Modular Filament rack with low profile casters
Works really well for maximizing storage capacity in limited space.

This model is based on
Filament Spool Rack - Stackable - Gluelessby ihateu3
Glue-less dovetail joints on the original design is a great feature.

Added features:
Flatten Bottom of the frame to add 1" ball casters.
https://www.harborfreight.com/1-inch-roller-ball-bearing-67060.html

Casters are secured by #8x¾"length Teks screws or equivalent #8 ¾" length self tapping screws.

Redesigned upper frame to add extra tier with less material.
End caps are optional for finished look.

As the original design suggests, use 1/2 " EMT electrical conduit for bars.
I cut them for 28.5" which make a rack hold 10 SUNLU filaments per tier.

The one described in above holds 30 spools.
You can add extra tier to go taller, cut EMT conduit longer to make them wider or both.
If the space is extremely limited, you can make them single tier and narrow also.

You can adjust size of filament rack to whatever suit your need.

Instruction:

• You need to print 2 of each frame components plus 4 dwells and 12 end plugs to make a complete set of rack.
  
• If you are not using casters, print extra middle frames instead of the bottom ones. raised bottom keeps rim of spools from touching the floor.
  
• PLA, PLA+ or PETG would be sufficient for this model
  
• Minimum 4 wall thickness and infill 25% or higher.
  
• No glue required. Tap frame pieces together with rubber mallet.
  

Happy Printing!