Bambu PETG-CF sticking to nozzle, unable to print

Bambu Lab X1 Series Troubleshooting
1

Hi everyone!
First of all I’d like to clarify that I’ve read the big discussions/long threads regarding PETG, so I am aware that the PETG topic should be already hammered into the ground. It is still appreciated if you link a thread/comment somewhere that mentions this issue.

My issue is that on any print with Bambu PETG-CF, the extruded filament is sticking to the nozzle, a blob keeps forming until it is as wide as the silicone cover. Around that time it decides to just stick with a layer, which results in the printhead bumping into it the next layer. Does not happen with different polymers.

Here is what I’ve tried:

  • switching nozzles: 0.4mm and 0.6mm
  • switching layer heights: 0.2mm nozzle, 0.24mm and 0.3mm with 0.6mm nozzle
  • the nozzles are not clogged, damaged and very clean when starting the print
  • coating the nozzle with PTFE lubricant
  • wall order: outer walls first
  • wall speeds: 60mm/s outer, 80mm/s inner, 100mm/s infill
  • infill type: gyroid
  • infill overlap: -2%
  • chamber fan set to 100%
  • part cooling fan set to 10-30%
  • everything else stock Bambu PETG-CF profile
  • everything else my print profile based on these Bambu print profiles:
    0.3mm Strength (0.6mm nozzle)
    0.24mm Strength (0.6mm nozzle)
    0.2mm Strength (0.2mm nozzle)

As for temperatures: With the chamber fan on 100% I get chamber temperatures around 40°C, even with an open door it stays at 38-39°C. Opening the top cover isn’t really an option for me, as one of my AMS is sitting on top of the printe.
Overhangs do not matter for this model, as my only overhangs are from text insets on the model, they print fine without reduced speeds.
I couldn’t really tune anything on the Bambu PETG-CF, k-value and pressure advance look fine and I’m nowhere near max flow with these speeds for the print. Also the prints do come out really nice IF I babysit the printer and stop the print to remove the blob. I have to do this every 30-40 minutes!

The last thing I’ve seen is some artifacts on my print on edges, however not at the location of the seam, here are some pictures of it:

The blob forming:

IMG_0823
IMG_08231920×2560 199 KB

That spot on the left is where the blob stuck to the model, I removed it already:

blob detaching from the nozzle
blob detaching from the nozzle1920×2560 629 KB

This picture shows the artifacts I get, keep in mind this is the opposite side of the seam.

other artefacts
other artefacts1920×2560 304 KB

Could this be the blob collecting filament on the corner? Or a cooling issue? I was thinking this couldn’t be PA/flow issue, as it only appears on some layers. Than again, I printed 2 of these models layer by layer at the same time, they look identical, have these issues on the same spots:

IMG_0819
IMG_08191920×2560 379 KB

ANY help, recommendation, idea, suggestion is appreciated, I’ve been struggling with this enough now!

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2

Have you tried drying it? Not that it looks like wet filament to me at all…

Perhaps try lower extrusion multiplier or a higher K-Value to avoid the buildup?

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3

I’ve had great success with Hatchbox PETG. I’ve been printing on 4 different printers, the Bambu is by far the best.My conclusion, there is a lot of magic involved. Print plate, filament type, filament vendor, and model errors. The last is somewhat rare but totally possible.

PETG is notoriously hard to print, tweaking is almost always necessary.,

I have been using Hatchbox PETG for everything, but now I have a new favorite, courtesy of a friend that does a massive amount of printing - ASA, It’s a more friendly ABS plastic. Super-strong, UV resistant, and I’m getting phenomenal prints with razor-sharp edges

But to the topic, my opinion is you have crappy filament. I get perfect prints using Hatchbox PETG using the ‘generic PETG’ setting on several plates. You do need to use glue stic, though for some of them. My usual is the Bambu textured one, you do have to clean it with alcohol almost every print,

4

Hello and thanks for the reply!
Although the filament was put straight into the AMS from the package it arrived in, when I noticed this issue I thought the same.
So I dried it for 12 hours, although my dryer only goes up to 70°C.
While it was drying I changed the desiccant in the AMS and put some extra in when I put the spool back after drying.

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5

How’s the silicone boot? Is it ripped or missing a section?

Also… not sure I’d stick PTFE lube on the nozzle, that seems as though it would encourage the filament to not stick to the layer below and from then its just going to wrap around the nozzle.

2 Likes
6

It’s a longshot, but perhaps the filament is magnetically attracted to your nozzle. The community has been finding various CF filaments are exhibiting magnetic properties.

Discussion

Side note: Lots of digressing in that thread, no conclusive findings as of yet.

You may try degaussing your nozzle or the filament (somehow, yes that sounds weird.) If this is the issue, no evidence supports any of these claims though.

7

@just4memike @Kallvin
Thank you guys for the suggestions!
The silicone cover looks fine, I clean both silicone cover and the nozzle after each print with a wire brush.

I was thinking about how PTFE could just make things worse as well, however, no sign of layer adhesion problems when comparing PTFE coated nozzle with the nozzle without coating. Nevertheless, this has not helped sadly.

I did order the plastic repellent paint from Slice, will report back when it arrives and I’ve tested it.
As for PETG-CF being ferrous, I’ve seen threads discussing many CF filled filaments seemingly having this weird property.

As for degaussing I’ll keep this in mind if nothing helps, although I’m not sure how I’d do this.

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8

There is already a thread about this problem: Nozzle collects filament when printing with PETG-CF - #15 by hant.szabi

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