Having tried many different empty spool based storage systems and creating a couple of varieties myself, I kept coming back to the same conclusions...

I didnt want to drill new holes in the spool, i didnt want to faff with lining up points and risk misaligning the tray axles, I didnt want to add lots of additional hardware.

I did want to print it, all of it if possible, i did want it to be robust so it could carry lots of weight, and i wanted it to stay shut when i shut the drawers!

So i designed this set...

The main axles are outside of the spool body, meaning they are free from alignment and drilling errors.
All the parts snap fit with each other and are all Mini compatible
All the doors are locking ensuring the contents don't fly out when being moved.
The Print-In-Place feet allow for easy rotation of the stack, and the locks ensure the motion doesnt throw open the drawers
Lastly, each drawer has an easily removeable contents label slot to allow you to OCD your storage as much as you want.

Unfortunately, i couldnt get away without any hardware, and a threaded rod and some nuts are still required for stability... maybe next version :)

UPDATE 28/02/23: Added a square base frame option (Base2)

UPDATE 30/10/21: Added the sketchup file for anyone to tinker with.

UPDATE 27/01/21: Updated the locking peg model to be easier to grip and changed the size slightly to allow for worse tolerances.

UPDATE 27/01/21: Added a new set of files for the Small Parts inlay trays, designed to make getting the tiny little parts out of the trays easier, and subdividing the space further.

Additional parts required:
M6 threaded rod
2x M6 nuts
Amazonbasics spools

Construction Instructions:
Image 1: Base parts and spindle
Image 2: Layer Parts
Image 3: Top Parts

Instruction images:

1. gather the base parts, thread the base plug onto the thread and screw on a nut to the end, pushing the base plug onto the nut (i used a locktight threaded nut for this part).
2. layout the quart parts
3. clip in a centerplug to keep them together
4. thread the spindle through this assembly, this may require you put it together in a different method depending on how tight the center plug holds things together.
5. find the feet
6. clip the feet to the base assemble
7. grab a spool and thread it over the center plug on your base assembly
8. grab your drawer set of parts
9. slot in the dividers and the locking pegs with the flag facing out
10. Identfy the lower draw
11. Identify the upper draw
12. push the upper draw onto the spindle of the lower draw part - if these are quite tight you may need to lightly deburr the upper part to fit, and slot them together with a rotating force
13. slot the drawer assemble onto one of the base assembly corner hinge points
14. slot the drawer assemble closed, the lowest locking peg should slot into the base, locking it in place
15. repeat for your whole base layer of drawers
16. assemble the parts for the second layer using the existing assembly as a base
17. lock a center plug onto this layer assembly
18. slot on the second spool, repeat steps 8 to 17 for the number of spools you're using
19. to complete the spool storage the top parts need to be assembled, gather 4 quarts and a center plug, lock the center plug on the underside of the quart assembly
20. slot it over the main spool tower
21. slot over the top base brace
22. slot over the second brace and lock into the towers corner sockets
23. drop on the handle and thread a nut onto the remaining spindle, tightening it all down.
24. locate your labels and slot them into the drawer label slots

Tip: if you dont need to use the divider, slot them in the back of the tray behind the tray name text on the inside.

Tip: If you print the full center model instead of quarts you can skip multiple stages of the build and it ends up more stable too.

Print instructions

The trays were printed in PLA, the connectors and dividers were all printed in PETG.

All prints are orientated correctly to print without supports for the most part.

One item require supports:

Base-Foot - requires support enforcers for the print in place wheel and connector, a 3mf is supplied with the required support enforcers.

!! The G-code is specific for my mini configuration so it is set to have a higher temp and slower infill speeds, adjust for your printers tolerances and materials !!