Due to my other design, (found here: https://makerworld.com/en/models/97332#profileId-103873) using a fair amount of support filament I created this design with a triangle pattern in the center area. It can be printed upside down requiring only a small amount of supports for the inside of the post holes. My tests showed the holes on the side held their shape perfectly.

The end result, ironically, uses more filament than the other design but that is due to the triangles spanning the width of the brace creating a stronger part.

Print as many middle parts as necessary depending on how many levels you would like and print the braces if you are extending the length of the shelf rods longer than approximately 30" or 76 cm.

It was designed for ¾ inch dowel rods. If you need something other than ¾ inch simply add a negative part in the slicer and make the hole .15mm larger than the size of you dowel rod so it will fit nicely. You may want to make a test part prior to printing an entire frame piece. The vertical rods are 196mm which provides a small amount of clearance for a 200mm spool.

Use #6 screws to fasten the frame to the rod. I recommend at least a 20mm or 1" screw length.

Update #1: Added new profile with thinner triangles for less filament use.

Update #2 No updates to these files but have created an adapter system for using small spools.

Small Spool Adapter:  https://makerworld.com/en/models/192133#profileId-212217

Assembly Video