The “Filament Spool Rack” from ihateu3 (thing number 5865345) was exactly what I wanted, but it was made for inch sizes and since I live in Europe, I had to adjust it to millimeter sizes for the rods that go through the rack. In the meantime, I have become the proud owner of a Creality K2 with a build plate of 350x350, so I could also print the parts in 1 piece. I had also started to delve into Freecad and all this seemed like a nice practice path. That led to me redrawing the entire rack in Freecad in mm sizes for a 12 mm steel tube (outside) that could be purchased cheaply at the local hardware store (Hornbach).

Parts: A.stl can hold two rows of spools. Of course, you have to print at least two to hold the rods in between. My advice would be to keep a maximum distance of 1 meter between the posts, preferably a bit less (I keep to 75 cm because my rod is 1.5 meters long)

B.stl is a riser. If you were to put two A parts on top of each other, you would not be able to use the second row of rods, the third row is in the way. To prevent that, there is the B part, with which the distance is adjusted and all four rows can be used.

C.stl is there if the combination A, B and again A becomes too high for the available space. In that case you can use the C.stl and place it on the A.stl, this then gives you access to three rows of coils.

A-End.stl is the same as an A.stl, except that the top two connection holes have been omitted because this is an end piece.

C-End.stl is the same as a C.stl, except that the top two connection holes have been omitted because this is an end piece.

Feet.stl is an extra wide foot (diameter 75mm) that you can mount under the uprights to prevent any wobbling of the uprights. Pin.stl is the connection pin between the uprights.

Because this depends on the adjustment and accuracy of the printer, my advice would be to first print an A.stl, B.stl or a C.stl and then a Pin.stl. Check whether the pin fits in the connection holes and adjust a small enlargement or reduction percentage if necessary. The tighter they fit, the better the end result. The connection holes themselves are 11mm deep per side (so 22mm space for a 20mm long pin) more than sufficient for the pins.

Disclaimer: I only printed the A.stl and the C-End.stl with the Pin.stl because I didn't need more for the available space I had. I HAVE NOT PRINTED OR TESTED ANY OTHER PARTS. However, I see no reason why this one would not work, but if something is not right, I would like to hear about it and adjust it if necessary.