There are many threads on first stage feeder retraction issues, however, while the symptoms are similar in most of them, the only ones i’ve seen with this exact same issue, are unresolved. With that in mind, let me explain.
I got my P1S in August last year. One of the First Stage Feeders was like this on arrival, and the 2nd became like this after literally the first print because of a factory-tangled spool. I guess the strain weakened the motor. (Not counting that one, since it was a filament issue). Yesterday, another one started failing to retract after I put a full spool on it. Its been noticeably noisier than the other slots for a while, so I think its been dying for a while.
So what is the problem exactly?
When the feeder tries to retract, it struggles to spin the spool. Usually it spins really slowly then stops, but the gears continue spinning. I need to manually turn the spool a little bit to get it to switch to the next one.
A couple of observations:
- If I lift up the spool, the rubber rollers start spinning, but when I put the spool back down, it can’t turn it.
- Sometimes during its struggles to retract the filament, it will engage the upper gear(the one that moves the filament itself) and it will retract fine.
Video of the issue:
Correct me if I’m wrong, but it seems like the AMS is designed to retract by only spinning the spool, without actually pushing back the filament. This seems like a flawed design based on my observations above.
Firstly, the filament tension is often too high to rely solely on the rubber rollers.
Secondly, the gear that spins the rollers is on the same axle as the main gear in the centre, but isn’t secured to the axle. This means that when enough weight is placed on the rollers, the main gear and axle spin but the roller gear doesn’t. I’m not sure if this was done intentionally to avoid excessive strain on the motor, in case of tangled filament, etc, but it doesn’t seem to be working as intended.
I’ve ruled out most of the common causes for issues with retraction:
- Debris in the tubes/1st/2nd stage feeders
- Worn gears
- Cardboard spools
- Sharp bends in the PTFE tubing
- Worn rollers
- Lack of contact between rollers and spool
- Spool scraping against the sides/top of the AMS
If anyone has a solution(apart from replacing the feeder) or a similar problem, or a better idea of how exactly the first stage feeders work and why this might be happening, please add it to the thread. I know the feeders are a consumable part, but with less than a thousand hours on this printer, it seems a bit too soon.
My theory as of now is that the gear that spins the rollers is not meant to be that loose, but that seems a bit too simple.