Hello everyone, 
After several weeks of testing Bambu Lab’s PETG filaments, I can’t seem to find the optimal settings to get my prints right every time.
Background:
A few months ago, I bought 2 spools of Bambu Lab PETG filaments (white and blue) at the same time as an X1C printer.
Being a beginner in 3D printing, I started by printing PLA from Bambu Lab and other brands, respecting the recommended parameters and I had no problems.
I then tried printing PETG parts and that’s when I started having problems.
Problems encountered:
As you can see from the first photos, I had several problems:
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Filament sticking to the nozzle (without clogging it);
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Plastic crumbling and getting everywhere on the platen and in the printer casing;
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Filling defects that could end up causing major structural problems and stopping the print run;
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Defects in the outer layers.
When I had these problems, I used the printing parameters recommended by Bambu Lab for their own filament. I was also printing with the front door open and the top glass window slightly ajar.
Filament testing:
Following these problems, I tried to find solutions on this forum and the items that came up most often were filament printing temperature, ventilation and filament humidification.
First, I disassembled the nozzle to clean it, then I tried to find the right settings for my filaments. To do this, I printed out a temperature tower and a ventilation tower. I then realized that increasing the temperature beyond the recommended parameters, i.e. >260°C, gave better results. Similarly for ventilation, the best results were obtained at speeds >90%.
Imposing a print temperature of 270°C and 90% ventilation, the blue filament printed perfectly, as shown in the photo below, which compares Bambu Lab’s default settings for their Basic PETG (right) with the new settings I tried (left) :
However, this was not the case with the white filament.
As I could hear bubbles popping when it was extruded, I proceeded to dry the filament in a dry oven at 65°C for 8 hours. After the drying, the filament was finally printing properly.
At this point I thought I’d found the right parameters to put the problems behind me. Unfortunately, 3 weeks later I tried to print a part with the blue filament and I had the same problems as in the beginning (filament sticking to the nozzle, filling defect, etc.). As I hadn’t dried it, I thought the filament might have hydrated, so I spent 8 hours at 65°C.
After that, the filament finally printed correctly.
At this point I thought I’d found the right parameters to put the problems behind me. Unfortunately, 3 weeks later I tried to print a part with the blue filament and I had the same problems as at the beginning (filament sticking to the nozzle, filling defect, etc.). As I hadn’t dried it, I thought the filament might have hydrated, so I spent 8 hours at 65°C, as I had done with the white filament.
However, as you can see from the last photo, this didn’t solve the problem and I still can’t print properly with this filament.
Conclusion:
I don’t know how to print PETG properly. I wouldn’t dare recommend it until I’ve figured out how to print it perfectly with the X1C, but I’m at a loss at this stage.
In case you’re wondering, I store my reels in Bambu Lab’s AMS, which gives me good hygrometry.
Thank you for taking the time to read my long message so far, and I’m grateful in advance for your help. 
Léopold
