AMS Slot 3 not unloading

Bambu Lab AMS
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Yep, another victim of the slot 3 doesn’t unload. I feel like this is a pretty big issue to be honest.

I have 3 Bambu printers, 2x X1C, and 1x P1s. I have bought all 3 within the last 3 months. These printers are fantastic, they print so well. I’ve even convinced a couple of people to buy their own, to be honest, it isn’t difficult to do, lol. But slot 3 on the AMS is unusable for anything but single color prints that you don’t care about. Since almost every print I do has a least a little multicolor it makes using slot 3 extremely difficult. And I really mean slot 3 here. Not only on 1 printer mind you, but every single AMS that came with one of my printers has the issue with slot 3. That’s right! I just received my 3rd printer yesterday, got it running and went to print. Slot 3 fails to retract.

Just to note, my AMS with my first X1C is working right now in slot 3. Bambu sent me a new internal hub and motor, this resolved the issue. But that took a couple of weeks of going through multiple fixes with their support. And just to add, none of the slots work with PLA-CF. Which is comical really. They send you a sample spool of PLA-CF with an X1C and AMS purchase. But I digress.

So what have I tried to fix the issue. I have printed and tested multiple things to get the angle correct inside the AMS. I have printed parts to help keep the tube straight entering and exiting the external AMS hub. I have printed the piece that sits on top of the tool head to make the filament straighter when exiting the tool head. I have smoothed out all the ptfe tubing to make sure there are no sharp bends, but the biggest bend is always inside the printer. Not much I can do about that. I think if they edited their code to put the tool head in the front left corner while extracting the filament it would help. This would straighten the ptfe tube in the printer and relieve some of the friction. Also using a motor with a bit more torque in the hub would help. They used brushed motors instead of bldc motors in the hub. Guess they didn’t want to splurge on the controller for bldc motors.

Anyway, I have 4 open cases with Bambu support right now, but their support is awful. I’m going to have to tear apart the AMS unit and do this, video that, more pictures of this, print that, try this. No, go back and do that again, all the while waiting at least 1 day in-between replies.

I put a reference back to my first ticket for the 2 AMS issues, but they will probably want me to go back through it all again. But if all the AMS units show the same issue, well you know the saying. If it walks like a duck…

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I have the impression that everything has to wear in as well. I have to admit that I have now replaced the buffer with the AMS HUB. All the printing options that are offered have not helped me. Without having made any further adjustments, I no longer have any problem with slot 3 or the other slots.

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Actually, my first X1C now has an AMS hub on it too, with another AMS that I bought. Interesting enough, haven’t had issues with slot 3 on that one. Well, except for PLA-CF, which doesn’t retract in any slot on any of my printers.

I’m going to try running PLA-CF through slot 3 of my new printer and see if that helps. This was a suggestion on a video in a similar thread.

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Odd… Only because this week my slot 3 suddenly refused to unload after a year of continuous printing on my X1C. I pulled everything out of the AMS, yet it still showed slot 3 as loaded into the print head. I removed all the PTFE tubing to no avail. No broken or stuck filament at the print head or buffer. I tried loading different filament in slot 3, but it wouldn’t load at all. It would just endlessly spin the spool in reverse trying to unload this seemingly nonexistent filament from the head. I started to worry if I was dealing with something more problematic. Finally I decided to open up the AMS to check all of the internal PTFE tubing. There ended up being about a half inch of broken filament jammed right at the last filament sensor in the back of the AMS. I couldn’t load filament from any of the other slots because the printer would endlessly try to unload slot 3 before doing or allowing anything else. Once I removed the piece, I was totally back in business. Back to normal! It was only tied to slot 3 because that was the last slot it had used before the failure took place. Wacky!

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So, I ran some PLA-CF through slot 3 for a short print, printed a bed scraper. Then ran regular PLA through it and had no issues, 2 prints in a row. I am now doing a 13 hour print to print a bunch of silica containers. We’ll see if it unloads after that.

I’m also going to try this through one of my other AMS units that has the issues.

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Just as an update, I didn’t run the PLA-CF through the other printer since it is my P1S and doesn’t have the hardened nozzle or extruder gear. Almost hit print though, lol.

Bambu sent me their canned response to retraction issues. Why do they make adding pictures and videos and logs necessary to create a ticket if nobody even looks at them?

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