Extruder gear stuttering/skipping

Bambu Lab P1 Series Troubleshooting
21

It was really interesting to read through all this,

im having the exact same issue as you @buckeyestargazer and my problem solving went pretty much along of what you did.

For context,

My P1P has about 3000 hours of Print Time and i never had any issues before that, regulare maintenance every few hundred hours etc.

About 4 Weeks ago one of my Prints through the night failed, underextrusion and clicking noises
I noticed the yellow extruder Gear was skipping

Checked for a clog → nothing
Changed Hotend → changed nothing
Cleaned out extruder → changed nothing
Changed extruder → changed nothing
Changed stepper motor → changed nothing

Changed Hotend another time → suddenly started printing again

After about 20 hours of printing the same problem appeared again.
The Printer extrudes fine without the hotend attached, no clicking whatsoever
So it has to be something about the backpressure of the Hotend

Changed the ceramic heater of the hotend → changed nothing

I also checked on the nozzle size in the printers settings, was correctly set to 0.4 Nozzle

Then did a firmware reset, because why not at this point ^^ → also changed nothing

Im kinda at a loss here.

The only rational i can come up with at this point is sth about heatcreep

Maybe heatcreep deformed the plastic carrier over the last 3000 hours just enough so the 2 Gears arent in the same place they used to be?

But i dont even know how to check for that, Bambu Lab doesnt seem to sell the plastic carrier for their Printers.

Have any of you figured sth out?

22

Is the contact pressure of the idler set correctly?

1 Like
23

i am having this same issue as Joel97. ive followed the same steps and im at the same point. only 1500 hours of printing and suddenly having extrusion issues. changed hot ends numerous times, cleaned and lube extruder, replaced extruder gears, replaced stepper motor, nothing has changed

1 Like
24

Double check you have the correct sized nozzle selected on the printer. Others have had extruder weird extruder problems and it turned out it was simply this.

3 Likes
25

Good idea, but yeah, i already checked that, when i lower the idler pressure just by a bit, the filament wont be gripped/extruded anymore.

26

Then I would completely replace the PTFE pipes

27

Was this EVER resolved?
i have the exact same issue on one of my X1C’s, 1900h on it
changed all ptfe tubes
extruder motor
hotends,
extruder gear assembly
usbC cable
TH board is next, but im waiting for the new lidar module…

28

I have the same issue. Skipping gears, no flow, unable to print anything large without loud skipping and clicking noises.

29

Having same issue. Happened in the last 30 mins of my first CF print so assumed it was a clog.
Did a flow rate check PLA, extruded fine, then ASA, fine. Then ran a proper print in ASA and extrusion issue again.

Now it’s not extruding and yes, nozzle type is correct.

30

I find myself in the same boat with one of my P1S machines. It’s been printing fine for over 1000 hours, but now (suddenly) the extruder gears are skipping.

Like others in this thread, I replaced the hotend with a brand new hotend assembly (new thermistor, fan, hotend, etc). Did not solve the problem.

Next step is to try replacing the extruder unit, but I have low hope that will solve the issue given the discussion here. I also opened a support ticket with Bambu on the long shot they’ll have additional context by now.

31

I have the same problem with my X1C. After many tests I found out that either the motor, the motor driver or the power supply have a problem. The motor does not have enough power to move the filament. Normally the motor just spins when I have heat creeping.
So I supported the motor with my hand while spinning and suddenly it extrudes again.
This means the motor can’t apply enough force. If the motor was defective, it wouldn’t actually turn at all. Since there is only the possibility that a winding in the motor is defective.
I therefore think that either the motor driver or the power supply is causing the problem.

32

Upon additional testing today, I was able to narrow the problem to the extruder unit. After replacing with a brand-new extruder unit, the printer was able to feed filament through the hotend without skipping.

Afterwards, I disassembled the removed extruder and found that the passive gear assembly (the one in the gray arm…not the big yellow gear) is not spinning freely. It takes significant force to make the gear move, which I don’t think is normal. I hit the gear with compressed air and manually turned the gear 360 degrees, but I do not see any obvious obstruction or debris. I will try soaking the gear assembly in IPA and see if that frees the movement.

In any event, it seems the added friction in this gear was likely the specific cause of this failure, though it remains unclear how or why exactly it suddenly reached this state.

