AMS cannot retract if spools getting too light?

I have the problem with 2 spools now. There is not much filament left and at some point the AMS is not able to pull back the filament at the end because the spools do not have enough grip (because of the weight?) to actually pull. The spools are simply not rolling.

Workaround is to open the AMS and unroll a bit of the filament and then manually click unload and at that moment turn the spool manually until the filament is moving. Then it works fine again.

There is no problem with loading filament again later - just the unloading does seem to be a problem if the spools are too light. Any idea how to fix this permanently? It is not a problem with a single color print but I assume a lot of trouble when I start doing multicolor prints as I now have two spools which have this effect in there.

I’ve seen this issue happen once as well with on original Bambu spool that’s nearly empty. I presume the easiest solution is to add a weighted insert into the centre of the spool? I’ve successfully saved a multicolor print by doing this (do note that it was a third-party spool in this case, it didn’t quite fit properly). I’ve yet to design a proper part for it. maybe i will if i get around to it.

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I printed some very simple cylinders I filled with silica gel and inserted into the spools. The extra weights seems to have done the trick for me,

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The Silica gel is a genius idea! Can’t believe I didn’t think of that. Definitely going to use this.

in my experience its less of a weight problem and more of a gear ratio/angle problem. The middle of the spool doesn’t pull correctly out of the feed hole. it puts a massive amount of stress on the AMS rollers and feed hole, it cant be good for it.