my first time trying auto refill, but when it came time to change it stated it could not pull back filament, please clear blockage to continue and after taking the feed tube out of the head there was about 15cm of filament sitting in there, how can it pull back when it is no longer connected to the AMS? I would have thought it should just purge as much as it can until the filament was past the feed drive in the head, then push the new filament down from the AMS until it engages. Why did it cut it off?
During a normal filament change cycle the printer will cut the filament at the head so it then can be pulled back to the spool via the AMS to change to another color.
During a filament runout situation, the filament will be pulled off the spool and is pulled via the extruder until the end reaches the filament runout sensor. This will trigger the AMS to load in the next filament to continue printing (with the same filament).
The problem arises when the filament has been pulled from the spool in the AMS but the program calls for a filament change to a different color. The AMS can’t pull the filament that is in the tube back and will error out.
In short, auto refill works well when you are printing one color, not when you are printing many colors.
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I had two identical spools in the AMS, no colour change requested. The popup on the screen said it detected the runout, I don’t know why it got confused.
Unfortunately the system isn’t perfect and there are instances it can’t recover from. A section of filament stuck in the PTFE tube seems to be one of these.
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The bambu actually resolves this by purging the old filament if it is too short to withdraw it. Mine did it the other day, it sat there purging several times. At first I thought it had gone crazy, then I realized what it was doing.
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Oh that’s good to know, I haven’t encountered this.
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Ths is exactly what it does, yours must have errored out somehow. Filament got stuck somehow, etc. Usually with me the filament is attached too strongly to the roll and the AMS can’t pull it off the roll. (This is probabyl beecause I use too much Sunlu filament)
It had me scratching my head when it happened to me, makes sense though as there would be massive issues trying to feed a stub back through and have it curl inside the AMS (actually it’d probably get stuck in the feeder). Edit, well derr once it passed the AMS motor it’s on its own and can’t be retracted…
I’m encountering this issue still.
I use Sunlu PETG filament and it will release the remaining once it got pulled at the end. Somehow Bambu Lab software designed to sense the filament condition and try to pull back which cause the error.
Does anyone solve the issue?
It will and does purge if there is not enough to pull back - though i find filament often gets stuck on the roll as the ends are too tight, or can break in the AMS, the second case is one way that can cause the error you have experienced.