Iris Box

Material
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Out of a 4mm multiplex wood, laser-cut (see files) :
- bottom layer : screw head holes
- 2nd bottom layer : cavity bottom + screw threading holes
- cavity slices (here 6x)
- big ring gear
- 5x small inner gears
- 5x blades
- one more cavity slice to retain the hexagonal nuts
- hexagonal nuts holder slice
- top ring

Ironmongery:
- 5x screws : M4, 4x40mm
- 5x hexagonal screw nuts
- 5x large washers
- 5x small washers

Tools
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- wood glue
- flat screwdriver, medium size
- sand paper (120-180)
- some weight (heavy book), or clamps
- optional : cutter

Step 1: Top Rings

Assemble the top rings:
- Put glue dots on the hexagonal holder slice (image #1)
- Place it on the top slice
- Place the hexagonal nuts in their holders (image #2)
- Put glue dots on the hexagonal nuts retainers slice (one of the 7 cavity slices) (image #3)
- Place it on the hexagonal holder ring (image #4)
- !!! Make sure that the holes are aligned !!! Try to insert M4 screw into the holes to confirm that it is actually possible to screw into the nuts.
- While the glue is drying, press the assembly under some weight (heavy book or so), or use clamps (image #5).

TIP: if you use clamps, do not press to hard to avoid distortion.

TIP: make sure to keep all the slice aligned while pressing, and wipe off the glue that might drop off the assembly, otherwise it will look like a pile of pancake covered with maple syrup (image #6, mmmmmhhh, nom, nom,...) :-)

Step 2: Bottom and Cavity

Assemble the bottom layers and cavity slices.

A word about the number of cavity slices.
Their number depends on the wood you're using, and the length of the screws.
The screw threading must go through 5 slices + N cavity slices, and 2 washers:
- 2nd bottom slice : cavity bottom + screw threading holes
- Nx cavity slices
- washer, about 0.5mm thick
- the gears slice
- blades slice
- washer, about 0.5mm thick
- one more slice, similar to the cavity slice to retain the hexagonal nuts
- hexagonal nuts holder slice
This model is using 4mm multiplex wood, and 40mm screws (threading, head excluded).
Making the calculation gives us: (5+N).4mm+2.washer = 40mm --> N = (40-1)/4 - 5 =  4,75 --> 5 cavity slices
But the wood is actually a bit thinner than 4mm (3.6mm or so), so an additional 6th cavity slice is needed.
As a summary : make a test first; pile up the wood slices and compare with your screw length to determine the correct amount of cavity slices.

- Put some glue dots on the bottom slice (image #1)
- Place the 2nd bottom slice (cavity bottom) on it, so that the screw holes are aligned (image #2)
- While the glue is not dry yet, insert the 5 screws (image #3)
- On each cavity slices, put some glue dots (image #4), and stack them on the bottom slices (image #5)

Then, use a weight (need to remove the screws) or clamps to keep all together while the glue is drying.
You can also screw in the hexagonal nuts, but that will not keep the very bottom slice in place !

Step 3: Blades and Gears

Assemble the blade and the small gears.
!!! This part needs to be really cautious about the position of each gear relative to the blades.

For easiness, we will use the screws to align the blades and the gears.
- Place the first blade on one of the screws
- Put some glue on the blade, around the axis
- Place a small gear on the blade. Observe carefully the (rotational) position of the gear relative to the blade. ALL the other gears will have to be in the SAME position. For your convenience, you are free to choose which position you can reproduce more easily, but it is important that, in final, ALL the gears have the SAME position.

- Do the same for the other blades and gears
!!! Pay attention to place all the gears on the same side of the blade !!!
On image #1, I placed them in a row on the same screw, but you can use one screw per blade.

Let the glue dry.
Later, when we will place all the blades together on the box, we will see that some gear teeth will obstruct the assembly and the blade will not fit side by side. We will have to cut out some of the teeth.

When the glue is dry, remove the blade/gear from the screws and make sure they form a SOLID assembly.
Use a sharp cutter to cut the extra teeth of and/or use sand paper to sand them off. Do not be afraid; we do not need these bits.
See image #2 and #3.
The result should look like image #4 and #5.

Then, make sure the hole is clear.
To do that, use a screw as a thread and move it back and forth into the hole to scrap off any excess glue (image #6).
In result, the screw must move freely into the hole.

Step 4: Final Assembly

Image #1 shows what you should have achieved by now.

- Place the big washers on the screws/box
- Place the big ring gear on the box
- Place all the blades/gears, ALL in the same position
- Place the small washers
The result should look like image #2.

- Place the top ring assembly (image #3)
- Hold all the pieces in one hand and start to screw VERY carefully (image #4). Turn a bit each screws at a time to be sure not to force or distort the assembly.
- The screw MUST remain loose, the blades MUST move freely. Screws are used the keep the top ring in place, not to tighten something. When you shake the box, you should hear the blades and washers move.

Make some opening/closing trial, adjust the screws, make more trials...
When you a satisfied with the screw position, you can put some glue dots on their head to maintain them in place (image #5).

Done !

Step 5: Finished

Here are photos of the final object and opening sequence.

You can also have look at a short video of another box here (a bit wider, and not completely finished).
This other box can be generated from the parametric OpenSCAD file provided in this post.