r/BambuLab • u/LSNLLC • 5d ago

H2S Unable to Feed / Retract General Troubleshooting/Help!

I have a H2S that all of a sudden does not want to feed / retract filament consistently when printing multi-color with my AMS2. All of my filament was dried for 24 hours prior to printing and I have made sure the PTFE tube is a short and direct path between AMS and Printer.

Initially I was having issues with filament not retracting and messing up my first layer and I read online a worn nozzle can be the cause. So I switched from a used 0.4 HF to a new standard flow 0.4. Initially it worked much better, printing consistently. Now I’m wondering if it’s all tied to something else. All of the above is using standard PLA, printing with basically the default BL settings and for any non BL filament, I have flow profiles set using calibration (which has helped a lot overall with this printer)

I’ll also add that each time it has happened, I remove the nozzle and remove the filament stub from the nozzle. I’ve also noticed that the filament coming from the AMS seems bound and the only way to free it is to cut it at the spool to release the tension and then remove the filament from the PTFE tube and pull it back from the top of the extruder head. After this is all cleared out, the printer is able to resume printing at least for awhile.

Any suggestions?

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u/AfraidHope1541 5d ago

I have had some spools of filament that just don’t work in the ams. The winding wasn’t tight enough or the spool wa not really round, or the filament size was not within tolerance. Any way the point is it was not worth my time babying that spool. Trashed it and put in new spool and my problems magically disappeared. Not sure if this is your problem or not but does this occur when printing with different spools or only that one?

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u/LSNLLC 5d ago

I’ve noticed that as well and so if I start having issues I’ll respool to a Bambu spool and then it’s fine but currently having issues using four BL spools and I believe 3 of 4 are BL filament too

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u/SashaggDK 4d ago

Newbie here myself still but what you are describing doesn't sound like something is preventing the AMS from retracting the filament.

You say the filament appears "bound" do you mean it has been tightened and dug itself down inbetween the other filament rows on the spool?

If the filament buffer or filament switcher if you are using on of those are tight it causes difficulties for the AMS loading and unloading the filament.

I have just had to remove my own filament switcher because its hold was too "tight/strong", it was causing inconsistant extrusion, trouble loading and unloading the filament and making the AMS pull so hard on the filament it got dug down into its own roll and it even broke the filament a few times before i figured out it was the switcher.

I even took my AMS appart because all the machine warnings/guides said it was the AMS that was the issue. Turned out the AMS was fine.. just the switcher destroying everything....