AMS Slot 1 Active When Printer is Idle

Has anyone noticed the AMS feeding and retracting filament when the printer is idle?

I have a roll of generic ABS in slot 1. It did it enough times for the filament to break off the roll. Luckily I was able to get the tiny stub out of the hole the filament feeds into. I haven’t timed it yet but I would estimate it doing it every 5 minutes or so.

Is there a way to make it stop doing that?


Hi Lyndondr,

My best guess is the funnel filament sensor in the AMS slot 1 is give open and close signals at times.

AMS Feeding Funnel

They have two versions of sensors: the check ball type and the new micro switch type.

You can use a multimeter to check the switch signal or can also swap the filament sensor to slot 2 if the problems move you know 100% the filament sensor is causing the problem.

Is your AMS the current firmware ?

Keep us updated :v:

I haven’t checked the sensor, the printer was shipped the first week of April.

The firmware is current.

I’ve since put a roll in slot 1 that has an RFID tag and it did it too.

At this point I don’t think it is the sensor, it seems to regular for something that is failing. It would seem more like the software is polling the printer. I’ll sometimes leave multiple computers on with the Device tab open monitoring the printer. I’m thinking through this as I type, the laptop I use by the printer will frequently drop the wifi connection and maybe when the software reconnects it polls the AMS causing it to roll some filament in and out.

I’ll do some more monitoring and testing and see if I figure anything out.

Thanks for the reply, I did see it just a little bit after you sent it.

FYI. The filament detection sensor is what tells the AMS when filament is inserted into the funnel then it will load the filament it has another sensor for reading the filament type id.

You can also roll the AMS firmware back to see what happens but you are the only one I know of with this problem.

Put two rolls in slot 1 and 2 if slot one is only one doing it then I would swap the AMS first stage feeder to slot 2 with the wire harness to see if the problem moves to slot 2.

It’s possible you could have a bad AMS main board.

Open a support ticket just in case Bambu has seen this problem or not and they can get you a solution in the works.

Keep us updated and have a good one :v:

This happen for me too. No difference using Spools with or without RFID.
The first slot is feeding and retracing at short length once an hour.

I’ve found whenever a instance of Bambu Studio is started and connects to the printer it will cycle that first spool.
I have a laptop that will have intermittent wifi connections and each time it reconnects it cycles the #1 spool.

If you close all of your instances of Bambu Studio it should stop doing that if that is the cause your printer is cycling the spool.

This problem has started for me, just this morning. I printed something over night, all Bambu filament. Its slot 1, and it feeds half an inch or so and retracts. But for me, it’s every 60 seconds or so, so I’m worried it’s going to eventually wear something out.

I am currently transferring timelapse files from the printer, over ftp. And I also have Bambu studio open. I just closed the studio however, and it did stop moving. So I guess that’s it. I’d swear I’ve left it open most of the time, and never noticed this. Either way, I’m sure a bug exists, that could be fixed. For now, I’ll just close the studio.

Thanks for the info!

I have the same problem here, it happens every few minutes, which now broke the existing filament in Slot 1 three times.
Having the Slicer open or not does not seem to make much of a difference

Just noticed this problem as well. Printer was delivered Nov. 23. I’m guessing software related. Hopefully this will be fixed with an update.

Same here i am having ISP issues so the slicer is dropping connections after reading this this will make sence. i will be adding to my existing ticket and seeing what they have to say.

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Same on my side. I’ll try to close my BambuStudio and see if it fix that annoying reaction :hand_with_index_finger_and_thumb_crossed:. Got the printer two weeks ago and it’s been doing this since day one.

I noticed the same problem. Looks like periodic polling in slot 1.
I have Bambu PETG spoil there. Previously I had Bambu PLA and it was doing the same.

The issue is gone. I tested by closing BambuStudio and it stopped! :star_struck:

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