Dual extruder stops to extrude

I am slicing the same file with luban 4.5. when using Normal or Fast profile all good, when using Smooth surface my dual extruder stops extruding. it gets badly stuck, like heat creep problems. There is a clog in the tube inside the heath sink on the hot end. cannot manage to get it out even using the hotend controls from the display.

emblemmagic v4_normal.gcode (981.7 KB)
emblemmagic v4_smooth.gcode (2.2 MB)

Attaching a picture of the tube inside the hotend with the filament stuck

The filament measures 1.73

But inside the tube becomes 2.10 which then doesn’t let it go out either ways.

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I had the same problem with some filaments. No solution yet.

Hi same problem for me only try with fast setting and for me the problem it s only on the right extruder i allready try 2 different filament 2 different hot end and the standby temperature at 75. I test to make a retractation at 40 mm when switch it s clogged again but not need to unmount the hot end for fix it.

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Did you check that both heat brake cooling fans are running? Perhaps one is faulty, or the firmware and/or Luban has a bug that “forgets” to switch the fan on under some conditions…

Btw.: I think the last picture in your post is the wrong one (some as the picture before) - if you don’t mind, can you post the correct one?


Changed the default settings in Luban to have standby temp at 75 (retraction I still have it at 1mm) and so far I managed to get slow prints to work too.

Did anyone try to replace PTFE tube with one with smaller diameter? If the problem is that filament expands into it’s inner diameter of 2mm and than can’t fit into brass connector.

Or maybe i can try to drill bigger opening into the hotend?

I fix my problem with termal past inside the hot end

Unfortunately this does not seem to fix the problem for all - I have no success. Discussion is ongoing here: Dual Extrusion Head: Heat creep? More likely: Bad feeder! OR: bad heat break to heat sink connection --> use thermal grease! - #60 by Hauke

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I printed a front cover with a hole in to allow air flow directly on the hot end.

Did it help?

Yes, it has helped. I have been able to print 2 color parts. It’s shown with an exterior fan, but I found you don’t need it. The magnet I have mounted isn’t very strong and should be replaced with a better one.

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So you say it’s just enough to have a hole in the front door to let more air in?

Yes, The hole appears to be enough. I measured the temperature on the cool section and it was about the same with and without the fan. The internal deflectors make the air go across the fins. The original air flow was from the top of the head and doesn’t cool adequately.