P2S - Extruder Gear Slipping

Bambu Lab P Series Bambu Lab P2S
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I am trying to trouble shoot an issue with no suggess on my P2S with the AMS Pro 2. I am only prining with Bambu PLA. All of the sudden it isn’t printing correctly. I can load, unload, and extruder filament using the menu, with no problem. I can also heat the extruder, via the menu section, and manually push filament through the extruder. I have taken the extruder apart and cleaned it. There never was a clog, and the gears look fine to me, even under close inspection. When I try to do a test print, it goes through all the typical procedures. Once it starts the Benchy test print, the print starts way over to the right side of the build plate, which I’ve never seen happen before. It seems to start printing fine, but have a few layers I get a clicking sound from the extruder. To me, it seems like the gear is slipping. It moves slowly, extruding filament, then all of the sudden the gear RPM goes way up, and seems erratic. I have to idea what the issue is, but I suspect it must be the extruder motor. I have never tried to tighten or loosing the tension screw on the extruder, and don’t know what it would all of the sudden change. I should mention that this happens regardless of which filament spool I use. Now that I have the extruder tension mechnism removed, I have no clue how to put it back together, and expically how to set the tension correctly. I have file a technical ticket with Bambu, but we seem to be going back and forth instead of addressing what the issue is. It seems like it just an automated responds system. Obvisouly I would like to get my P2S up and running again, since this happened 2 weeks ago.

I should mention that I’ve been 3D printing since 2012. My first 3D printer was via Kickstarter campaign. The printer was called Robo 3D R1. Since that time I have owned several other 3D printers, several Ender, Creality, a couple of Prusa and two Bambu Labs. Even so, I’ve been one of the lucky ones and have rarely had any 3D printer isues, so I am not well versed in trouble shooting.

PS: I should also add; I disconnected the AMS, but I only unplugged it. I did not reroute any of the existing PTFE tube I unloaded the filament that the AMS had loaded. Then I shut off the P2S. I mounted a Bambu PLA spool on the external holder, and fed the PLA by hand until it reached the extruder. I energized the P2S, and loaded the external spool. I then tried a test print, and the same clicking/slipping issue is happening. It will start the print but as you can clearly see it is not printing correctly. Eventually the print errors out. I have attached a video of the slipping that occurred. You can visually see the gear slipping from the increased RPM

You’ll see what I am talking about around the 10 second mark in this video;

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1 Like
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This is most likely a partial or full nozzle clog. You should have gotten a small needle with your printer. Heat the nozzle to 250 degrees, and then move the needle up and down through the nozzle, then try again

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Can you explain why I would have a clog in the hot end, when I can unload, load filament, and then extrude filament when pressing the extrude button, even if I press the extrude button many times? I have also removed the PTFE tube, headed the nozzle to 240, and manually pushed several inches of PLA filament into the extruder.

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Also, what is the procedure for replacing the tension mechnism and protocol to tighten the tension screw?

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I can’t really explain why or how. I just know that my p1s did the exacct same thing a few months ago, and it was just a clog in the end.

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i am not sure about replacing, as I have not done that, but as for the screw, you just have to tighten it all the way.

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I have figured out how to assemble and tighten the tension block, so that is no longer an issue. As I said before, I do not have a clog.

1. I have completely disassembled and cleaned the extruder. There was nothing clogged or filament fragments.

2. I heated the extruder to 240 degrees and manually extruded filament using the up/down buttons in the menu system. The filament extrudes fine from the nozzle.

3. I also heated the extruder to 240 degrees and used the needle that comes in the tool kit, and inserted it into the extruder and down through the hot end.

As I’ve said, it is not extruding the filament properly. It feeds smoothly for a while, then starts slipping. It will start a print, but then errors out, due to the erratic and inconsistent filament extrusion. Tech support hasn’t been helpful so far. They are simply tell me to do things that I have already done, and explained, just like I am here.

-JW:

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That sounds less like the gear randomly slipping and more like the extruder is skipping because it is meeting too much resistance somewhere. In other words, the filament may not be fully blocked, but something is making it harder to push through during an actual print.

I would be careful messing with that unless Bambu support specifically tells you to. I have not really seen people needing to adjust extruder tension on Bambu machines under normal use, and changing it can add another variable while troubleshooting.

Since you already have a ticket open, I would lean on support for that part. In my experience, they are usually good about walking through the issue and sending replacement parts when something is actually defective.

