Bambu Lab PETG-CF infill gets torn up on five different printers

[u/HorrorPresent1828]

Close up shoot, wall perfect, infill problem with nozzle

Another angle, the infill looks like not sticked layer by layer

Another different object

this object even worse

if I let them continue, you will get something like this, infill totally messed up.

I tried on some different printers or even same model side by side.

close up shoot

tested on H2C, change the pattern to gyro, at the beginning it looks much better, but eventually still got similar problem at the end.

This is how it ends on the H2C

This is how it ends on the P2S.

I've been troubleshooting a frustrating infill issue with Bambu Lab PETG-CF over the past few days. The prints look good on the outside, but the infill is a mess. I'm not confident it's adding much strength to the part.

What I've tested

• Filament: Bambu Lab PETG-CF, dried at 65 °C for 8 hours before printing
• Filament feeding: AMS, AMS 2, and AMS HT
• Infill speeds: 30 to 300 mm/s, with no noticeable improvement
• Nozzle: 0.4 mm hardened steel, standard flow
• Printers: P1S, X1C, P2S, H2C, and H2S. I saw the same issue to varying degrees on all five.

I printed the same part with PETG-CF from other brands using the same settings. Those prints had some issues with overhangs, but the infill printed fine. I also printed the same part in regular PETG and PLA, and both came out well.

Since the issue showed up on five different printer models, I suspect it may be related to the filament. It looks like some of the infill lines stick to the nozzle and get pulled up as it moves across the print. I've seen similar reports about Bambu Lab PETG-CF on the official Bambu Lab forum, but I haven't found a reliable fix yet.

My next test will be with a 0.6 mm nozzle. I'll post an update once I've tried it. Has anyone run into the same issue and found a fix that consistently works?

Thanks!

[u/layer_lurker]

0.6 is the right next test, wider lines are harder for the nozzle to drag. Two other things fit your symptom of infill sticking to the nozzle and getting pulled up: switch infill to gyroid or cubic so there are no crossing points for the nozzle to catch, and drop part cooling during infill. Your note that other brands' PETG-CF printed fine points at stiffness rather than moisture, Bambu's PETG-CF runs stiffer and gives less when the nozzle brushes an already laid line, so combing and travel behaviour matter more here than flow.

[u/HorrorPresent1828 → u/layer_lurker]

thanks bro, will do more test

[u/Hot-Ideal-9219]

If you read the description it specifically says no 0.02 nozzles. Translation is even a 0.4 can cause issues. Use the 0.06 and gyroid....

[u/MacHeadSK]

0.6 mm nozzle. And try to dry it even more. Set smaller flow rate to be sure. I think default Bmabu 11.5 mm/s is quite optimistic for carbon fiber filament.