This was a request by a user here to make my spool holder without the need for any additional hardware.  After some serious testing I came up with this all 3D printed design.  No bearings but the spool holder slides over the axle and a friction fit cap holds it all in place.  The spool holder has very little friction and the filament unloads very smoothly.  You could add a very small amount of synthetic grease on the rear of the hub, but I didn't need it. 

I've also discovered a second benefit of this setup.  You can print extra spool holders, then it becomes a quick spool change setup.  Simply unload the filament, remove the end cap, and slide the entire spool off.  Next, having a second roll of filament with additional printed spool hub, simply side it in place and reinstall the cap and load the filament.  No having to remove the outer spool nut swap spools and re-install the threaded nut.  Works a treat as the saying goes.

I printed two of these, the first in PETG and 2nd PETG-CF both printed great.  Note: The 3MF file has 4 plates, I suggest printing the taller parts separately.  There is a large 2mm thick washer that must be installed between the printer and the spool holder this adds additional area to help to make the the part even more stable. 

Happy Printing M1