The whole thing was working great for months, then suddenly it stopped feeding and generated the “jammed” message. In watching it try to feed it always stops at the same location as shown in this video:
The machine feeds and prints fine when I use a single roll and load it.
I’ve tried
Bambu brand PLA
position 1 and position 2 of the AMS
Can you please help me diagnose and fix this issue?
Double check that the filament isn’t caught on the side of the spool or looped under.
I’ve tried different reels, one of which I later loaded manually and have been using, so I’m sure there are no jams at the reel level. Plus where it stops is midway through a PTFE tube and it’s exactly the same place every time.
This leads me to believe that it feeds it through the filament buffer and is expecting some signal from the buffer which it isn’t getting.
Now I admit that I don’t know exactly what the buffer does but in watching it during this process there is no physical movement within the mechanism as the filament passes through.
Either that or somehow the feed-before-failure-distance setting (if there is such a thing) got changed to a much too low value.
Thank you,
I have had nothing but problem after problem with this very thing. I have reported this time and time again. I can’t seem to get the AMS to maintain a consistent resolution and get error after error only to have them say to me today. “Seems like the AMS is having trouble connecting.” Yeah, duh! Said this from the beginning. LOL seriously!!! It takes pulling teeth to get these people to understand what I have been saying since I got this machine. If I wanted a single filament machine. I would have saved lots of moola on that. But hey, let’s just keep stringing me a long. So annoying.
I couldn’t really see where the filment is but that is a pretty tight curve at the tubing coupler. Could the filament be snagging some of the guts of the coupler. You’d be surprised at what is inside those couplers to lock the filament.
So the point at which it stops there is no snag. I ran some filament through it manually:
and it’s smooth as silk.
Can someone explain to me, technically, what this thing does? I know it’s got a Hall sensor which I assume reads the movement against the sprung slider, but in my case the fllament moves through and nothing internal to the device moves at all.
Bottom line it’s absolutely not a path problem.
I can order a replacement of this assembly I believe, but I’d like to know how to determine that it’s failed before I do. The PCB looks fine.
Thank you,
There should be some mechanism like the blue thing inside the moving part (2) to pinch the filament. So that that part (2) would move along with filament when pushing filament from left to right.
The part (2) has a magnet that triggers a hall sensor when it is at end of its travel. This to tell the AMS that the AMS doesn’t need to push filament in anymore, relax the assist motor until the spring moves part (2) all the way to the left again. That why this is called “AMS buffer”
Since the grippy mechanism (in blue) allows filament to slip, it’d be under subject of wear very quickly if filament in used is abrasive type
As far as your question about the buffer, if you haven’t used it much, the wiki is very handy and has lots of information. The buffer acts as a sort of shock absorber for when filament is being fed or retracted. If the spring and slide inside the buffer move freely it is probably okay
Passing filament through the device on the table like that has not a good indicator because it is not reflective of the curves and bends when every thing is mounted.
When the PTFE tube is mounted to the printer at one end and the AMS at the other end, the AMS pushes it from the AMS until the extruder grabs it.
If you force tight radius bends in the PTFE tubing, the filament is going to ride against inner wall of the PTFE but against the outside of the curve. Tight radiuses will cause the tubing to wear out faster because the filament, being stiff will ride against the outside of the curve. Tighter curve more pressure and rubbing of filament against tubing.
The still of your YouTube video, it is easy for me to imagine that the filament is making a tight turn and potentially can snag the coupler internals.
You want the run in to the coupler to be straight.
Try running the PTFE so it is straight and runs out the edge of the picture on the right side and then goes under the the manual spool hanger.
Here are some pics of how you want the tubing as it approaches the couple going into the printer body. I got those from a Google search and the bottom picture, I would have a longer run of tubing between the buffer and coupler so the run to the couple straight like the top picture.
Buy the tubing in the longest single piece you can buy so you can cut it to fit and not have tight radii anywhere.
Thank you @simon14, I think this is the root of the issue - there is no resistance.
I’ll tear that thing apart and see if I can figure out how it worked and (hah hah) 3D print a replacement part.
Probably I’ll go ahead and order a replacment module and take the opportunity to swap out all the tubing (which I think I can get on McMaster).
I’ll post the results here.
Feels like there’s probably a better design than something that drags against the filament. Last night when I wasn’t sleeping I thought maybe just a loop and a lever switch would do the job. Or a standard computer mouse module might have enough resolution to detect movement of the filament. Feels like an upgrade opportunity.
Anyway, thanks for your guidance.
replaced the filament buffer and exactly the same behavior. It does not move the spring assembly at all.
