Microcenter / Polymaker Carboard Spool Inner Hub Sleeve

The carboard spools on rolls of filament from Microcenter and Polymaker are great for the environment... but they do not unspool as smoothly from a rod style spool holder as the old plastic variety used to. The spools carboard inner rim causes additional stiction and hence will unwind in a stick/slip motion. This uneven unwind can translate into visible print artifacts. This printed hub can help the spool unwind more evenly.

I have tried to minimize material usage and print time. On my printer the two halves press together after printing with a satisfying fit, but they can be wiggled back apart later when the spool is empty for reuse on the next one. 

I have included the native solidworks 2018 file, the step file, and an STL. So if the dimensions need some tweaking for your application please feel free to modify as you see fit.