I’m sure this won’t be the solution for everyone, but it’s good to know that sometimes a skipping extruder can be due to a frozen gear in the extruder assembly.

33

Final update: after soaking the passive gear assembly in IPA, it now spins freely. So, somehow (¯_(ツ)_/¯) “gunk” built up on that gear to the point it could not spin and that cause the extruder motor to skip.

This printer only prints PLA, so not 100% how this gear got “gunky,” but problem solved (for me). Hope it helps someone else.

34

Bambu Lab Support is now sending me a new Motor. Support thinks that the problem is due to a stiff motor. But I don’t think so. I have measured the motor windings. They are ok. The motor is also working. As long as I print PLA with a cold plate, it works. But only with the door open and cold room air.
I noticed that the extruder motor generates a lot of heat. I also find it abnormal that the motor is sometimes energized, i.e. under load, even when no filament is loaded. This of course generates additional heat. I have now asked support if this is normal? I am looking forward to the answer.
For me, this is incomprehensible.
The motor generates so much heat which then heats up the extruder gearbox. If the filament is then loaded and it takes too long to start printing, the PLA or PETG filament has already become so soft due to the heat from the gearbox that the filament is crushed directly behind the extruder gearwheel at the start and does not even reach the hotend.
This cannot be normal.
Has anyone already observed this?

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35

As seen in the picture shared, the section which is compressed is probably caused by Heat Creep. Please read this wiki article for more information: Heat creep and how to avoid extruder/hotend clogs | Bambu Lab Wiki

Based on what you have shared, the motor is overheating and this is the cause of the clog, but considering the printer works as expected with the top/door open, the issue might also be related to the environmental temperature and the filament. If the door is closed, and a higher temperature is used for the heatbed, the chamber temperature is higher. Have you checked the temperature of the enclosure, when the clog occurs?

One of the reason why the motor can overheat is if the extruder is not clean, and the movement is not smooth. It is recommended to try and manually turn the yellow gear of the extruder, while the printer is turned off. If it cannot be turned, it is recommended to clean and lubricate the extruder by following this wiki guide: Extruder Maintenance Guide: Cleaning and Lubrication - P1 series | Bambu Lab Wiki

Of course, after you receive the extruder motor, you can try to replace it and confirm if it overheats again or not, and if it solves the problem.

36

Hello, thanks for trying to help. I know this wiki. I have 2 extruders and 5 hotends here that I have tested. I also have the comparison to earlier when the printer behaved differently. I have been using this filament for a very long time. And suddenly the problem occurred without any changes in the external conditions. The extruder and the hotend are not the problem. Both are working fine.
The lid and the door are always open when printing with PLA. The problem also occurs with PETG.
I can feel that the heat in the extruder radiates from the motor. The cold end of the hotend is much cooler than the extruder. The build chamber temperature is also fine.
When I touch the back of the print head (where the motor is installed) and the gear that sits on the motor, I can barely touch it because everything is so hot. This heat transfers to the extruder gearbox. I can only touch it with pain because it is so hot.
And I feel that the motor is under load even though no filament is loaded. I would like to know why this is? Is it programmed that way or is it due to a defect?
This is unnecessary. No wonder the motor gets hot.
I have noticed that the motor generates heat under load in idle mode since the beginning. But recently it also lost power and I can no longer extrude.
I am curious if the new motor will change anything. But I don’t think so.

1 Like
37

@SupportAssistant Do you not have an answer to my question? I would like to know if it is normal for the motor to be under load when the filament is unloaded.

38

Yes, it is normal.

When loading the filament, the motor is engaged to move the gears of the extruder.

The same applies for the other motors. Once the printer is homed, the motors remain engaged until the printer enters sleep mode (if a print is not started).

At this point, I recommend waiting for the replacement motor, as it will probably solve the problem.

39

@SupportAssistant
But that is exactly the problem. When no filament is loaded and there is no print job, the extruder motor should at least go into standby mode. I don’t know what temperature this motor normally reaches when everything is working correctly, i.e., when there is no defect. However, in my case, the motor always generates a lot of heat when it is on, i.e., under load (braked). So much heat that you cannot touch the extruder and the motor gear. It’s no wonder that the PLA and PETG filament becomes soft and the extruder compresses it.

Can you tell me how warm the motor normally gets when there is no defect?

40

I have this same issue. funny how my prusa is slow tortoise but reliable, the Bambu is the Hare but now just a door stop.