@Simon14 The new buffer exhibited exactly the same behavior as the old buffer when tested on the bench, no resistance, no spring movement, nothing changes at all as the filament moves through the buffer. Same in situ.
@Wsquared58 To test your theory of the bend radius being too tight I simply removed the other end of the tube from the machine and let it hang loose. Exactly the same behavior.
I’ve uploaded a video here of the behavior
I know it’s a bit of an imposition but if someone cold upload a video of how it’s supposed to look when it loads that would be super helpful
Thank you,
What HMS fault code are you getting?
I think it is probably close to impossible to see the buffer in action because it is tied to insertion and retraction of filament. When the machine is idle the buffer is also idle
Have you taken a crack at this, in the Wiki?
Board doesn’t necessarily need replacement but might be worth taking apart and reassembling.
Filament Buffer disassembly & reassembly
I have the same problem, but only with a specific spool. The filament is only pushed up to just before the extruder.
Were you able to solve your problem?
Well I did by watching the video figure out how the filament buffer actually works. It has nothing to do with the filament itself, it has to do with the tubes. When the filament is locked at the AMS end but is being drawn at the extrusion head end the tubes will get pulled towards each-other and that is how the buffer signals the AMS to feed.
Kinda ingenious actually.
But has nothing to do with my problem.
My next test will be to disconnect the tube from the filament buffer and see how far the AMS feeds it before giving up (or if it feeds it forever). If it’s the case that it feeds it the right distance or forever then there is a drag problem in the tube between the AMS and the buffer.
If not then I’m back to the idea that a setting got corrupted which, unfortunately, is somewhere in the AMS firmware.
@Orca200 is there something special about the spool that fails? Like is it glass filled or CF filled or something that would present more drag in the tubes?
OP did you ever resolve this? I have the exact same issue right now. Filament stops mid way in the PTFE bend towards the blue / black coupler
I am not going to read this whole thread but allow me to make a suggestion few bother to look at.
It is possible that your PTFE tubes are worn in one or more spots from the feeder to the print head.
There are 4 internal tubes in the AMS, one from the AMS to the hub, one from the hub to the coupler, one from the coupler to the print head. If you’ve never changed them the ID will wear and cause feeding issues.
Another issue could be a broken piece in the coupler. You wouldn’t see it without taking the tube out of the end and looking.
Lastly, and doubtful if this just started, but less so if you’ve never changed the tubing, the bend could be too sharp an angle.
You can pull the PTFE and look carefully at the end. If the ID (inner diameter) looks misshapen (should be a circle, near perfect) then it’s a good chance that’s the culprit. If you’ve never changed the tubing than that wear will be within nearly all tubes.
In my case the filament stops inside the tube after passing through the filament buffer. I unplugged the tube that goes into the printer to investigate.
The filament stops about 2 cm after coming out of the tube. I can hear the motor trying to push it, but it cannot move forward. If I gently pull the filament by hand a little bit, it suddenly starts feeding normally.
My temporary workaround is this: when the filament reaches the end of the tube and stops, I pull it slightly by hand and immediately insert it into the next tube leading into the printer and reconnect it.
This is not a real fix, just a workaround. After the filament passes the extruder once, it feeds normally afterward.
No I never did. Unfortunately I went back to manual reel.
I still believe it’s a firmware issue, that the overfeed distance failsafe is kicking too early (if there is such a thing).
I will, for science, hook it all up again and see if the AMS gets a firmware update and maybe they quietly fixed it.
Indeed the firmware did update, but nothing changed.
In my case the motor stops. It’s not still trying to push. It moves maybe 5cm out of the filament buffer then rewinds and retries. There’s no point in trying to pull it since the motor isn’t trying to push it.
I would just try cleaning the tube. Make sure your AMS is working properly and your toolhead gear is spinning
It’s not the tube. Remember, the motor stops running.
AI says that it’s probably the feeder motor in the base of the AMS, which counts how much filament has passed using a Hall sensor, but if the feed wheel s gummed up than the count will be off due to slippage. Turns out it doesn’t measure actual filament movement, like with an encoded idler, but it measures how many turns the feed motor has made. so if the Filament is slipping on the feed motor gear that would explain it. But that woudn’t explain why it always stops at exactly the same place regardless of the filament I’m feeding.
It’s not the individual feeders because if it was it would stop at different positions assuming they showed different wear (which they would, first feeder showing the most by far)
In the end, since the new AMS2 isn’t significantly expensive it doesn’t make sense for me to tear the old one apart and try to fix it. I’ll just call this an upgrade opportunity.
