Really racked my brain for awhile on how to pass the filament through the roof of my Lack enclosure. I was using this 3-piece design for awhile and hated it, it was a massive pain to load filament through and caused unnecessary strain on the extruder. I eventually came up with this simple design. The screws were out of my miscellaneous hardware bin, but I doubt it'd be too hard to find something that will thread into the plastic if you take electronics apart.
Print two clamps, I believe I printed them in a 0.12mm layer height. I used the shorter tube on the top coming down, with the longer tube on the bottom.
Drill a hole straight through the top of your enclosure that's at least smaller than the collar on the printed tubes. Start on the top with your PTFE tube and pass the bottom side through the first clamp and then the short tube. Press the long printed tube up from the bottom and feed the PTFE into it. Leave as much or as little tail as you like on the inside and put your second clamp on the bottom.
The author marked this model as their own original creation.