Estimated time to complete: ~2 hours
- Card or heavy weight paper
- Drinking straw
- Xacto knife
- Glue stick
- Glue gun (or just make do with the glue stick)
- Small cross-head screwdriver
- Large cross-head screwdriver
- Rubber bands
- Aperture, 5-50 mm
- Outside diameter, 100 mm
- # of blades, 8
- Rotational movement, ~80 degrees
- Pin size, 6 mm
- Blade thickness, ~0.25 mm (0.01″)
Making the parts for the cardboard mechanical iris
To create the iris design template I used iris-calculator.com, which generates the plans to help you. If you’d like to make the exact same one as in this guide, here are the PDF template files for you to download and print:
Print the template directly onto the card, and cut around the profile of the blades.
The housing for the cardboard mechanical iris is created using 4 parts (2 of which are identical). You may need to use a few layers of cardboard depending on how thick it is.
1. Base and Lid
Insert the blades into the holes in the actuator ring. Carefully layer them all around so they stack neatly in the open position. The last few can be challenging – just fan them out a little to gain access to the holes.
2. Start gluing the body together
3. Mate the parts
4. Glue the wall on
5. Check everything
With the aperture closed, draw a picture, then watch it explode and re-assemble when you open and close the iris!
Notes on the cardboard mechanical iris
Hard to open/close
For a smoother operation, use a pencil to coat over all the moving surfaces – particularly the slot edges and outer edge of the actuator ring.
Aperture is not round.
It’s unlikely with a cardboard iris that the aperture will be perfect. You can try replacing blades, and double checking the slots and holes have been made properly.
Won’t open / Won’t close
This could be 2 things: The handle slot is in the wrong place, or the blades have been made the wrong way round.
The iris dosen’t close completely
By design, this iris closes down to a minimum aperture of 5 mm. If you’d like the iris aperture to close completely, take a look at our other article on Dual-Plane irises.