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Recently I got a PETG filament from Filatech to print with my HyperCube printer with E3Dv6 clone Hotend. First 3 layers for every print are pretty fine but 4th layer doesn't stick and my prints fail like the picture below:  fail

I use the following settings:

  • Slicer: Cura with Generic PETG profile
  • Hotend Temperature: 240 °C
  • Bed Temperature: 70 °C
  • Fan Speed: 100 % at the second layer
  • Print Speed: 50 mm/s (first 3 layers @ 30  mm/s)

I also tested 225 °C and 250 °C hotend temperatures. Both failing at the 4th or 5th layer. What is the issue here?

BTW I successfully printed with ABS and PLA with this printer.

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    $\begingroup$ PETG doesn't like to be cooled at 100 % fan speed. If it cools too much it won't stick (well) to the previous layer. When does the cooler fan kick in? I suspect after the 3rd layer. $\endgroup$ – 0scar Jan 27 at 8:02
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    $\begingroup$ Please add to your question when the part cooling fan kicks in at 100 %. $\endgroup$ – 0scar Jan 27 at 8:15
  • $\begingroup$ @0scar Added print speed and fan start layer. Now I think it might be related to both fan and print speed. 3 first layers print with 30 mm/s. $\endgroup$ – hamidfzm Jan 27 at 8:37
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    $\begingroup$ 50 mm/s is about the upper limit of PETG for my filament with a E3D v6 @ 240 °C. I get better results with slightly lower speeds. I'm in the process of fitting an E3D Volcano to increase print speeds as I'm using 2.85 mm filament. Try lowering the fan speed first. $\endgroup$ – 0scar Jan 27 at 9:01
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As this is material dependant, you are facing not a printer, but a settings issue: your slicer needs the right settigns to print PETG.

The first layers look good, but then we get signs of stringy printing. Stringy printing usually happens if the filament comes out of the nozzle too cold (I had tried to print PLA at 170 °C and it would look somewhat similar) or if it gets cooled or stretched too much (forced a print failure by speeding up a 60 mm/s print, somewhat similar around 250-300%; though the filament was not hot enough then too). This, in conjunction with the information, that you print PETG suggests the following things to fix:

  • Reduce or deactivate cooling. PETG often doesn't need cooling at all.
  • Reduce print speed. As 0scar said, 50 mm/s is a good upper limit on a well honed in machine. As your other layers with 30 mm/s were fine, you could possibly go down to 40 mm/s, if less cooling alone doesn't help.
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  • $\begingroup$ Is the speed recommendation based on volumetric extrusion? For example, 60 mm/s and 0.6 mm extrusion width is equivalent to a 80 mm/s with EW 0.45 mm. $\endgroup$ – FarO Jan 27 at 12:40

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