Prusa Research MMU3 Manual Del Usuario página 115

PASO 12 New PTFE tube installation
Now it is time to insert the new PTFE tube. Note, that each end of the tube is
different.
One end of the tube has an outer chamfer. This end must be inside the hotend.
The other side has an inner chamfer. This conical shape is the filament entry. This
part must be outside the hotend.
Push the PTFE tube in. Slide it all the way in and hold it!
Using your other hand pull the collet out while you keep pushing the PTFE tube
in. THIS IS CRUCIAL for the hotend to work properly.
After you finish inserting the new PTFE tube, check that the whole hotend is
tightened up and nothing got loose during the process.
PASO 13 Extruder reassembly (Part 1)
Re-insert the hotend back into the extruder. Ensure its orientation is the same as
seen in the picture.
IT IS CRUCIAL to ensure the hotend is fitted properly in the extruder-body!!! The
top of the hotend must fit into the correct recesses in the printed parts. See the
second and the third picture for a reference!
9C. Extrusor MK3S+ (UPG)
Ensamblaje Original Prusa MMU3 115