I previously uploaded OpenSCAD files for making a do-it-yourself air wound coil (inductor) using a 3D printed form with a taper to allow the finished coil to easily slide off the form. That's still probably the simplest and most effective way to make such a coil, but I wanted to see if I could come up with a design that resulted in a coil of uniform diameter. This is the result. The coil form itself is comprised of the central core and the four pieces shown in the first picture, and four of the strips shown in the second picture should be printed to actually hold the wire windings.
The OpenSCAD files are parametric. The number of turns, turns-per-inch, and size of wire are defined by statements in the file for the strips. The diameter of the coil is defined by the file for the form, and you should use that same value for the strips because along with the turns-per-inch sets the proper angle for the slots in the strips. The length of the coil form is separately defined, but should be just a little bit longer than the strips.
I left the strip as a separate file because only one printed form is required to make multiple copies of the coil, whereas four for the strips are needed for each coil. It should be easy to replicate the strip as many times as desired in the slicer.
A YouTube video explaining the assembly process can be found here:
The author marked this model as their own original creation.