Have AMS use remaining filament in bowden tube when out of filament?

Bambu Lab AMS General discussions
1

Hi, is there a way to have the AMS use the remaining filament in the bowden tube when it detects that it is out of filament?

The printer should know where the filament is in the tube already because of the sensor positions.
There’s still a lot of useable filament that’s purged out before the next available AMS slot can be switched to.

2

If the printer is using filament, it will use all of it until it runs out before requesting a new spool to replace the one in the existing slot or moving to another spool that matches the one it was using and you enabled auto run out.

If the printer stops using a filament that is partially in a tube and no longer on a spool, it will extrude it out completely and dispose of it as poop to clear the tube ready for the next filament.

3

Sadly not, it will waste all the filament when it has been through the AMS sensor and the print completes before the filament runs out.

The way the AMS is designed, doesn’t allow it to keep filament in the tube for using. From what I can tell, the AMS is designed to never have (except when you cancel the print) filament stuck in the tube when not printing. Makes sense, because if the filament is still in the bowden tube, you can’t remove it from the AMS to use another one. I think there are some more reasons for this design:

  • have the same conditions every time a print starts
  • when the printer looses power, it must not detect what filament is still in the bowden tube (like color, material)
  • I think filament stuck in the bowden tube to the printer, will interfere with the initial “rolling around of the filament in the AMS”/reading of the rfid. That thing it does every time the AMS starts, or you press the refresh filament button in the slicer. Seems like it unwinds the filament, until it reaches the buffer (that thing with the spring) at the back of the printer.

Note that these are just guesses and observations, maybe I am totally wrong. What I haven’t checked is how the printer behaves, when you have cancelled a print (where filament is stuck in the tube).

I had the same question that you posed here, which is why I spent some time thinking about it, and the above are my thoughts on why that is not going to happen. Some other things:

  • I don’t think it wastes that much filament, maybe 10g at most?
  • The AMS wastes quite a bit of filament, even when you are always printing with the same spool/color/brand, because it will always cut/purge the filament after/before each print
  • I mostly try to not do small prints with small amounts of remaining filament (to prevent this unnecessary waste), I mostly use them up for larger things or fill the entire plate with multiple copies of the smaller thing.
4

@luro02 @MalcTheOracle Ok, that makes sense that Bambu doesn’t want to deal with waiting for the filament to trigger the runout sensor at the printhead due to complexity.

But this actually leads to my actual issue which made this question:

When the spool is tangled, is there a way to unload the existing filament all the way back to the AMS so I can fix the tangle AND reuse all the filament? I had a tangle that the AMS detected and I saw the tangle point.

Normally I would release the extruder gear on my Ultimaker printer and pull all the filament back > untangle > put the filament back through to the printhead > resume. However I don’t see retracting the filament out from the printhead as an option.

So I cut the filament at the AMS, untangled it, and put the new tip in the AMS hole. But as the printer resumed printing, the AMS motor that assists the filament moves but this is not the same AMS loader motor for the AMS slot. So the old filament was pulled to the printhead as usual but the new tip was not pulled along. Later on, the filament was detected to be “empty” at the printhead and all the rest was purged (which was my original post question).

How can I resolve a tangle in this situation without the filament purging after 10 minutes of printing after resume? I’d like to resolve the tangle and walk away from it until there is a new tangle or the print is done.

5

You don’t say if you have an AMS or an AMS Lite.

AMS lite is easier as you can remove the specific PTFE tube from the hot end and cut it. Removing it back to the spool.

If you can get to the head of the P or X series printer and cut the filament you can pull it back.

On both you can press the cutter in on the head and that should allow you to pull it back out.

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6

I have the AMS with X1C and not the lite.

So you mean I should:

  1. Manually press the cutter lever on the left side of the printhead.
  2. Pull the filament out
  3. Untangle/etc
  4. Push the filament back in all the way to the printhead

Do you know if the filament cutter is before or after the runout sensor in the printhead?

Do I need to maintain constant pressure on the filament until it passes the filament runout sensor in the printhead (when it is gripped by the printhead)?

7

Yes, you can manually press that level, it is exactly what the printer does when it presses it.

Follow the rest of the instructions.

I do not know if the sensor is before or after.

This is where you need some trial and error.

When getting a tangle/jam on my P series, it usually returns the filament back to me to deal with, when I have fixed the tangle or jam, I push some filament back into the AMS it takes it and tries to extrude it from the hit end and all continues.

On the A series, the same happens.

I have had a jam on that where part of the filament gets stuck in the head and new filament can’t get through at all. I have had to remove the hot-end to let the filament drop out before I could start printing again. The print job was lost though.

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8

Just a small addition: If I observed that right, the printer always heats up the nozzle before cutting. I don’t understand why, but probably there is a reason, so I would make sure the nozzle is hot before pressing the lever.