That can still happen with a partial clog, nozzle restriction, or the nozzle/hotend not being seated fully. Loading/extruding from the menu is slow and controlled. A print demands more consistent flow, more retractions, and more pressure, so a partial restriction or slightly loose/improperly seated nozzle may only show up once the print starts. This is also a very common sign of a defective nozzle. Just to be sure can you just go over everything a get a bunch of good photos.

Where I would start:

I would confirm the nozzle/hotend is installed properly and locked in securely. You would be surprised how often that ends up being the issue.

After that, I would run the built-in nozzle cleaning/cold pull routine from the printer screen (use PLA to clear the ABS option). I would run it twice to make sure there is not a partial restriction left in the nozzle.

Alternatively, if you have another nozzle/hotend available, I would swap it in next. That would be one of the fastest ways to rule out a defective nozzle.

Since the extruder/tension mechanism has already been taken apart, I would also re-run the full printer calibration with everything back together.

Then I would send a fresh Benchy from Bambu Studio on your computer, not from the app and not from the printer’s built-in file. Make sure it is sliced with the correct P2S printer profile and the correct Bambu PLA filament profile and its placed in center or wherever you want. (if this still prints elsewhere lmk)

If it still clicks or starts under-extruding, pause it after the first layer or early into the second layer and post clear photos of the first layer, the installed nozzle/hotend, the extruder gears, the tension mechanism, the PTFE connection, and the filament path.

Hopefully this is not repetitive, but I am just trying to rule out the simple stuff first.

1 Like
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Thanks for trying to help. I will tear everything down once again and start over. I will also order another hotend.

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at this point, I would inspect the yellow extruder gear to see if it has any messed up looking teeth where it could be catching. otherwise, you could have a bad extruder motor.

-BoneForgePrints

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To clarify, other than maybe removing the toolhead cover and then nozzle, there shouldn’t be allot of (if any at all) teardown for this. It’s best to leave that to bambu support so that we minimize adding any new variables.

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Looks like you didn’t view one of my photos. I took a tooth brush to all of the gears. They are all clean, and no damage to any of the teeth. The bearing truns smoothly. I can here is spin when I used compressed air on it.

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There isn’t much I can do about that, since I have disassembled everything in the extruder. Tech support is aware of that.

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See the issues I had with the 0.2mm nozzle in the other thread. I would also check:

  1. Filament roll is not tangled, sitting properly
  2. Try a different slot in AMS
  3. Check/clean AMS
  4. Check/clean/lubricate filament buffer
  5. Try a different nozzle
  6. Add a washer to the screw that tightens the filament (on stop of extruder head) - there are other posts on this.
1 Like
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oh my bad. I’m sorry about that. In that case, maybe you have a bad extruder motor. I know you said it isn’t a clog, but when I had this issue, I didn’t think it was a clog either, but it was in the end.

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I’m still not getting anywhere with technical support. I’m sure I’m dealing with AI answers. I just noticed something that could be the issue. It’s sort of odd too. At the moment, my P2S is idle, but plugged in. If I go to the spool in slot one, I can’t easily rotate it by hand. If I go to the other three, they all move freely. I haven’t a clue why it’s stuck. I’ve also seen this happen on two of the other spool slots, when the machine is idle. I have no idea why or how the rollers may be ‘stuck’ and preventing the spool from rotating.

I am totally lost to what the problems might be, nor how to solve them. It’s pretty obvious if the rollers are the issue, therefore keeping the gears from pulling from the spool, it would make the gears slip. Has anyone ran into this issue before?

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if i may ask, have you also appiled lubricant grease to both gears in the P2S extruder?

and with the ams i can only think of the gears in there having debree on them, or that maybe the bearings are broken, or something is blocking the roll from spinning

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Well, without any additional follow up info on the steps I listed above, there really isn’t much new info to go off of here.

As for your AMS issue, it can sometimes bite and hold onto certain spools. Often, spinning the spool forward before pulling it back helps unlock the rollers. That said, this isn’t your issue since you already said you tried using the external spool mount and the problem still happened.

We need more info and photos to help with this.

As for support, I have had a lot of tickets with Bambu, and I have never known them to hit a dead end and just leave it there. If you work with them, answer their questions, and go through the checks, they warranty parts, and even full printers, when they cannot solve the issue.

Overall, it seems like we are missing quite a few pieces of the puzzle here. More info and photos are needed, and screenshots from support may at least help show what has already been checked and ruled out.

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Are you supposed to apply lube/grease to the extruder gears? Cant find a definitive answer. I do believe they come from the factory greased.

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P2S Regular Cleaning and Maintenance Recommendations | Bambu Lab Wiki

under the section Extruder Cleaning part it shows where to apply the grease (NOT NORMAL LUBRICATION OIL)