UPDATE Iris ~120mm for Stepper

Update nov 2025:
The spacers were a bit too short, which may have caused the lamellas to be slightly too squashed. I apologize for that. The new spacers should work better. Ideally, secure them with self-locking nuts and perhaps don't overtighten them. If the lamellas still aren't moving completely smoothly, try using some silicone spray.

Iris / shutter / Blende / Aperture based on https://www.thingiverse.com/thing:773759
In one of the pictures you can see the size comparison
I scaled and changed the design to fit a 28BYJ-48 Stepper.
The size was determined by the prusa mini printbed dimensionen.

you have to print 11 lamellas/leaves and pins

you may have to turn and rotate the parts so that they can be printed on your printer

a few of the spacers (I used nuts instead)
some M3 and M4 screws to put it all together.

I used silicone spray to improve the mechanics
the opening of the iris is between ~ 15-117mm.
It can not close completely

last image:
OPTIONAL: depending on your way to control the stepper you may need some kind of emergency stop. I cut a few teeth so that the motor cannot go beyond this point

Happy printing!