I designed this spool holder in Solidworks based on some other designs that I saw and could appreciate various features of. This Design is meant to mount on the 16"x16" interconnecting pegboards they sell at HomeDepot made by Everbilt. This design has multiple fixed slots for the bearings so it can accommodate very small spools all the way up to the monster spools that Prusament comes on.
08/20/2019 - Added RetroFit_Retainer.stl - this piece can be printed and fit over the end to prevent the tubes from pulling forward. Alternatively you can use a small o-ring on the tub that will fit in a groove. Again - designed to print without support.
Print 3X Spool_Peg.stl and 1X Spool_Holder_Prusa.stl
Filament Used: https://amzn.to/2ZeRdRm
The parts should all be oriented so they lay as shown in the printed parts picture. Failure to do may result in inadequate strength or parts breaking when they snap together. This is designed with close tolerances (0.05 mm) between the parts and to fith the pegboard tight and with a positive click once it's through. Removal from the pegboard may be difficult unless it's removed from behind.
Once printed and mounted place a bearing in the slot nearest the back and one in the slot nearest the edge of the spool and slide the rod through. Note this utilizes the skate bearings and tubing that comes with the spool trays with the MMU2s.