PETG-CF crack/scar on P2S, bad overhangs and bridges

Bambu Filament and Accesories Filament
1

Hi everyone,

I’m quite new to 3D printing, so I’m not fully sure what information is useful here. If you need any specific screenshots, settings, slicer previews, photos… I can upload them and update the post.

I’m having a recurring issue with Bambu PETG-CF on my Bambu Lab P2S.

A visible crack/scar appears on the side of the print during a few specific layers. It looks like the filament does not stick properly in that area, then some material gets dragged by the nozzle and leaves a bad horizontal mark on the part.

The strange thing is that the rest of the part prints mostly fine, and the defect seems to happen only around certain layers. From what I can tell, it may coincide with the point where a small overhang starts, but I’m not experienced enough to know if that is actually the cause.

Basic setup:

  • Printer: Bambu Lab P2S
  • Nozzle: 0.4 mm hardened steel
  • Filament: Bambu PETG-CF
  • Filament profile: default Bambu PETG-CF profile
  • Layer height: 0.08 mm
  • Filament dried: more than 18 hours at 65°C
  • Manufacturer nozzle temperature range: 240-270°C

I know 0.08 mm layer height may not be ideal for every situation, but I don’t think that alone is the issue because most of the part prints correctly. The problem appears in a very specific area/layer range.

I’m also having generally poor results with this PETG-CF in other situations:

  • Overhangs look very bad.
  • Bridges look very bad.
  • The solid top layers printed over gyroid infill sometimes fail or look messy.
  • Even the purge tower looks bad sometimes, because the internal “ribs” seem to behave like small bridges and the material does not connect well between them.
  • The nozzle sometimes seems to collect or drag small bits of filament.

I have tried rotating the part on the build plate, but the issue seems related to the model/layer area rather than just one physical side of the printer.

I’m currently planning to run calibrations from Bambu Studio, including temperature, flow rate, pressure advance / flow dynamics, max volumetric flow, and possibly retraction. I’m not sure which one is most likely to help with this specific problem.

My current guesses are:

  • overhang wall settings
  • cooling
  • flow rate
  • pressure advance / flow dynamics
  • seam/restart behavior
  • max volumetric speed
  • slicer pathing around that layer
  • nozzle dragging material that failed to stick properly

I’ll attach photos of the defect and some of the different tests I’ve done.

Has anyone seen something similar with Bambu PETG-CF? What settings or slicer preview information should I check first?

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It seems to happen around this specific layer range, only on the left side of the part, even though the model itself is symmetric.

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1 Like
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In 99,9% filament is not dry enough, especially if you use PETG. PETG sucks anyway. Best way to handle PETG is not using PETG but a different material :joy:

Sorry that won‘t help you I guess but it‘s the best tip I can give. Avoid PETG wherever you can.

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I chuckled reading that, because I looooove PETG, it’s most of what I print. It’s sticky and sometimes faintly stringy but so long as it starts out dry it’s reliable for me.

OP, have you tested out some other temperatures? Some of those photos look similar to issues I had with some PETG that turned out to print better 10° cooler than normal.

Also you will save yourself some sanity if you chop out most of the model and make test prints of only the problem areas.

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Yes many people love to print PETG. That’s alright with me but my personal experience is different. I do print well nearly all other materials from PLA, ABS, ASA, PA-6 and 12, PP, TPU, vario TPU, any filaments with carbon and or glassfibre and much more. I print any filament with love but PETG. No other material has caused me bloo of deaths and destroyed print heads.

Maybe this depends on me but I have no luck with it. Good to hear on the other hand that you like printing it so much.

Especially carbon fiber reinforced PETG has big problems in layer adhesions no matter what brand you choose. It seems that your problem is not your fault, it probably relies on the filament. The PS2 is such a good printer that I don’t think it comes from that.

1 Like