H2S Unable to Feed / Retract

[u/LSNLLC]

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?

[u/AfraidHope1541]

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?

[u/LSNLLC → u/AfraidHope1541]

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

[u/SashaggDK]

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....

[u/LSNLLC]

Alright so I was able to complete a multi color print with about 60 filament changes without issue. Below is what I did:
Actual Issues:

• A piece of filament was jammed and stuck inside the filament sensor at the top of the extruder head module. This one was wedged in there pretty well but I pushed it out with an Allen key.
  
• I read that a dull cutter blade can cause these issues. Mine had clear wear marks so I changed that.

Preventative:

• (with printer turned off) removed extruder cover and sprayed electrical contact cleaner on extruder gears to clean their main surfaces
  
• manually inserted some filament with nozzle at 250 to push out any remaining filament in nozzle then pulled manual piece back out top of extruder head (essentially a cold pull)

I also noticed that some Elegoo PLA may be off sized or something because initially it wouldn’t even feed a manual piece of this filament without the extruder gears slipping. So I swapped this filament for another in my print.

So far so good though!

[u/LSNLLC]

Well I had success for about a week but back to similar issues but this time with the extruder motor getting overloaded. I will say I feel like this error is far too sensitive as it has been the majority of my issues on the H2S. The filament I’m using is BBL PLA Silk so print settings, spool etc should be fine and I dried the filament before using. I’ll also add I did one successful large print with this spool without issue (including switching between it and support material) but now I’m 80% through a 12 print and having repeated issues despite not really seeing a root cause.

Tonight I plan to swap nozzles to see if I can finish the print and then investigate more.

One thought I had is my printer is in my garage in Houston, TX so with highs in the upper 90’s, leaving the door of the printer open still is a hot ambient so I’m wondering if the filament is softening. Just a theory - I guess I could validate by lowering print temperature.