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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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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. $\endgroup$ – wha7ever Jun 19 '19 at 14:39
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The Ender 3 can print PETG alright - in some regards, such as warping and adhesion issues, even better than PLA. 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 40 mm/s print speed for everything, and lowering fan speed to 40 % or lower (ideally off entirely unless you find you need it). 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've read in a few places that the tubing for the Ender 3 can't handle 240c, let alone higher and will start to release toxins. Did you replace the tubing with a higher quality one? $\endgroup$ – John Dec 9 '19 at 7:54
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    $\begingroup$ @John: No, that's just kookery. Teflon doesn't even start to break down until over 250, and unless you get a lot hotter the amount will be minuscule. Your cookware gets a lot hotter anytime you burn something. These are the same folks who tell you you're going to get cancer cooking with nonstick pans. $\endgroup$ – R.. GitHub STOP HELPING ICE Dec 9 '19 at 12:08
  • $\begingroup$ Also there is no "higher quality one" I'm aware of, in terms of durability to heat. (Someone please chime in if I'm wrong on this part.) There are higher quality ones in terms of dimensional accuracy of inner diameter, surface smoothness, etc. $\endgroup$ – R.. GitHub STOP HELPING ICE Dec 9 '19 at 12:10
  • $\begingroup$ Well I know for sure that above 235c mine starts to omit a very foul oder and is likely melting itself. I don't have the same issues at 230c which I'm now printing my PETG at. I haven't seen a source besides yours saying that above 240c is fine on the ender 3 because they cheap out on the tubing. I've seen the Capricorn PTFE Bowden Tubing mentioned as a higher quality one that will handle higher temps fine without melting itself. Do you have any proof that all the other places are wrong and that that nasty smell is just fine for me? $\endgroup$ – John Dec 10 '19 at 6:26
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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.. GitHub STOP HELPING ICE Jun 18 '19 at 4:42
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The real problem was that I damaged the nozzle (most likely while cleaning it) in a way that increased the size of the hole. So, too little filament was coming out of too big of a hole, which caused such poor models. Replacing the nozzle fixed the problem.

I do not remember the settings of the top of my head. Generally advised settings for PETG (whatever they were) worked fine.

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  • $\begingroup$ How did that happen? $\endgroup$ – FarO Oct 28 '19 at 18:00
  • $\begingroup$ @FarO Probably while I was using scissors-like instrument (I forgot how it is called) to clean up excess of filament that was coming out during warmup. I must have not been careful and cut off a tip of nozzle by accident. I didn't notice while I was doing it. That thing is so tiny. But looking back at what I was doing this would make the best sense. I was also trying to level the bed and used piece of paper to determine friction. Not sure if that could do any damage to the nozzle's tip (if not done carefully). $\endgroup$ – wha7ever Oct 29 '19 at 13:53
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I just made an account to point out that you will scorch your PTFE tube if you listen to anyone here telling you to print at 250+ C. I have done this, it is a bad idea without an all metal hotend.

Not a lot of dumb things on here will actually give you cancer, but cooking your PTFE-liner will.

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    $\begingroup$ note that the PTFE will start to break down at 327 °C. However, it will detoriate starting at 260°C, which, wich some degrees of safety means you shall not print with a lined hotend at above 250°C. You won't create PTFE fumes till 327°C. $\endgroup$ – Trish May 26 at 18:39
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55 mm per second is the highest I would go with PETG. Cleaning the nozzle more often helps. Also check your PID for the nozzle temp, it could be inconsistent and PETG can be very finicky with temperature.

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