, all was quite tidy.
As of now it works for ~30-40 min prints, loading still experience repeats of fillament rolling out fully and not reaching head, or sometime reaching, but then still retracting and repeating this like 3 times until finally connecting to extruder.
What to do next
Support is really slow with responding and their latest update suggestion was open a glass and cut inside ptfe tube a few cm, which I was already executed by the time I got their response.
Not sure how to solve this now
Possible failing part
These are a parts which could be failing:
First AMS port gears/motor. Highly Unlikely, as same is with all ports
AMS hub assembly. I don’t know I did a full disassembly and a cleanup as support initially suggested following this guide: Disassembly and Cleaning of the AMS 2 Pro Internal Hub | Bambu Lab Wiki but I did not find anything stuck inside and it was quite clean. I don’t know how to stress test this part so I would rate this as possible
Buffer. Again disassembled for cleaning, but there was nothing to clean. Not sure how to test this one, but support reported, that from the logs it looks like normally functioning buffer. So probably unlikely
Head extruder. This one was not yet disassembled or cleaned, but I can push filament through it manually (when hotend is disconnected). I feel consistent resistance, but no stuck feeling. Not very likely, as for some load attempts filament does not even reach head. Should I still dissasemble and do a clean?
PTFE tubes? Manual loading now is way smoother, but still having some small resistance when inside. So posible, but I doubt now
3rd party filament? Posible, but all is started and regresed when I had original bambu filament. Now waiting for new batch of bambu one, but order got stuck in processing for 10th day now.
Hope p2s risers are compatible with x2d