UPDATE 3/1/2022 - I've added a couple of feet models. These are optional but should help your shelf stand with more stability. The feet should fit snugly in the bottom holes but you can add glue to really secure them there. If printing the normal foot, make sure you have a decent amount of infill to prevent the top rod from shearing off. The "stronger" foot design is more secure, so it should be stronger (obviuosly) and yet not require as much infill.

This is a redesign of my my .5" Dowel Filament Spool Bracket. I wanted to engineer something that looked a little more refined, and could be printed in less time with less material. I kept the intent of the original bracket, making it symmetrical and stackable to allow you to create a customized multi-level rack of any size by adding more brackets and 1/2" dowels.

The dowels are spaced about 5.5" apart, and can support typical filament spool sizes, such as 1kg(8"), 500g(6.5"), and 200g(5.5").

I suggest printing it flat so that the bracket will be strongest where it is supporting the dowels and the weight of the filament. The tolerances are tight, so if you don't want to sand the dowels or file the holes in the bracket, you may want to resize it to 102%-104% when slicing/printing. No glue is necessary, but it might be a good idea if you plan on making a long rack that spans multiple dowels.