Hello,
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.
Any help or insight would be much appreciated.
All of them or just that single slot? They are removable, if you swap it does the problem move?
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.
Does it only do it with that empty spool?
I have tried a few different spools, all are Bambu spools as shown in GIF.
There are three spools in my GIF image.
- The white filament does not have this issue.
- However, the orange and green bambu filaments have this issue.
- The green more so than orange.
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 hope that helps a bit
I add weight all of my spools.
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.
What is the target weight (g) you shoot for per spool?
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.