Filament cap for drybox with pneumatic fitting

UPDATE: on 05/22/2025, I updated the file for this filament cap with my latest version which works better with a wider range of filaments, from soft TPU to hard/brittle filaments.

I designed this filament cap to replace the one that came with the upside down filament drybox by GunplaMark. This cap address 3 issues I had.

1. Brittle and breaks off if knocked from the side
2. Tends to allow the filament to fall inside the drybox
3. Difficult to release the retainer on the pneumatic fitting

After printing this piece, insert a short piece of PTFE, about 30mm long. I held the two parts with the PTFE down on a piece of wood and the used the butt end of a screw driver to tap on this cap, pressing them together.

This part has “nubs” inside it, on set to hold onto the PTFE, and one smaller set to hold onto a 1.75mm filament.