Bambu Lab PC filament not extruding mid print

Bambu Filament and Accesories Filament
1

I need to make a piece with high temperature resistance on X1C.
Got a Bambu Lab PC filament.
2nd time now, about 30% in the print, the filament seems to stop extruding and the print head just moves in the air. Reminds me of a dog simulating something, but he is all alone.
I am using the BL defaults for this filament.
The chamber is heated to 60 Celsius stable before starting and during print.
Everything I read about this issue is about hotends getting clogged, but after I stop the failed print, I can load and unload the filament just fine and it extrudes just fine also.

image

Any clue as to why this is happening and maybe a fix?

2

May this PC issue be related to heat creep?

That could be mitigated by checking (and reducing) the number of retractions and trying lower chamber and build plate temps.

But I remember that @Olias has far more experience with PC than I do and may be able to give much better advice and guidance.

1 Like
3

I don’t have any experience with Bambu PC, I use other brands but my extrusion temps range between 245 and 280 depending on project. So I don’t see anything wrong with your settings.

The one question that I have though is this: Are you operating this through an AMS and if so, have you tried to feed the spool independently? I ask because your symptoms could be explained as filament feed being snagged. Also, checking the PTFE tubes for wear can also be a remedy. If nothing else works, try forcing direct feed of filament using the control panel to ensure that your nozzle is clog free. Finally, make sure your parts fan is off, this will eliminate premature cooling in the Hotend as a possible culprit.

2 Likes
4

I am using the AMS. I even switched slots to rule it out, to no avail.
PTFE tubes are in good condition.
The nozzle is clog free because when I unload/load/unload I can see filament dropping in the chute. Will try to manually feed it next time.
Also, the first 20-23% of the model is printed just fine, so the issue starts somewhere during the print.
Until now, 3 prints failed exactly like this.
Will try to print the same model with ABS to rule out a problem with the model itself. No clue if this is possible, but being a total greenhorn, I need to learn somehow.
If it prints in ABS, will try to turn off the part cooling next.

Thank you for the tips.

1 Like
5

This helps in ruling out the AMS slot, but still leaves the lengthy PTFE path as a contributor. You can significantly reduce the potential friction by printing from the rear spool holder.

This is what led me to speculate about heat creep. I can not get my X1 all the way up to a 60°C chamber temp but have experienced similar issues when first experimenting with PC.

And this is why I am unsure about heat creep. In the cases where I did have heat creep, that led to a clog. But again, I am rarely printing PC so that may be a particular curiosity. Of course, during unloading, the nozzle would have had a chance to cool and the PC to shrink a little bit.

Always a good approach to rule individual factors out. But it is unlikely that a particular geometry leads to this kind of extrusion error. Do you have a picture of the failed print? In particular the failure?
And just on the off chance: Do you use ironing on the model?

:+1:

1 Like
6

It sounds like you’ve exhausted most of the common troubleshooting steps. If you like and would care to do so, upload the 3MF file here and note where the defect occurs. Does it occur at the same location? I would be happy to see if I can view some sort of artifact in the model in my slicer.

Also, while I think about it. Does this happen at the exact same layer and spot? I ask because that then calls into question as to whether this is a file corruption issue. If that is the case, sometime the Micro SD card get corrupted. A reformat of the card generally clears it up but if that turns out to be the issue, you’ll want to replace the card with a high endurance micro sd card. The ones that ship with the printer are poor quality and the nature of the Bambu architecture tends to chew up regular SD cards which is why I generally use the high endurance cards.

2 Likes
7

You were right the 1st time @Olias !
The part cooling fan was the main culprit.
I have modified the filament like this:

image
image735Ă—501 21.6 KB

image
image736Ă—396 21 KB

Worth mentioning that I have tried increasing the nozzle temperature without disabling the part cooling fan before without success.

The print is pristine now, but…at 81% I got a false spaghetti detection error and because this is the 1st time I am seeing the error, I just stopped the print from the machine, without realising I could have continued.
Weird thing is this X1C is in LAN mode, timelapse is disabled, it is not recording and it’s internet is blocked. I was under the impression that this spaghetti detection was a remote/cloud thing. On the other hand, I had Bambu Studio left open with the video stream playing. Maybe the detection is done through Studio? No clue.
I have now disabled the detection of italian food and hopefully will finish this one 128g piece before I run out of this PC filament.

I read about the SD card problem before opening this topic and I’ve formatted it, to no avail. This is what I am using:
image

Thank you for the advice.
Thank you @EnoTheThracian & @Olias

1 Like
8

Quick update.
Had to print some more parts in PC and discovered that turning off the fan only worked for my 1st model.
Wasted some more time “tunning” (blindly tweaking stuff) only to discover that besides turning the fan off, I also have to lower the nozzle temperature down to 260 Celsius.
So, in my case, with Bambu Lab PC filament and X1C printer, with the chamber at 60 Celsius I need to have these settings to print without issues like heat creep:

image
image730Ă—935 42.7 KB

image
image728Ă—613 29.6 KB

Hope it helps someone.

2 Likes
9

Small but significant correction to everything I’ve written so far in this topic.

I’ve had this printer since around mid-December 2024—so close to two months of use.
Translation: I’m a total noob and have no clue.

TL;DR: The freaking extruder fan was busted. The small 25.5 mm one that’s supposed to cool the nozzle.

Ever since I bought this printer, I noticed a high-pitched sound coming from it.
Since it was a brand-new device, I assumed that was just the normal sound it made. Plus, I keep it in another room, so I could barely hear it.
Imagine a sawmill next to your house—that was the sound.

After dealing with so many clogs and wanting to get to the bottom of it, I removed the extruder with the fan, replaced the thermal paste (which was nothing like a paste—more like dust), and put it back in.

That’s when I discovered the source of the high-pitched noise. I noticed the fan was barely moving.
I dismantled everything again, but this time, I kept all three cables plugged in while holding the fan in my hand.
The poor thing was barely spinning, screaming like a devil, and moving almost no air.

I removed the back seal and tried adding some specialized oil—no change.
The only thing that fixed it? I gently pushed the blades outward until I heard a click. The noise stopped, and the fan started pushing air. Not a ton, but the difference was night and day.
Pushed the blades slightly toward the motor, the noise came back and the fan slowed down a lot.

Conclusion: I received a faulty extruder assembly, which cost me a lot of filament, time, and gray hairs.
A big thank you to the person who assembled my unit.
Also, this model of fan is a joke. If anyone knows a better model, please share.

So, if you were bored enough to read this far—check your extruder fan if you’re dealing with frequent, random filament clogs.