I’ve got an H2S and AMS 2 Pro combo with about 2000 hours on them so far. The AMS 2 Pro started having AMS roller/feeding issues recently. I filed a trouble ticket with Bambu, and they were nice enough to send me 2 of the feeder units for replacements after quite a bit of back and forth. But now it’s happening to the other two. Before I reach back out to Bambu I thought I’d pass this by the community to see if anyone else has seen this issue?
Basically after a little bit of a spool sitting still, the roller motors seems to get “sticky” or have a higher than normal resistance to rolling, but only briefly. I’ve done my best to keep this unit clean, and even have taken it apart to deep clean it. But something is causing the motors and rollers attached to the motors to be just a little troublesome to move right as filament starts to feed into the printer for a new print or color change. The spool bounces around in the AMS as this occurs as the filament is pulled into the feeder, but the spool won’t roll.
It’s kind of difficult to properly describe what’s happening, but after playing with the AMS while this is occurring, the issue “feels” like the motor rolling the spool rollers underneath is resisting. The resistance feels magnetic, not like dirt getting in the way. Like the motor is breaking the rolling action just a bit. And, wiggling the spool, or rolling it slightly backwards, and it immediately comes loose and rolls perfectly. It’s not the filament tractor, as the filament feeds just fine. It occurs mainly with spools that are almost empty, as it seems the heavier spools will give it enough weight down on the roller to make the motor give way and allow it to roll. It will cause prints to stop with a filament feeding error if I’m not there to take action to help it along. It’s almost like a firmware issue causing the motor to resist turning the rollers initially.
Here’s an unlisted YouTube video I put up to demonstrate this issue. You can see that it does roll, but very slowly as the resistance digs into the spool, and the spool pulls upwards due to the resistance. At the end you can see me wiggling the spool and then it rolls like nothing’s wrong. I can also manually roll the spool backwards a bit and then it rolls forward freely. I can feel the resistance from the motor if I attempt to roll a spool forward while this is happening, or the spool has sat idle for a short while. https://youtube.com/shorts/-jqOONIMt5A?feature=share
Anyone else seen this before and know what it might be? I hate to keep bugging Bambu on this if it’s a simple fix.
Im curious about those “guides”. I notice the eyelet is flexing/moving towards the spool when it’s happening. Have you tried without them installed once the issue starts? Is it possible filament residue is getting in the feed units after a while from the guides?
I have not had this issue on any of my AMS 2s but I also have not done a lot of drying in them over 45-55c if I have enough rolls of PLA to dry. I use the HTs mainly to dry filament as needed and I have noticed some bouncing and other things on them lately but I dry things at max temp so they do get toasty. I’m only around 1200 hours on them though.
Bambu was interested in them too and asked me to remove them for testing. The PTFE tube moves due to the spool resisting rolling as the filament is drawn normally into the feeding gear. I removed the guides and the problem continued. There really doesn’t seem to be anything physical that I can see or find keeping the rollers from moving freely at first. I also have dried only PLA/PETG in my AMS 2 Pro. The problem came up around the 1800th hour.
Is it the rollers or the feed unit you replaced? Those bearings on the rollers might be gunking up. Its late, but I “think” the AMS 2 has the same good luck finding it if they fly off bearings on the end of the rollers.
Edit: Sorry I see you did replace them. My initial gut was those annoying bearings in my iRobots getting crappy and I got a little tunnel vision.
I am having same or similar problem. Sometimes I get an error that the filament is stuck and it is the rollers seem to be locked and it is trying to pull the roll of filament over the rollers. I have to pick up the spool and let out some filament and then roll back and forth on the rollers, and it works. Not sure what is causing the rollers to lock up.
Thank you! Seriously we are not crazy. I think it’s a firmware issue with the AMS causing the roller motor to forget to allow the spool to turn. If you move the spool ever so slightly backwards it rolls forward with no effort. I just got 2 new AMS Pro 2 units for my X2D and they both show the same issue. Bambu needs to put some more effort into this issue.
Thanks for the input. However, the issue is familiar to me in that the motors for the feeder seem to be the reason. Roll the spool backwards a bit and then they move forwards with no issue. I think it’s a capacitive issue with current holding the motors tighter than they should be. Bambu unfortunately did not engineer the current feed into the motors well enough to expect current leakage into the motors after a small amount of time causing the motors to get tight and stop turning enough to feed filament the proper direction.
Nope no solution yet. Bambu is sending me a replacement motor, going to install it in the next week or two, we’ll see. I can still open the AMS and find a spool frozen from time to time. Very frustrating.
Wrong, it’s because the motors for spinning the spool are locking up. I’m in discussion with Bambu on this, and they are working on it. No idea when it will get fixed, but probably not in existing AMS units.
I don’t think it’s a gear, but might be, that’s a good thing to consider. I’m not sure because I was able to demonstrate this issue on a brand new out of the box AMS 2 Pro unit. Unless Bambu has a serious design flaw in their hardware here…
The motors/gears lock up due to resistance ,from both pulling from the roll to pushing via the ptf, i recently cut my ptf tubes to be shorter with less kinks and bends in them to help prevent this ,after getting constant error messages telling me that it was a problem (hms errors) , now its just one short straight line ,error messages have gone , (also includes a 4 in one connection) will be trying the same with the second one shortly , to see if it helps with a roll of less than 100gs , very intermittent currently with only an occasional snag , (h2s a 2 ams) , i also looked into moisture content and decided to add those silica models to see if that would help.
Nope, not PTF Tubes in this case. The reason the spool kicks up is that the filament is being pulled in just fine, the spool won’t roll due to motor resistance (or gear resistance if some are right…)
There is no filament resistance, only spool rolling resistance.
Not to say you didn’t see PTF tube issues, and fixed those. Those types of issues are very common.
In my instance the motor keeps pulling and the gears appear to lock up (the one on the roller bar), you can both see and hear it trying to pull and its generally spools that have little filament on them , it doesnt occur every time it loads or changes filament , but it does appear that it happens mostly when the filament is being pulled from the left hand side of the gear on the roller bar, a quick fix is to simply lift and seat it again
That is awesome information. I’ll dig deeper into my AMS units. I wonder if this is occurring, maybe a little grease in the right area of the gears might fix?
Also, I say “Lockup”, as you do. But it’s more of a very tight limit on movement. Do you experience the same?
I also find that bumping the spool when this occurs (technically rolling it backwards ever so slightly) causes the issue to release. Issue is if I’m not near the printer, it holds up printing sometimes until I can get to it, leaving the printer in limbo for hours at times. Not exactly a great situation.
Thanks for your input, hopefully together we and others in the community can find a real fix and not just a bandaid.
Roll them or lift them it achieves the same outcome, i just checked mine which are not in use and are switched of with rolls in them (lazy i know) all the slots are locked until i rotate or lift them, generally backwards first if rolled .
I’ve had this too. Loosen the filament on the spool up (manually pick up the spool and de-spool / loosen up the filament and put the spool back) and it works again and can finish the print. Every now and then it can’t feed the filament all the way in to the nozzle, especially during simple multi-color prints. I don’t know if that is related or a different issue.
I think the issue with filament feed issue is that it took too long to retract, or too much effort/tight spool, the filament and the filament melted/stretched a bit and then it gets caught either in the buffer (wish it was on the outside of the H2) or as it goes in past the filament sensor but can get in the the hot tube due that melting/misshapen filament end.
There was a person who researched this roller sticking issue, and he claimed it was caused by the diameter of the filament left on the spool. He played around with respooling to large diameter spools. Most people have good luck with adding weight. My fix has been 100% solid for me.