I have a brand new AMS that appears to have issues with the AMS Active Support Shaft seizing up during feeding. From Bambu Wiki, the AMS Active Support Shaft is only driving (active) during unload phase and driven (passive) during loading/feeding phase. Does anyone have similar issues with a proper resolution?
I have seen suggestions to add weight to mitigate a similar issue, but that suggestion seems irrelevant here. The spool would continue to spin freely–regardless of the force or velocity in which the feeder motor is feeding filament–as long as the AMS Active Support Shaft continues to be free.
I have multiple Bambu printers with AMS units and have not had this issue in the past. This is my first one from BestBuy. Coincidently enough, I have seen two other people pick up Bambu AMS combos from BestBuy with the same exact issue…
I am still within my return window for another day.
I have tried slots 2,3,4 with same repeatable outcome as shown in my GIF. I did not swap the Active Support Shafts, I just tested a couple other slots.
I think that is just the common problem people report of the spool being too light, but I’m interested since you say only one of your AMS’s do it and I wonder if there is a production difference.
For weight people sometime use a C or D cell battery in the spool hole.
I have seen 100s of videos on YT with AMS over the years but never once saw anyone weigh it down. But I will give it a try tomorrow. If it works, it works .
Can you expand on why the Active Support Shaft seizes up due to light weight spool? Is there a weight activated mechanism within the AMS?
I have the same issue, what solved it every time for me is to turn the filament spool backwards before you load the filament. I read somewhere that there is some kind of mechanism which locks the Support Shaft.
Don’t know why this happens but after you turn it backwards and then load the filament, i never had problems again
I have noticed this as well… the Active Support Shaft does sort of lock when in idle mode. It can be broken free quite easily when rolling in reverse. I will give this a try. Thank you.
The Active Support Shaft/Roller is indeed seizing up during feeding operation. I have tested this theory to validate. The test is quite simple, just pull the spool out of the AMS and put your fingers in the spool center so it can rotate as the First Stage Feeder pulls in the filament… you will notice the Active Support Shaft/Roller is static until it reverses and “unloads” the spool. This info is also documented in Bambu’s Wiki. But I had to verify and validate this for myself. You can also visually see the gear arm retract away from the Active Support Shaft/Roller in the First Stage Feeder while loading and engage during retraction/unloading phase.
You are correct with the correlation between full/empty spool angular speeds and the linear length of filament dispensed. However, the Active Support Shaft/Roller is not driving during the loading phase–it is driven.
Operation of the Active Support Shaft/Roller:
Loading – Driven (static; no motion; passive)
Unloading – Driving (actively spinning)
I appreciate your feedback. I am open to all feedback as I am simply looking for the root cause.
I use about 300g of extra weight. However this is probably more than is really needed. There are lots of “spool weights” on Makerworld that use 5-6 AA batteries which is about 150-200g of weight.
Hi, I’m having the same problem with slot 4 on an AMS 2 Pro:
while I am loading the filament, the feeder pulls it in but the Active Support Shaft remains stuck, causing various problems such as the spool hitting the top cover, the filament being scraped by the ring nut, and strain on the various feeder gears that continue to pull.
I was wondering the same thing.
It’s currently printing, so I can’t run any tests, but has anyone else solved this problem?
In any case, it is strange that this problem occurs with both full and empty reels.
Has anyone been able to investigate the issue further to determine the cause of the problem?
I managed to test it, and this only partially solves the problem because when you load the filament, it moves back and forth several times.
When I insert the spool, I rotate it backwards and then insert the filament.
At that point, the spool is able to turn, and the Active Support Shaft does not get stuck.
However, when it brings the filament back and then takes it back, the same problem occurs again.
So yes, this may be a workaround, but it is not the solution.
I’m afraid this will also happen during printing.
Before sending it, I checked that everything was clean, and in the end I found this situation:
I am testing two possible solutions. Results have been positive so far, see my other thread.
Weight generally helps, if it is always broken then the gear in the feeder by have striped the shaft splines. Someone has repaired striped splines with super glue.
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