Mechanical Iris Box

This instructable will show you how to make a box lidded with a mechanical iris. I originally made the mechanical iris as a prototype for a different project, but the prototype ended up working nicely and I didn't want to waste it. I had an old clear plastic container that was taking up space in my kitchen pantry, so I decided to recycle it and make a cool box!

I designed the mechanism so that I can be assembled with only acrylic pieces. So, the iris is not held together with any metal nuts or bolts; rather, it is held together with acrylic pins made from small acrylic circles stacked on top of each other.

The iris mechanism has 5 leaves, so the leaves don't overlap at all. One thing that I see in most 5-leaf iris designs is that the outer ring is very thick, making the iris opening very small compared to the size of the entire mechanism. I wanted to minimize the ring width and maximize the iris opening as much as possible. Fortunately, I found this design off of Thingiverse that has the desired qualities. I modified the file a little bit in Adobe Illustrator so that it would fit pins made out of acrylic.

Let's get started!

1/8 inch thick acrylic

Laser cutter

Round plastic container with opening diameter between 3 and 4.8 inches

Acrylic cement and syringe applicator

Hot glue

I've included an Adobe Illustrator AI vector file and a PDF file that you can use with your laser cutter.

The red lines indicate that they should be cut through the wood, and the blue lines indicate that they should be etched onto the surface the wood, but not cut all the way through. The etchings will guide us when we are glueing the pieces together in a later step.

There are several components to the mechanism: the bottom ring (which is the ring with 10 circular holes in it), the 5 leaves, and the top ring, which is the ring with C-shaped holes and spikes at the edges. There are also 0.25" diameter circles and 0.4" diameter circles, which we will use to form pins to hold the mechanism together.

There is one component that I didn't include in the design file, that you might want to add to your file. I also cut out an additional circle that I glued to the bottom of the inside my plastic container. I did this since it's a clear recycled container and I wanted to hide the unnecessary text on the bottom. I didn't include this in the file since different containers have very different bottom diameters. So, if you want a circle on the bottom of your container as well, you should measure the inside diameter of the bottom of your box and add an additional circle with that diameter in your laser cutter file.

I used a Universal Systems laser cutter to laser cut the design out of the 1/8" acrylic.

Make sure to set up the design file to work accordingly with your laser cutter. In the design file I've provided, the red lines indicate that they should be cut through the wood, and the blue lines indicate that they should be etched onto the surface the wood, but not cut all the way through. Adjust the line widths and line colors in the design to work with your laser cutter, so that the lines are correctly etched or cut. After laser cutting the file, you should have two piles of small acrylic circles: one pile should have circles with a diameter of 0.25 inches, and the other with a diameter of 0.4 inches. Put these in a container so they don't roll around and get lost.

Since we aren't using any bolts to hold the mechanism together, we will hold everything together by making pins with small acrylic circles attached together with acrylic cement. You should have 2 piles of small acrylic circles: one pile should have circles with a diameter of 0.25 inches, and the other with a diameter of 0.4 inches. The other larger acrylic pieces should have an overall total of 15 circles etched onto their surfaces, on which you will glue an acrylic circle. In each of the 5 leaves, there should be a circle etched close to the middle of the leaf, and the bottom ring should have 10 etched circles. These etchings will act as guides to indicate where we should place the pins.

Make sure you are working in a well ventilated area so that you don't breathe in too much of the toxic fumes from the acrylic cement. Also make sure you are only using a work surface that is compatible with acrylic cement, like wood, metal, or concrete. Do not work on a surface of paper or glass when you are glueing things together with acrylic cement.

This step takes some precision and a steady hand. Take one of the leaves and locate the etched circle towards the middle of the leaf. Dab a small dot of acrylic cement in the middle of the etching, and place one acrylic circle on top. Be sure that the edges of the acrylic circle line up precisely with the edges of the etching. Repeat this for the other four leaves. Set the leaves aside so they can safely dry and harden without being disturbed. Now you should have five iris leaves, each with an acrylic circle glued on the surface.

Now it's time to glue acrylic circles to the bottom ring. The bottom ring should have 5 pairs of circles etched onto its surface, for a total of 10 circular etchings. The 5 holes that are closer to the inside of the ring should have 1 acrylic circle glued on top. The 5 holes that are closer to the outside of the ring should have 2 acrylic circles stacked on top. So, when you are done with glueing acrylic circles to the bottom ring, it should have a total of 15 acrylic circles glued on tip.

Make sure when you are glueing the acrylic circles, you are being very precise in positioning them within the edges of the etching guide. Also make sure to line up the edges when stacking 2 acrylic circles together. This ensures that the iris mechanism will work smoothly.

Now that you have the pins glued, it's time to put the whole mechanism together.

First put the bottom ring (the one with acrylic circles glued on top of circular etchings) flat on your work surface, with the pins facing upwards. Then place the 5 leaves on the pins by placing the hole in each leaf on one of the pins of the bottom ring (the pins that are closer to the inside of the ring). Then, carefully position the top ring (the ring with oblong holes) on top, so that the pins from the bottom ring comfortably rest between the holes in the top ring. You might have to fidget with it a little bit to get the position right.

Now we need to top off 5 of the pins connected to the bottom ring to prevent all of the pieces from coming apart. Take out your hot glue gun and plug it in. Once the glue gun is hot enough, dab a small blob of hot glue on one of the pins closer to the outside of the ring, and then stick one of the 0.4" diameter acrylic circles on top. Repeat this for the 4 other pins.

Now we will attach the mechanical iris to our box.

If you want to add an acrylic piece to cover the bottom of your box, apply a circle of hot glue to the acrylic piece and press it on the bottom of your container until the glue has hardened. Then, apply a circle of hot glue around the rim of the container and press the mechanical iris onto the top of the box until the glue hardens.

Viola! You're done!