Here is the sample of iris (diaphragm) mechanism (diameter 64mm, thickness 12mm) I made with LibreCAD - the best soft for movement calculations.

Simplest design, very easy to print, no glue, no nuts, no screws!

To achieve the result you need to print:

• top, middle, bottom - one time
• leaf - six times

It's recommended to use filament of different colors for different parts.

PETG, ABS, PLA and any other (besides Fex and Rubber) - good choice for the thing filament

Creality, TEVO, Prusa, Anycubic, Anet, Flying Bear, Wanhao, Reprap, Ultimaker - 100% printable with good result.

I use Ender 3 (with standard hotend 0.4) and about 1 hour to print this design.

!You have to trim the edges if middle part since it connects rigidly and tightly!

You can use a thinner nozzle and layer height to archive maximum accuracy

May be you need sandpaper or nailfile to smooth edges.

You can also try antistress toys I made:

https://www.thingiverse.com/thing:4855514 https://www.thingiverse.com/thing:4859177 https://www.thingiverse.com/thing:4858354 https://www.thingiverse.com/thing:4857857 https://www.thingiverse.com/thing:4854632