I thought it would be fun to turn spent 3D printing filament spools into the core of a storage system, and my CadQuery script for generating individual elements can generat a base module matching a removable storage tray using the same parameters. There are two categories of dynamic configuration involved: that to match the spent spool, and that to match user need.

To match a particular spool, the variables I expect to see are the inner radius of the spent spool, the outer radius, and the thickness of a spool. (Which dictates the height of a storage tray.) These are the variables I saw when trying it on two different types of one kilogram spools. (MatterHackers Build, and Filament PM.) I suspect there are additional variables that I have not yet encountered, and they will require future revision. I'm also curious to see if this design will scale well both above and below the popular single kilogram size. Some of the more expensive materials are sold in spools less than one kilogram, and filament can be bought in bulk on large spools 2kg, 3kg, and maybe more. I await a chance to try those in the future, or get feedback from someone else who has tried.

To match a user need, the size of the tray can be varied in terms of angles of degrees of the pie wedge. The low end is constrained by the size of the handle, which is fixed size regardless of the size of the tray because it is meant to fit human fingers and finger size doesn't change as the tray size changes. For one kilogram spools of 20cm outside diameter, the practical lower limit is a 15 degree wedge. On the high end, I suppose the geometric limitation is 180 degrees because anything larger would start to wrap around the center of the spool making the tray difficult to remove. As a practical matter, though, 120 degrees appear to be the limit and even then we'd probably want a tray with thicker sizes instead of single-wall vase mode. My test prints of 120 degree wedges in vase mode were unacceptably flimsy, though this may be a matter of filament selection.

While testing various sized wedges, I was amused by a happy coincidence. For testing purposes I printed trays of various angles in degrees: 15, 30, 45, 60, 90, and 120. When I put them all together, I discovered that list add up to a full circle 360 degrees filling up a spool. Convenient! Another happy coincidence with my design is the need for a little bit of clearance below the retention ring also gave me a nice label area for my tray.

Source code for this project is publicly available at https://github.com/Roger-random/r2s4