This is a modular, stackable filament spool rack system. 

It is expandable and extensible, either by stacking units on top of each other, or side by side. 

Features

• Strong and rigid, but also lightweight.
• Holds any spool that is less than 80 mm wide, and less than 208 mm in diameter.
• Holds most filament boxes and spools inside bags. 
• Specially designed to hold spools while adapters are attached. 
• Very little assembly required. Connectors are used only for attaching one shelf to another.
• All 3D printed parts - no hardware is required. 
• Adjacent shelves attach to each other using a dovetail joint.
• Stacking shelves attach to each other using cantilever snap fit connectors

I buy filament from many different sources, with lots of different types of spools. That often means that I need a spool adapter to make the spool work well with my AMS Lite. But I got tired of attaching adapters, and then removing them. I needed a filament spool storage system that would let me leave the adapters attached. That was the inspiration for this model. 

I attach an adapter, like these universal ones (and the one I designed), when I first use the spool. This rack system lets me leave it attached until I have used up all of the filament. 

Each shelf allows space for an adapter to extend below the spool by up to 16 mm. This should accommodate most adapters. Space above depends upon how wide your spool is, and by the spools you have stacked above it. It is best to avoid adapters that would take up more than 98 mm of vertical space. If you have choices, choose the adapter that is just big enough for your spool, and no larger. 

Any filament that is hard when cool should work. The snapping part of the cantilever snap fit connectors probably won't continue to flex and snap if they are printed in PLA. But this rack system likely won't be disassembled very often, so it probably won't matter. Once each shelf is stacked on the one below it, the cantilever snap fit connectors will hold everything together just fine. 

The print profile includes the following plates:

• Shelf with connectors. If you are planning to do a lot of stacking, this is all you need.
• Shelf alone, without connectors.
• Connectors only, no shelf.