I found this thread via Boing Boing..
I started wondering how to do it with sliding leaves (as opposed to pivoting).. As such there'd never be a gap between the leaves. Same effect as having thin overlapping leaves.. Here the iris will completely shut.
I don't have shopbot... but I do have Google's SketchUp..
Since I don't have any way of actually building it, I didn't finish the design..
There'd be another rotating ring with slots or rods (as the "steampunk" version) that pushes/pulls the leaves in their tracks/rails. Also, the leaves could be tongue and grooved..
Thoughts?