Parametric Flexible Z Coupler

This is an OpenSCAD version of thing:5439. I really liked the original design, since it allows me to use the Parametric Prusa Lower Z Axis Mount (thing:19313) at the bottom of the z screws to support the weight of the x-axis without over-constraining the z-axis (as opposed to having the full weight of the z-screws and x-axis just hanging from the z-motor shafts in the standard Prusa design). However, I needed to modify it, since the shafts on the NEMA 17 stepper motors I got on Ebay were turned down to 4mm instead of the standard 5mm, and I am using 1/4"-20 threaded rod for my lead screws.

This file allows you to easily specify outer diameter, both shaft diameters, spring section length, end section length, center section length, number of twists per spring, number of sides on the coupler (facets), and the duty cycle of the spring (fraction of the spring that is solid).