Print failure due to heat creep

Question

I have purchased a Creality Ender 3 about a year back. Initially it worked flawlessly even with PETG (at 240 °C) but after some time the prints started to fail.

The filament started to expand and clog the hotend. Later I found out that it was due to heat creep. I have tried the below methods to reduce heat creep.

1. Tried bimetallic heatbreak.
2. Applying thermal paste to heatbreak (applied between the walls of the heatbreak and heatsink, small amount)
3. Tried PLA and other brand PETG (as filament moisture may be the issue).
4. Installed direct drive.
5. Reduced the retraction distance to 3 mm.
6. Tried printing with larger layer height.
7. Installed an additional fan.

Despite all the efforts the prints are still continuing to fail. Can anyone suggest some tips to reduce the heat creep. Note: The above efforts have made some improvement. Only prints with printing time greater that 5 hours (approximately) fail.

But initially, It has successfully printed models more than 20 hours print time with PETG (at 240 °C).

Answer 1

With a direct drive extruder, a retraction of 3 mm is quite large. This is typically a value that is used for short Bowden tube remote extruders, longer Bowden tubes even require longer retraction values.

For a direct drive I'd work my way down from a retraction of 1 mm using e.g. a Parametric retraction test pillars model.

A replacement fan, with more flow to cool the hotend, could also be helping to cool the top of the heatbreak preventing heat to creep up further in the cold end.