I used to operate auto rewinder spool holders like https://www.printables.com/model/199248-narrow-double-stand-for-75mm-integrated-auto-rewin inside my dry-box. The challenge with those was that it always was kind of some fiddling with the axle and the integrated rewinder when changing spools.

As such I was enlightened when I saw the idea of https://www.printables.com/model/292276-auto-rewind-spool-holder-for-reprack, just that I didn't want mine hanging on a rack but simply standing in my dry box. As such I concluded that I could reuse the cylinder shells and the inner coils from there but just design my own standing frame for the same.

And this is the result: A set of frame modules that can be attached to each other with M3x16 screws and corresponding hexagonal nuts, each capable of holding two cylinders from the original model.

During the process, I had to resolve two issues I experienced with the original cylinder shells and inner coils when printed with PETG though:

1. The surface of the cylinders was too slippery for my spools, such that they were not capable of building up enough tension. I resolved this by adding some slices of electrical insulation tape on both sides of the cylinders, which has a nice side effect that this adds a great design touch to them.
2. The inner coils had too much tolerance inside the cylinders, which caused them to disconnect the inner connectors under tension and spontaneously free all collected tension energy in one shot, making the rewind mechanism non-functional. I resolved this by gluing the coils together at the inner connectors. The outer connectors did not show this problem so far such that cluing was not necessary keeping the window open for easy maintenance.

If you like to have the same auto-rewind spool holder you should start to print and assemble the cylinder shells and inner coils from https://www.printables.com/model/292276-auto-rewind-spool-holder-for-reprack, following the instructions there. You do not need to print the provided axle since my frame has one integrated.

After that, you may print as many modules as you need and screw them together after inserting the cylinders with the coils. When assembling mind the orientation of the cylinders!

I printed everything on PETG with a 0.4mm nozzle, 0.2mm layer height, no supports, and 20% infill. Besides the coils that for sure like the flexibility of PETG it probably doesn't matter so much which material you choose otherwise and the frame is designed in a way that it should print nicely with slicer standard settings.

For your convenience, I added my sliced gcode files. Note that the one for the cylinder shells prints 10 shells (for 5 spools) at once and also prints one axle that is not needed for the final assembly but I added that for testing the cylinders and coils before assembly.

The other parts I used to build the complete dry box for the Prusa MMU2S (or any other setup with 5 filament feeds) can be found in those links:

1. Dry Box PTFE Tube Passthrough https://www.printables.com/model/30039-dry-box-ptfe-tube-passthrough (5 times)
2. Silica gel mount at https://www.printables.com/model/207372-silica-gel-mount
3. optional: Universal Filament Filter and Lubricator at https://www.thingiverse.com/thing:492067 (5 times)