What's the deal with PETG?

Bambu Filament and Accesories Filament
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Hello All, I’m hoping to gain a better understanding of how to actually make successful PETG prints happen.

Until now, PETG prints have been the bane of my existence with the primary issue being first layer adhesion. I can’t for the life of me get PETG to consistently adhere properly. I’ve tried different plates, higher temps, cleaning the plate, up to 24 hours of drying and I still have not found a silver bullet to the problem that is printing in PETG.

Are there any recommendations that can get PETG to be less of a miserable filament to use? I primarily use BL PETG-HF (which I’ve found is even worse with these issues) but also have similar issues with Inland PETG.

Absolutely any help would be appreciated.

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Here’s an example of how my PETG prints tend to come out.

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Printer model?
Temperatures, hot end and bed?
brand of PetG?
Type of covering?
Try these settings - My P2S P1s and x1c all print petg pretty good at 200 degrees and 55 degrees for the bed. I use the textured PEI plate.

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PETG has so many formulations. Basically any vendors pla can be acceptable at 210/60/full cooling, but it’s just not true with petg.

Yours looks too hot to me, if it’s dry. Given it’s the first few layers fan isn’t involved yet, so nozzle temp down imo as a start.

Everyone in the world is about to tell you to dry it and I too am one of those people in the world, petg loves dry.

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The example above is on my X1C. I’m usually using the defaults provided by Bambu for Bambu HF so…
Nozzle: 230 on first layer, 240 after
Bed: 70
Cooling: off for layers 1-3
Drying: 15 hours at 55

Based on your recommendations, it seems Bambu Lab’s defaults are way too high?

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Possibly, but I live on the west coast, the humidity (normally) isn’t that high, usually about 50% INSIDE the house where the printers all reside. The temp does seem a little high, but who knows?

You didn’t say what plate you are using, using the PEI plate on all my printers has corrected all of my project-not-sticking issues, the only thing I do is wash the plate with dish soap, I haven’t used any glue or stickum in months.

Are you using Bambu Labs filament? have you tried another brand?
Have you tried PETG-GF? I tried it this past week, and I am absolutely happy with the results.

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The problem with PETG is that it likes to string. If flow is even slightly too high, that stringing will build up blobs on the nozzle, which at some point will be deposited on the print. The next time the nozzle comes around to that spot, it snags on the booger. If it’s at the top of a tall print, it will knock the print over. If it’s in the first few layers, it’ll rip up the plastic off the build plate.

Your problem is flow. Maybe temperature. Both being too high.

I’d brute force it. Take whatever you have for your current settings, knock 10ºC off the extrusion temp and reduce flow by a few percent and try again.

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I’d recommend using search button. It was discussed so many times across many threads.

In short - PETG is marvelous material. However, Bambu Lab printers have an absolute allergy in printing it.
Things to do:

  • Use HF nozzles with antistick coatings (i.e. Obxidian, SiC, etc.)
  • Throw into a trash bin Bambu Lab PETG material - they are one of the worst (if not the worst) PETG on the planet.
  • Slow the hell down. BL printers like to go fast which is not really compatible with majority of PETG filaments. Yes, including “HF” PETG.
  • Bump up temps.
  • Check your infill, don’t use crossing infills. Use something like gyroid.
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What plate is this? Why does it look like an engineering plate?

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The plate I’m using in the example is the supertack, but I have this same issue with PEI cool plate and textured. Indoor humidity is about 40% give or take 4% these days.

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take the textured pei… never had any issues in 3years

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I agree for the old BambuLab PETG basic, which has been discontinued quite a while ago. But the new PETG HF is excellent in my opinion. I have tried many other brands and I always return to BBL PETG HF, because of the good consistency, quality at high speeds and the beautiful surface finish. With high flow nozzle, even 40 mm³/s give consistent good results.
Most others I have tested, had problems with gaps close to the seam at default speeds and accelerations, except for BBL. Not even talking about higher speeds.

