After several tests I came to the conclusion that my 23 cm x 23 cm wide piece was impossible to print due to the rubbing of the PP filament (used external spool), because when the print head was in the right corner where the PTFE tube reached the maximum torsion, the PP filament was no longer dragged and the dragging mechanism began to trip compromising the print (Clog).
I think they need to find a more streamlined and direct method of dragging for these materials, otherwise it will be impossible to print them despite the closed chamber and using the external spool.
PP Natural Filament - Form Futura
PP General print settings, adapted with improvements found on the net.
I want to try to insert the filament from the lid directly without PTFE and see if this will allow me (even if the lid is not closed) to print my PP piece.
Do you have any other tips or tricks?
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It’ll be tricky due to warping/curling resulting from the open lid.
If it is borserline, it may be worth a try to reduce external spool friction with a ball bearing external spool adapter (I use the one from thrutheframe on MakerWorld) and minimizing spool weight by repsooling just a little bit more than you need onto an empty spool to minimize drag.
Other than that: Good Luck 
Have you tried a tad longer PTFE tube and larger ID tube?
BBL PTFE tube is ID2.5mm. There are PTFE tube with ID3.0mm and OD4.0mm
Thanks to all of your solutions and opinions.
However, I believe that the main cause is precisely the impact of the PTFE in the right corner where the tube creates a torsion on itself and therefore increases the rubbing of the PP inside it.
I’m already using a spool holder on bearings.
By lengthening the tube the path increases, I should try with a larger diameter…
I think I’ll do the direct wire test anyway and I’ll let you know how it went…
Best regards
luca
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