I wanted to print some cat toy springs for my Son's cats but what I found was too hard to print. I decided to try designing my own.

This STL makes two springs at a time with no supports needed - the wire has no overhangs greater than 45 degrees, and I use one spring to the support another as they print - no extra supports needed. Also, the top and bottom are sliced flat to start printing flat on the bed.

Print with a brim to keep it fixed to the bed, and use fine layer lines with the extruder fan on high to make separation easier. You might need a knife to start separating, but it satisfyingly zips apart once you get it going. My PETG was a little stringy, so I just ran a file inside before separating top clean it up on later prints.

I included a Freecad parametric model so you can change the diameter, length, and wire diameter in the Varset if you want different springs. I am a Freecad Nube (and Electrical Engineer - mechanically challenged), so please don't make fun of my poor attempt at a proper 3d model. Make sure you highlight both bodies when exporting the STL.