PETG jamming in extruder gears after ~15 minutes - K2 Plus

Flagship K Series Creality Flagship K2 Plus & CFS
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1

Hello,

I have a Creality K2 Plus Combo (firmware 1.1.4.11) and I’m having a consistent problem when printing with Creality Hyper PETG using the stock filament profile.

Problem: After about 15 minutes of printing, the filament softens and jams between the extruder gears. The printer cuts the filament cleanly but the softened PETG gets stuck inside the extruder housing.

Details:

  • Happens only with PETG, PLA prints fine

  • Happens specifically on solid/flat surfaces (large infill areas)

  • Stock Creality Hyper PETG filament

  • Stock filament profile (no custom settings)

  • First layer is perfect, no adhesion issues

  • Tried multiple models, same result every time

Question: Has anyone solved this specific issue? I see many posts about PETG problems but none with exactly this symptom — softened filament specifically in the extruder gears, not in the heat break or nozzle.

2

Did you check the chamber temperature when the softening happens?
Maybe try to print with a the generic profile to see if there is any differences?
Do you have other rolls of PETG to try, so you can exclude that it is this specific roll of filament that is giving issues?

1 Like
3

Hi, try to reduce the printing speed, switch to 50% or “silent” mode. If it helps, change speed settings at slicer for current filament. And make all calibrations: temperature, flow rate , PA, ..) for best results.

4

It’ll be interesting to see if this helps you. On this K2+, the extruder motor is always at 100% power, so gets fairly hot at idle, which couples into the filament rollers and leads to the dreaded soften and jam.

Try this. On the Axis/Temp screen or in the Fluidd interface, press the MOTORS OFF button. The bed should slowly fall down as all the motors are now unpowered. Leave it sit like this overnight, to allow everything to cool. In the morning, run the print.

If that does not help, a recalibration of the extruder motor may help: Calibrate K2 Plus Extrusion Servo Motor (e-axis motor or extrusion motor) | Creality Wiki

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5

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I have now tested with 3 different rolls of Creality Hyper PETG — all with the same result. So it’s not a filament issue.

The extruder gears were full of softened PETG each time. Already cleaned and ready for next test.

I will try the MOTORS OFF suggestion before printing and report back.

6

After switching to almost exclusively printing with PETG for teh last 3 months I have run across this problem many times.

I finally solved mine by “increasing” the nozzle temperature and now run at 260C for black PETG while for white I use 265.

Reducing the flow slightly also helped, do a Flow rate calibration within the slicer. Mine was 0.95 and I now used 0.92

I haven’t had a single extruder blockage since doing these two things

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7

My technician told me to leave the door open when printing PET-G and I was skeptical, but worked!

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8

But why would PLA print fine with door closed and petg not?

9

Update: Problem solved!

I didn’t change any slicer profile — I used the default Hyper PETG profile as-is. The root cause turned out to be that Fan 1 (chamber fan) was not enabled in the profile at all, so it stayed at 0% during the entire print.

With the bed at 70°C and Fan 1 off, the chamber temperature slowly climbed and the extruder gears area got warm enough to soften the PETG filament (~75°C softening point), causing it to jam between the gears.

Fix: Simply turn on Fan 1 to 100% at the start of the print (via Fluidd or Creality app). Chamber temperature stabilized at ~33°C and stayed there for the entire print.

Test results:

  • 15 min: no jam (previously always jammed here)
  • 40 min: no jam
  • 1 hour 7 min: no jam
  • Full print completed successfully (~4.5 hours)

So the fix is just enabling the chamber exhaust fan in the PETG profile. Creality should probably enable Fan 1 by default in the Hyper PETG profile to prevent this issue for other users.

Thanks to everyone who helped, especially @rdtsc for pointing to the motor/heat issue!

3 Likes
10

Excellent, so the problem where not happening with PLA because the fan was enabled on that profile?