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We've been doing some printing with PETG filament on Ender 3 Pro printer and the result were awful: Overview of failed PETG prints

Here are settings we used:

  • Extruder: 240 °C
  • Bed: ~70 °C (± 10 °C)
  • Speed: 80 mm/sec

There are a few types of problems that we had:

  1. Initially filament did not stick to the bed - those 3 items in the middle of the picture are example of this issue. This got fixed by increasing temperature of bed to 80 °C.
  2. At some point a piece would get dis-attached from the bed and would move around together with the extruder around - two prints in the upper right corner of the picture were cancelled for this reason.
  3. Models are very rough, like a cheaply made snowball - that tiny model in the upper left is suppose to be a cattle-bell. Could you tell?

Additional info

Filament that we used indicated

  • extruder temperature 230-240 °C
  • printing speed 40-90 mm/sec
  • no info about bed temperature

Question(s):

  • What are some optimal, tried and tested options for printing PETG? (Temperatures, speed, etc)
  • What are some caveats/difficulties of working with PETG to look out for? (For example, I've read that PETG likes slower speeds. Is that true?)
  • Is it possible that the model of 3D printer does not work well with this type of filament? (I don't have much experience printing so I can't know)
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  • $\begingroup$ Are you using the correct filament diameter, it looks as though it is sparsely filled? $\endgroup$ – 0scar Jun 17 at 18:44
  • $\begingroup$ @0scar I don't know the answer, yet. Another person set things up, I am just slowly trying to learn this stuff. $\endgroup$ – whatever Jun 19 at 14:38
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Slow down!

80 mm/s is much too fast for PETG. Try 45 or 50 mm/s instead, even for infill, supports, and other less-visible areas.

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  • $\begingroup$ Thank you, I will try this. $\endgroup$ – whatever Jun 19 at 14:39
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The Ender 3 can print PETG just fine - even better results than with PLA in my experience. But you do need the right settings. 230-240 °C is too low, especially at the extremely high speed you're trying - you're going to get serious under extrusion and likely stringing.

My PETG settings are 80 °C bed, 250 °C hotend, and normal 30/60 mm/s speeds (probably could do 60 mm/s everywhere if you're okay with lower surface quality), and lowering fan speed to 40 % or lower. Full speed fan will prevent bonding, and is not needed to avoid warping like it is with PLA.

Also make sure you have the first layer set to print slowly (30 mm/s or less), and make sure your gap between the nozzle and bed isn't too wide. You also need the nozzle to be primed well before the actual print starts. A skirt can do this but I prefer custom start gcode to print a thick priming line at the edge of the bed. Mine is based on Ultimaker Cura's default but only goes one direction rather than reversing and moves a lot slower.

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  • $\begingroup$ I see you accepted this answer - did it solve your problem? $\endgroup$ – R.. Jun 18 at 17:59
  • $\begingroup$ I haven't gotten a chance yet to test this, but, regardless of whether these settings will solve my problems or not, for now this answer provided the most information. Is that a wrong reasoning to accept answer? I was planning to come back and update this page with responses when I test this. $\endgroup$ – whatever Jun 19 at 14:35
  • $\begingroup$ @whatever: I'm not sure. I think I answered your three bullet point questions satisfactorily regardless of whether the answer ends up working well for you, but I normally upvote when an answer does that and accept it once I've confirmed that it also solves my problem, since I may prefer to accept a different answer that solves my problem better. $\endgroup$ – R.. Jun 19 at 15:52
  • $\begingroup$ Ok. I took vote away, for now. I'll revisit this page after testing things. Thanks. $\endgroup$ – whatever Jun 19 at 20:53
  • $\begingroup$ Also: waiting to accept avoids discouraging other people from answering, which is good to avoid in case the first answer you like turns out not to solve your problem. $\endgroup$ – R.. Jun 19 at 21:01
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None of your prints look like they are sticking well to the bed. You didn't specify the bed material. For many bed types, you might have success with Aqua Net hair spray.

Like any material, if it isn't solidly sticking to the bed, the print won't be good.

This probably is not related to your problem, but you may need to reduce the drive gear pressure or "pinch" of the filament. PETG seems to be softer than PLA or ABS, and I've had problems where it was rolled out like pie crust by the filament feed gear to the point where it would not feed. Reducing pressure, reducing retraction, and increasing the minimum extrusion between retractions helped.

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  • $\begingroup$ Ender 3's stock bed is a buildtak clone and works great with PETG. $\endgroup$ – R.. Jun 18 at 4:42

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