How I (Sometimes) Clear a Jam in the Bambu AMS

While I was running a prototype print today, to test an update to my Bento Style recirculating filter, I had a jam occur inside the AMS, after some wet PLA snapped as I was unloading the spool.  When there is a broken bit of material inside the AMS, it can be a pain to remove, sometimes requiring partial disassembly of the AMS or even the AMS internal hub.  There is a "trick" that I recently found to clear AMS jams though, and if it works, it can save a good bit of time.  The method I've been able to use is described below, but this method is not the recommended way to clear filament jams in the AMS, and therefore I have to add that this information is for educational purposes only, and if you follow what I did below, you do so at your own risk.  Additionally, this only works if the jam is inside the AMS, it will not work if the jam is outside the AMS or in the hotend. Also please use eye protection when working on printers, read the manual, don't eat the silica gel packets, etc...

This is the method I've used to clear filament jams inside the AMS, and sometimes it even works:

1. I remove the spool where the break occurred, and wait for the printer to stop trying to load/unload the filament.  There may be a red light on the feeder.  There may be an error message as well. 
2. I then disconnect the Bowden tube at the back of the AMS (this may require partly removing one of the center spools).  If another spool needs to be removed to access the disconnect, I avoid pulling the filament out for that spool.
3. Next I cut off a 16" length of filament, preferably PETG, but definitely not the same wet spaghetti PLA that broke in the first place.  The filament must be good material which can flex without cracking. 
4. I then install a good spool in the slot where the break occurred (not the wet spool), and then feed the filament in as far as it will go through the feeder tube for the slot, until it stops (just until it stops).
5. I next insert the length of good filament (the 16" section) into the back of the AMS where the Bowden was removed, until it stops, keeping some light pressure on it.  It's important to keep fingers far enough away from where the filament goes into the AMS, since the filament will get pulled in on the next step.  A short length of Bowden tube could also be attached to the AMS rear filament inlet to assist with this, but I've done it without needing a tube.
6. From the printer screen, I then attempt to unload the filament on the position where the break occurred.  While the printer is unloading, I keep light pressure on the filament that is fed into the rear of the AMS.  Making sure to keep fingers well away from the rear filament inlet on the AMS, as the filament is pulled into the AMS.
7. Once the AMS starts to draw in the 16" length of filament from the rear of the AMS, I let go of the filament being fed into the AMS.  The rest of the process is hands off.  Any weird noises at this point, I'd probably power off the printer and clear the jam the "correct" way.
8. I allow the filament attached to the good spool, which was fed all the way into the AMS slot to be pushed out.  I usually will try and grab the loose end as it gets ejected from the feeder, so it does not end up tangled.  Following it, should be the broken piece, which will then be followed by the length of good filament (about 16") which was fed in from the back of the AMS.  
9. Once the 16" piece of good filament is pushed out of the AMS (through the front feeder for the slot), the clog should be cleared (if the broken piece was previously ejected from the feeder in the prior step).
10. Finally, I will dry the spool that had the break, and then it can be reloaded into the same slot. It should be possible to continue printing at that point using the dry filament.

The TL;DR of this is that I use a section of filament from both sides of the break, which are pushed against the broken section of filament inside the AMS.  The AMS can then (potentially) unload the filament, and move the broken piece out when the internal hub and the feeder drive against the good sections of filament that "sandwich" the break.  If it works, the broken part will be driven out through the feeder, along with the good sections of filament used to drive the break though the AMS.

If that does not work, then the AMS will need to be disassembled to clear the jam.  It's not a bad idea to do that anyway, since it allows the internal Bowden tubes to be inspected for wear, and if the clog is inside the hub, the hub can also be cleaned out (it collects filament dust over time).  As with any off label work on a printer, I always try and be ready to shut off the printer, if things start making weird noises.  It hasn't happened yet, but a "plan B" is always a good idea.  

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