I wanted a nice way to use old, empty filament spools, so I decided to make a clock design based on them. All printed parts combined only use up about 80 grams of filament.

I added a openscad file for customizing all parts to fit most types of spools. 

How to make:

For mounting the diffusor to the spool I designed brackets with spacers which make sure that the distance between the spool core and the diffusor stays the same all the way around. I attached an image to show how to assemble the diffusion panel. The diffusor might look and feel a bit fragile when you first glue it in place. To fix that there's little brackets which are glued in place to cover the seams and to stabilize the thin panels.

To light up the diffusor you will need an led strip of some sort. I would recommend using a battery powered strip to get rid of the cable hanging down from the clock. There should be more than enough space to hide a battery compartment in the middle portion of a filament spool.

You will also need a clockwork. The holding bracket is designed to fit clockworks with a maximum size of 58x58mm, which should be able to house most standard clockworks. I recommend to glue it down into the bracket using a few drops of hot glue.

The bracket holding the clockwork in place should be a tight fit to your spool, since it is held in place only by friction. It cannot be glued in place, because you need to take it out to change the battery on the clockwork. You might need to break away a bit of the plastic of the spool in order to get the bracket in.

The Clock is designed for spools made by german manufacturer Janbex and i don't really know if they use some sort of standard size. I attached two images showing the measurements of my spools. If your spools have different measurements, it should be pretty easy to get the parts to match your spool in openSCAD.

Parts List:

1x Diffusor.stl
8x Diffusor_Bracket.stl
7x Diffusor_Seam.stl
1x Diffusor_Seam_With_Cable_Hole.stl
1x Clock_Face.stl
1x Clockwork_Bracket.stl

Note: If you use a battery powered LED strip, you can replace the Diffusor_Seam_With_Cable_Hole with a standard Diffusor_Seam.

Non Printed Parts:

1x Clock work (Standard Size, up to 58x58mm)
1x LED Strip

Mistakes I made so you don't have to:

There are two things I would have done differently now that I finished my clock. The first one would be to install a battery powered led strip to get rid of the ugly cable hanging down.

The second thing is to put the holes which were meant to hold the filament while the spool was not in use to the bottom or to close them down with a piece of filament and glue to prevent light leaking, which destroys the pure black and white look of the clock face a bit.

Other than that I am really pleased with how the design came out and I hope a few people will like it. If you print one of those clocks, feel free to post an image of it. I love seeing what other people do with my models.

Cheers :)