To me the flow looks quite good in the parts that stayed on bed. But it is certainly worth watching the printer and look out for buildup.

Do you clean the plates with anything other than water and soap? Especially IPA is not as efficient as one would think.

Is the engineering plate? If so, old or new one? I would also test a PEI plate instead.
For PETG, I now have settled on the FYSETC CryoNix plate. It is super cheap, has very good adhesion when hot and a fine matte texture.

Edit: Sorry, didn’t see that you already mentioned the plate. It really should work without problems with the plate types you tried already. Something clearly is wrong.

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If you printed PLA right before PETG this might cause some problems because these two materials do not stick together.

I would try:
-flush your nozzle to get rid of remaining PLA
-clean your buildplate with dish soap and water (not only iso)!

I use the textured plate with PETG and have no problems. I use one side for PLA only and one side for PETG only to avoid any contamination of the two materials.

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I’ll echo the call to clean your plate with dish soap and water, followed by IPA.

Also, you mentioned higher temps, but I’m not sure if you meant filament or bed temps. I had some trouble with adhesion printing BBL yellow PETG HF on a regular Textured PEI plate, until I bumped up the bed temp from 70 to 75 degrees - then it adhered and printed perfectly. This was on an X1C too. All other settings were default.

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dépending on the chamber temp, I need to rise the bed temp a bit or not.
ie : first print on a cold day, I raise the bed temp to 75°C or so, while most summer days I can start the printer and send a print with default settings
(BBL PETG HF, or any other make : Tinmorry, CC3D, Jayo…)

edit to add the details on room temp :
winter room temp is about 14°C (0°C or so outside here)
summer room temp is about 22°C, top I’ve seen was 26°C with several hot days in a row

all prints are done on and old engineering plate (the one recognized by the firmware)

the X1C is in a separate building, and I 've come to check the temp before sending any print, and raise the bed temp to 55 or 60 , and hot end to 45 before heading there and start a print

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My winter shop temperatures are similar. I deal with it by increasing chamber temperature. Preheat the chamber with the heatbed for 10-15 minutes before starting the print. Running the auxiliary fan helps circulate the heat. Once the chamber reaches about 25°C, my usual presets for nozzle and heat bed temps work the same as in the summer.

I actually found an automatic solution in G-code for X1C chamber heating and heat soak. It does require OrcaSlicer, which means using Bambu Connect or LAN-only mode. (OrcaSlicer supports use of the chamber temp sensor on the X1C, but Studio does not.) The extra Machine Start G-code checks the temp, and delays the print until the bed has raised the chamber to the desired minimum temperature. For high-temp filaments like nylon and ASA, the code can also allow more time to heat soak the chamber.

The real advantage to me is that I don’t need to preheat the chamber manually, then wait and monitor chamber temp before actually starting the print. I just print everything with my modified printer preset - it does nothing extra in the summer, it heats the chamber to a typical room temp in winter, and heat soaks the chamber to a higher temp when the filament preset requires it.

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I print BL PETG-HF using a normal (Not HF) nozzle, default petg-hf profile in bambu slicer and a frostbite plate. I get a little warping at times on larger pieces, but otherwise it works great. Also printed some creality petg again with no issue. I told the slicer it was bambu petg. I did get some stringing with petg from 3DJake and a .8mm nozzle though.

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thanks for the link, I’ll have a look at it : it seems as usefull for me as it is for you

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The only time I’ve had issues with petg is when it’s moisture content goes higher than 15%. If my AMS shows above that, I’ll dry my desiccant and material and I’ll have no issues. I use petg almost exclusively anymore in my x1c.

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You’re just blowing air during the first layers.
Exhaust, Aux must be ZERO and no part fan for at least 3 layers, then part fan no 100% but more 40-50% and front door open.

after X layers you can close the door and set exhaust at 30%

Depending on your device you could need to shut off exhaust one at the beginning of every print (H2D for sure)