Grip for Soda Stream bottle cap (or for other things!)

This is an add-on grip for the original Soda Stream plastic bottle caps.
The original cap is super slick and it's really hard to open with even slightly wet or oily hands.
I designed this grip to be printed with TPU and to be press-fit, keeping the rubber seal and water tightness of the original cap.

This grip can be used on other cylindrical things! It's customizable! :)

• This can be printed with other materials and glued onto the original cap. But before printing it in non-elastic material, you need to adjust the diameter in the FreeCAD file and export again.

Assembly

Before assembling clean up any nubs or blobs that might have formed on the inside.
Clean and degrease both parts. The grip on the inside and the cap on the outside must be clean, dust free and degreased.
Put the cap back on the bottle, then firmly press the grip onto the cap. For better results you might want to press the bottle upside down at a slight angle against hard surface while rotating so the grip sits down against the top of the cap.

If the grip slips when torquing down the cap, adjust the fit in the file and re-print. Alternatively, if you don't mind making it permanent, use CA glue.

Designed in FreeCAD

I designed it using FreeCAD, entirely in "Part" workbench. Almost all dimensions are parametric and can be changed in the original file I provided.