Have a weight on hand. I use it when I have a stubborn spool. Usually take some of my magnets and throw them in until the spool is empty or I’m done. I don’t have to do this often.
Ok I found why it is jamming and unfortunately there is not much that Bambu can do for this except changing every AMS on the market.
Here is what happens.
Each slot in the AMS has a individual motor/gear kit assembly (where you insert the filament). Once the filament inserted, the motor will turn one way to push the filament to the print head or turn the other way to rewind the filament back to the spool.
THIS is where it gets complicated.
If you look at the bottom rubber roller where the spool rest, there is a ‘’small’’ gear just beside the rubber roller so…
When and only when the spool is rewinding (filament back to the spool), there is a special gear assembly that is pushed ‘’by gravity/friction’’ against the ‘’small’’ gear on the bottom rubber roller that will turn the spool for rewinding the filament.
THAT ‘’gravity/friction’’ gear assembly DOES NOT disengage when it’s time to feed back the filament to the print head THUS locking the bottom roller and making the spool hitting the top cover because it is not rolling When you move the spool by hand back and forth, you are releasing that ‘’gravity/friction’’gear assembly and freeing the spool to turn well.
My only solution is to change the gears for metal ones, adding weight and releasing immediately when reversing the process but that is on Bambi’s side.
That was a long one sorry. Lolll
you are a somewhat correct.
There is an internal hub that uses it’s own motor to push/pull filament from the AMS. The feeders feed filament to that hub. once there that motor does the majority of the heavy lifting.
It isn’t gravity that disengages the gears in the feeders, it’s the reverse motion of the motor within. When the feeder motion is reversed it is friction that pushes those gears out of the way. If you’ve ever replaced your feeders you know the pain of putting it back together and having those gears in the wrong place. They will lock up if they’re not within the internal stops that are built into the clear housing. This is because the friction moves them beyond or into the wrong spot.
The feeders (first stage feeders) have enough pull to stage the filament within it’s slot. Once that slot is needed those feeders pull filament down to the internal hub, and it takes over. You will still see gears turning within the feeders though. It’s just reversed on the way back, and friction moves the gears you’ve mentioned out of the way.
I’m not discounting yours could be assembled incorrectly, but it’s unlikely. Could be debris that has fouled it, who knows.
The problem is the low viscosity of the lubricant on the pivots and gears that keeps it from dropping, not release the mechanism from rewinding the filament to sending it back to the print head. Adding some filament dust from grinding extruder motion to it sure does not help.
Remove the feeder and blow it out.
I have nearly 10,000 hours on my AMS, I haven’t had this issue. Not saying you aren’t, just trying to think of anything that could cause this on all 4 slots.
Take this with a grain of salt, these are the issues I’ve had. Maybe one of them will spark an idea.
Internal hub PTFE retainer broken.
Worn gear on the extruder like wheel in the hub.
Replaced all feeders as an overhaul, but had one where the gear had broken a tooth. That was my fault.
Of course worn PTFE.
Cables replaced on overhaul but I don’t think they ever gave any problem.
I had one feed issue with a feeder, but I honestly can’t remember. Replacing just the feeder funnel fixed it. Could have been dirty gear but I really don’t remember.
Every 1000 hours blow it out and clean. I’ve never replaced any grease or lubricant within the AMS.
I had issue like you’ve reported but it was a filament clip that stopped the spool from spinning. Aggravated me because of course it followed the spool but wasn’t obvious at first. An inside the spool type clip.
I may suggest as well make sure the cables are connected securely.
Wish I could offer more.
My “Skip and Jump Fix Version 2” does not seem to resolve this AMS roller locking up issue.
On a 9hr print with my version 2 fix the roller has locked Twice.
Came accross this on Makerworld;
There are three gears splined to a shaft in the feeder, and the gears can jump a spline. THIS COULD BE THE LOCKING SOURCE.
Both my AMS and AMS 2 where doing this behaviour from the very first hours of use, BRAND SPANKING NEW! Lol
I’ve watched this very closely for a good 2 hours and I still believe that the dissengaging of the bottom gear set turning the rubber roller gear is at fault and should be addressed by BambuLab.
Yours is probably working good because of the lack of thick grease missing? Maybe that would be the solution… to remove that grease that I find unnecessary anyway since nylon is slippery and resistant in itself and attracts plastic particules.
