PTFE Tube Cap with Retainer (TPU)

Cap for sealing 4mm PTFE bowden tubes (for 1.75mm filament), with a tether / retainer to prevent misplacing. It aims to block moisture from getting into a dry box or AMS, or dust from getting into the tube.

The standard design is optimized to be sleek and unobtrusive, while still comfortable to use.

The versions with a long tether are recommended if you tend to take the cap off with some urgency, and find yourself yanking the retainer, or if the cap is touching the filament.

The versions with a deep/long cap are intended for dry boxes with a tube fitting, for which you'd like a length of filament sticking out of the tube for easy grabbing, or if the standard cap is too small to grab comfortable.

I personal use the standard variant for the AMS junction, where filament is only fed in, and the variant with a long tether and a medium deep cap for dry boxes with a tube fitting and filament sticking out for grabbing. If you still struggle to grab the filament, you can try the extra deep cap.

The retainer has some width to it and is a little tighter than the cap, to minimize the chance of it coming off when removing the cap. The cap has an inner taper for easy placement.

It is designed to be printed with a flexible filament — I used (slightly too wet) Overture 95A TPU. I suggest pushing a piece of scrap PTFE tubing through the retainer and into the cap, to clear any stringing before mounting it to your setup.

I print these with all walls or 100% concentric infill (usually effectively equivalent), but suggestions are welcome.