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Printing Colorfabb XT-CF 20  

Eminent Member
Printing Colorfabb XT-CF 20

Hey guys,

i am desperately trying to print carbon fiber filament, to be precise Colorfabb's XT-CF-20. In every print after some perfectly fine layers the filament stops extruding. Sometimes it's after 10 minutes, sometimes after 2 hours. I switched from .4 mm Olsson Ruby to a .6 mm hardened steel nozzle to see if the larger diameter helps but the error stays the same. 

Apart from the .6mm nozzle my settings are: 
Temp: 255/70
Fan: 50%
Speed: 45 mm/s - 70 mm/s at .3 mm layer height (Quality Setting for .6 mm nozzle in PrusaSlicer)
Retraction: 1.4 mm with 40 mm/s

I kept the settings pretty much as is when choosing a PET(G) Filament in PrusaSlicer apart from a higher temperature.

Any tips on how to print this stuff? I love the looks and the mechanical properties of the material from what i was able to print, would be sad to "throw it away".

Thanks in advance.

P.S.: I am using a MMU2S but as this shouldn't affect the error i posted in the more frequented forum.

Posted : 21/07/2021 11:11 am
Eminent Member
Topic starter answered:
Additional Information

In addition I might add that I just tested with much slower speed (max. 30 mm/s) and the result is the same. 2 hours into the print the filament stopped being extruded. After stopping the print i always have to use significant force to unload the filament by hand, MMU is not strong enough.

I have 2 more theories after being sure about the nozzle being large enough: 
1. The filament was laying open for too long and is too humid. Does this cause this kind of failure?
2. The stepper motor is HOT. Could it be that it runs too hot? I'm printing in an enclosure, temperature inside is about 35-40 °C. I am not sure about this since I can do 20+ hour prints with other filaments without having any issues.

What do you think?

Posted : 21/07/2021 5:33 pm
Noble Member

Have you tried a cold pull?  You are printing at relatively high temperatures so any residues of previous filaments might have baked in causing a partial clog.


Posted : 22/07/2021 10:09 am
g monkey
Trusted Member

Try using the standard Prusaslicer profile for XT-CF20 and not enclosed (have the doors open at least).  I've not had this problem with this filament, but I was using a tungsten nozzle with no enclosure.

Posted : 22/07/2021 9:24 pm