Couldn’t tell you really why mine is working well. The only time mine lock, is sometimes when loading a spool into it I can’t spin it. I’m sure you’ve seen that as well. It’s fine once the ams takes the filament.
So I’ve been having this issue since new. BL is no help as the issue is intermittent and I can’t get a reliable consistent video to them. But what I’ve noticed is that spools that deplete beyond half way are more prone to this happening. Both plastic and cardboard spools. I eventually thought it was a weight issue so I added a chunk of 2-1/8” thick steel bar cut to 1.5” thick. Giving me a weight of just over 1 pound. I slid it into the center of the spool and I’m telling you 97% of my issues went away. It actually just started acting up again momentarily. So I lubed the swing gears inside the first stage feeder and have t had a problem. When I first got it there was so much grease caked on those swing gears and shafts nothing would move. I peeled it all apart cleaned and “oiled” the shafts and gears and things have been way better all around. Hops some of this helps. It really started to seem like a “weight” and “load angle” of the filament to me. I have not found a way to get the filament off of a low spool and raise up the filament so it drops straighter into the feeder funnel.
Do I need to take the whole AMS apart to clean and lube these feeder gears???
Yes. Follow the wiki and be aware of all the wires. They all only go in one spot it’s pretty simple. Took me like an hour and a bit.
Please continue to provide feedback on whether this cleaning and lubing, solves the roller lock up.
Not looking forward to disassembling my two AMS
i had this issue with a brand new AMS 2 PRO from day 1. I found that moving the AMS off of the top of the printer helped. All 4 motors will get stuck no matter what spool/brand i put in there. I thought maybe the shaky prints could be causing the gears to skip and lock up. Like really lock up where you have to rotate the spool up and then back down again by hand to get unstuck. Did not seem to matter which slot. they all had the same issue. The table i have it on shakes a bit during prints.
right now i have the AMS resting on top of a large room air filter off to the left of the printer on the same table. it is at a similar height as the PTFE insert but maybe a few inches lower. If this continues to work i will likely mount the AMS to the wall for maximum stability. My work bench is a little shaky even without the printer 
I have changed to all Bambu refill spools and have not had a spool lock up in two weeks. Spools still jump when they get light.
I observed something yesterday. Nearly empty Bambu Lab High Temp spool was jumping like crazy at start of a print. Four or five jumps and then smooth after that. I believe that was a stuck roller and the printer managing to unstick the roller. Maybe I can use this information for a fix??? Why only on a light spool???
I here to join the Gear-Lock-Up Gang. I have 1 new AMS 2 Pro and 2 new AMS-HTs, all of which are locking up since day one. Regardless of the AMSbeing placed on the printer or on the table, full spool or low spool, Bambu or 3rd party, they lock up. I got so frustrated during one job, I pulled the spool from the AMS and relocated it on the external side spool holder.
It appears that the gear for Forward and Reverse is not always disengaging when switching from a retraction mode to a feed due to its speed and tension from momentum at the end of the retraction. When going forward during a normal print cycle…I have no clue.
This is my first 3D printer, and I’ll be honest, I’m not impressed with the QC of Bambu’s AMS. And if the AMS is going to remain this disfunctional, it seriously defeats the purpose of an H2C.
This weekend, I plan on taking my AMS apart and look for a solution. I hope somebody comes up with a solution because I have to stop writing this post 6 times to reset the AMS 2 with a full spool.
What type/brand spool are you having issues with? Cardboard, Bambu Labs, Sunlu ???
I am working on two different fixes, see
There is an interesting facebook short thats shows a reason for them appearing to lock and its in the design of the rollers internal structure = = = but i dont recall which model it was , bambu/anycubic or the integrity of the post/er but it does make sense when you compare it to the top of the feeders wearing
This as been happening to me ALL the time in the last few months. I’m constantly fighting for this thing to take the spool in and I’ve changed nearly ever part I think could have caused the issue. Extruder, hotend, PTFE tubes and recently the AMS feeder sensors. It’s still playing up. I swear it’s their firmware that’s done it.
My opinion is that it is caused by the amount of traction between the spool and the driving roller (Front).
When the filament remaining is light (smaller diameter), the AMS retracts faster then the filament is returned by the prefeeder. This creates a condition where the filament pulls the spool up. (Think of a man climbing a mountain face with a rope). If the AMS stops with this tension against the retraction gears, the front roller is frozen and can not feed.