This filament shelf is designed to use two hollow aluminum pipes (outer diameter 20 mm, 1 mm wall thickness). The pipes slot into the holders.

The files include two holders (left and right) as well as an optional center piece for supporting longer pipes. I used 1 meter pipes and don't need the center support. Fully loaded with 14-15 spools, the pipes hold up well for me.

Variants:

short: Use only left and right mount (up to 1 m pipe)
long: Use left, right and center mount (>1 m pipe)
creative: Use multiple “center” mounts for solid pipes, longer versions, etc.

Printing

Print on its side, I would recommend at least three perimeters and 20 % infill. (Thats how I printed mine in PETG, they hold up well)

I recommend adding tree supports for the screw holes.

Mounting

I highly recommend using screws (diameter 4-6 mm) in combination with washers. This way, the mounting pressure is distributed on a larger area and I don't think that they will ever come off the wall.

The srew holes are 6.5 mm in diameter. The recesses for washers are 18.5 mm in diameter.

Mounting it is a two person job (maybe you can do it alone, but it will be finnicky)

1. Assemble the rack with both pipes (slot them in) to get the templates for your drilling holes.
2. Set the rack onto the wall and level it as a whole.
3. Mark the screw points on the wall.
4. Drill holes, insert dowels.
5. Screw one holder to the wall (use washers!).
6. Insert the aluminum pipes into the holder and slot on the other side holder.
7. Screw the second holder (use washers!).
8. Insert screw caps into the holes.
9. Done!

Mounting hardware I used:

screws: 5 x 50 mm (flat head)
washers: 6.4 x 18 x 1.6 mm
concrete dowels (bore 8 mm, 45 mm lenght)

You can adapt based on your needs.

Customization

I have attached the Fusion 360 files (parametric) for easy modification. Within reason you should be able to change the pipe dimension by just changing the parameters.