A simple electrical wire spool design that is quite sturdy, features the ability to generate any size of spool, and requires no glue or hardware to assemble.

This improves on the design by Gladius by featuring two cores that mate together to create a stronger spool than the original (which I found tended to break).

I have only tried this with PETG but should print fine with most typical materials. 

Improvements to the generator code can be contributed at https://github.com/mattinglot/wire-spool-generator

Check out the wire spool hanger for a handy way to hang the spools.