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I struggle badly at printing PETG

Anycubic PETG

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Hi there,

I'm printing things with PLA since almost a year now and it always resulted in parts with awesome quality. Now I wanted to try PETG and it's turn out to be a little desaster (please see the pictures).
I printed a few things well with PETG before but I guess the things were not so hard to print.

Currently I'm trying to print this fan case for the i3 Mega power supply: https://www.thingiverse.com/download:4579356
I constantly fail to print a clean first layer. There are multiple problems, it seems: The filament is oozing while the nozzle is traveling which causes the filament to roll up and stick to the nozzle. Then when it comes to the more thin and filigree lines, the filament will extrude too slow and almost nothing will stick to the bed. The filament behaves like chewing gum.
I also have very bad stringing.

I can't help myself anymore - I tried everything:
Adjusted the speed, fan speed, retraction, temperature, z-offset, underextrusion, overextrusion ... well, probably everything.

I don't know whether it's the nature of the .stl or the slicer settings (cura 3.5) or maybe the filament is just poor.

How do you print PETG with the Anycubic i3 Mega? Can you give me any advices? I would be very grateful, since I'm gradually frustrated :-(

Best regards & thank you very much!

Mike

PS: I printed the same model with PLA just fine but the printer also stuggeled there a little bit with the small screw holding parts at first layer.

Hi, I'd like to second all the suggestions below, basically. First, the massive stringing indicates you need more retract and possibly experiment with higher nozzle temps. Turn it up by 10°C, increase retract by 3-5mm and try again. Also turn off the part blower if ever possible to minimize warping effects. That also applies for ABS.

Also, heat up your nozzle and clean it thoroughly.

I have had nice results with a PETG from eSun and one from Kexcelled (if that matters). Hotend at 245C and bed at 80C and as others have mentioned, I too clean the bed just before and make sure it's completely level. E.g. if your bed is a bit too close to the nozzle, you might get those snagging issues.
If I print at low layer heights (0.2 or below) I tend to go with 150% layer height on the first layer. Also, I often use a brim for a bit of extra adhesion.

Hmm, after looking at your pics, it seems your outer paremeters seem to stick down nice enough so perhaps the screw holes in the corners are more of a retraction issue than a bed adhesion one as such? PETG is indeed quite runny and stringy so you need to dial in your temps and retraction settings carefully.
As for the stringing, I did put a direct extruder on my Mega which has really helped but that is a whole other project altogether.

Hey. Tried to turn off the blower model? I print PETG from FDPlast without blowing a model.

I have struggled with PETG as well although finally came out with half decent prints. For me the key was to get the PLA settings perfect, especially bed levelling, this is the system I now use https://www.youtube.com/watch?v=RZRY6kunAvs&feature=youtu.be
Then it's a case of increasing the z height, build plate and nozzel temperatures as well as increasing retraction (This should be down with something like this https://www.thingiverse.com/thing:909901 )
If you work your way up solving each stage as you go you should get there:

  1. Level bed using the levelling squares, adjust as necessary
  2. Clean bed (Alcohol or my favorite, window cleaner)
  3. Dialled in PLA settings that give you the best print possible - test to make sure with a say a benchy
  4. Load in PETG Filament
  5. Z height adjust, bed and nozzle temp - test with the levelling squares, adjust as necessary
  6. Test and adjust retraction as necessary.
  7. Finally ready to print your model

I have been in the process of major upgrades so am in the process of dialling in my PLA settings, once I am happy with those, I will have another go at some of my PETG prints.

Jd

Retraction test