Goodbye pneumatic connectors!

I've found in my experience that pneumatic connectors are actually terrible for bowden style 3D printing (its almost like they were designed for something else!). They allow twisting, which chews up the PTFE tube, making a notch (see image) and adding play in the system, severely increasing retraction needs.

By getting rid of them I was able to reduce my optimal retraction distance from 7.5 mm down to 1.6 (and thats with a 50 cm long bowden tube).

My design screws into a (standard?) BSP 1/8'' 28tpi thread and uses a set screw to lock the tube both axialy and rotationally, minimizing any wiggle room for the filament. The screw I used is 2.5 mm in overall diameter and 5 mm in thread length. Any screw you use must not stick out too much into the tube, otherwise it will restrict the sliding of the filament (see amount of stick-out needed in picture below).

If you are not able to find similar screws to the ones I used, I also included .f3d and .step files you can modify to fit yours.

I recommend printing at 0.1mm layer height and you might also need a brim for adhesion. I also suggest cleaning up the hole with a 4 mm drill bit.