First World Problem #473: Empty Filament Spools
Turn you empty spools into giant spinning tops! These easy-to-print inserts are sized for the 53.5mm dia holes in eSun/Inland spools, but you can re-scale them anywhere from 75% to 125% to fit your particular spool.
I've posted 3 different style tops. The spiral give an interesting visual effect when it spins, but it provides the least gription when you go to spin it up.
Watch them go: https://youtu.be/Cjf1cexgRSk
These are sized for 53.5mm dia holes. Accurately measure the diameter of the holes in your spool and scale up or down accordingly. In your slicer, you should be able to scale in just X and Y, leaving the Z scale at 100%. I'd suggest printing just the first few millimeters of the spool top tip to check the fit before printing the whole thing. (If you don't get a really tight fit, you can always use a few drops of superglue to hold the inserts in place.)
Make sure to print this pretty hot and slow. The walls are thing for quick printing but they should plenty sturdy if your layers are fully fused.
Getting your tops spun up takes a little finesse. Spin the stem between your sliding palms as shown in the video. The trick is to contact and release the stem with both palms at exactly the same time. Once you've got the top spinning, you can continue to recharge it with your palms as it slows down.