Here is an alternative to the already existing Scalar spool holder.
This model is using a M8 threaded rod as central rotation axis.
It's also using 2 UFO (cone) shape like parts that will stabilize your spool.
Inside the UFO, cone shaped parts you will need 1 608ZZ bearing that will couple the static M8 threaded rod with the moving spool. The bearings should snap inside properly and depending on your printer resolution they can even stay in place without using the cover parts.
You will also find 1 part that is designed to make sure that the beartings stay in their location. You will need 3 M3x8 or longer screws.
The M8 threaded rod holder is designed to hold on a 3030 aluminum extrusion.
3D Modular Systems
Evolutive 3D Printers
You enjoy it and want to help us with a donation: https://www.paypal.me/3DMS
Easy print here, the support is already included for the UFO shape part.