Ender 3 Max Neo stops printing after 2-3 layers - blocked & buldged fillament

Ender Series Creality Ender-3 Max & Pro & Neo
1

Hi there,
after some pause from printing (made some small prints a year ago) and installing new PETG I’ve managed to successfully print.
On the second print, I’ve got blockage. I’ve replaced the nozzle, cleared the tube, checked that it is cleaned by pushing it through.

Then, I’ve tried to print PLA benchy. It was fine till the “roof” it began stringy and didn’t stuck.
This was “original gcode”.

I’ve changed then again to PETG and tried multiple thing in slicer:

  • vent to max 20 %
  • temp to 240 °C
  • bed 80 °C
  • retraction 5.5

Printer was working fine before and had occasional bed adhesion issues. Now glass adhesion is good (clean surface, leveled bed, z offset was a little bit low I’ve changed this).

I though it was a too-strong force on the extrusion lever (spring tension screw). I’ve losen it.

After print fails i can see that end of the filament is buldged and some biting marks from extruder.

When next print starts there si no issue (filament inserted) so I rule out that it is clog in the tube but the next print fails on level 2 or 3. It starts to look like the lines are “thinner” and it doesn’t stick so the extrusion stops.

I’m not sure is it hardware issue or a slicer issue or a combination.

Does someone have an idea what I should try next?

2

Ok, so I guess it was a problem with the original tube and (importantly) heatbrake.

I already had parts lying around—a replacement tube and a bi-metal handbrake—so I replaced the original with new parts.
Then I noticed the wire to the front fan (heatsink cooler) had broken off. It probably happened while disassembling the parts. I’ve resoldered that.

I think what happened is that with original parts with higher print temp (PETG @ 240˙C) it melts too much material in the tube. As retraction is pretty big this gives the opportunity to harden some filament up in the tube and then I’ve got under-extrusion and eventually clog/printing stopped. This could be seen as “thicker” plastic at the end.

I have neo and now with upgraded heatbrake (critical part) I print with lower retraction level. Still experimenting but 3 - 4mm retraction seems to work.

So If anyone has a similar issue I would highly suggest getting upgraded heatbrake and tube. Also, check your fan as this can cause the same issue.