Laser-Cut Infinity Dodecahedron (Fusion 360)

I have been wanting to build my own infinity dodecahedron for years. The depth seen in these beautiful objects never fails to amaze me. However, after building an infinity cube a few years ago, I decided that I needed access to a laser cutter before attempting the dodecahedron. Fortunately, I recently gained access to one at my university's makerspace and immediately began designing and building it!

I ended up with this model! It contains 270 LEDs and is relatively small compared to other infinity dodecahedrons, with a distance between opposing pannels of only 18 cm.

To ensure that anyone could recreate the entire process of designing and building this project, I divided this instructable into four parts:

• Designing in Fusion 360
• Laser cutting the frame (including exporting for laser cutting in Fusion 360)
• Building
• Programming

I hope you will have as much fun as I did building this and end up with a great-looking project!

Note

Having a laser cutter available for this project is a must. I used this project to increase my experience with laser cutting, and thus it heavily relies on its use. But don't worry, if you do not have a laser cutter available to you, this 3D printable infinity cube might be for you!

You will need steady hands for making this project, since the soldering needs to be done at "sub-optimal" angles. Let's just call it a good practice/ a fun challenge.

Electronics

• 2 meters of 144 LEDs/meter ws2812b strip (aliexpress)
• A few meters of thin gauge wire (preferably red black and green)
• A microcontroller (I used an Arduino nano every since I had one laying around)
• A few meter of usb A cable
• 5V 5A power supply (a phone charger with less amps also works if you run LEDs less bright)
• Some dip LED diodes (only the legs of them are being used, sorry LEDs)

Materials

• 3mm plywood
• 3mm Acrylic
• One-way mirror film

Tools and consumables

• Laser cutter!
• Wire cutters
• Wire strippers
• Scissors
• Soldering iron
• Solder
• Glass cleaning spray
• Squegee (for applying film)
• Some tape

As I was thinking of ways to build platonic solids from laser-cut material, I settled on the designs shown above. Instead of connecting the outer panels to each other via tabs on the sides, this design connects the outer panels together via connectors on the inside. The pieces on the inside also serve as a great place to attach the LED strips. The icosahedron above was the first test piece I made, and since I liked the way it looked, I went on to design a dodecahedron. No glue is used in these builds; all pieces are just pressed together. This approach is also used in the final build and is surprisingly sturdy. All that is left to do is to design one that has the correct dimensions to fit some LED strips!

From this point on, the parts of the dodecahedron will be referenced as follows:

• Outer panel: one of the wooden pentagons that forms the outside of the dodecahedron.
• Inner strip: one of the wooden strips that is on the inside of the dodecahedron. These pieces hold the LED strips.
• Connector: one of the pieces that connects the outer panels with the inner panels.
• Mirror panel: one of the panels with a one-way mirror.

There will be three different versions of the outer panel: a normal one, one with a cutout in one corner so a cable can fit through, and a top piece that has a weaker friction fit so that it can be removed later.

In this step I will go over the design processes for this project. If you are interested in this, I advise you to download the attached Fusion 360 File. This way you can follow the process easier, or even better, move around in the timeline yourself to see everything step by step! Downloading the file also allows makes it easier to make your own modifications or customizations.

Alternatively, if you select the model browser in the frame below, you can use it to display different components of the design, to get an idea about how it all fits together.

Designing a scalable Dodecahedron

I used this video to design the base dodecahedron. This video builds the dodecahedron by placing multiple patched together. These patches are copied and rotated by their dihedral angle to build the solid. Keep in mind that it is important to use a parameter to constrain the dimensions of the base pentagon, so that it can be resized later.

Add the necessary construction elements, such that the center of the dodecahedron can be marked with a point.

Once completed, it might be nice to move this body into its own component, since it will only be used for reference later on.

Note

This approach of designing a dodecahedron is preferred over using a 3d sketch, since fusion 360 might have difficulties with solving 3d sketches when resizing.

Designing the inner strips

The inner strips are the sections that will hold the LED strips. The dimensions of these pieces are based around the LED strips. Since the two meters of LED strip has a total of 288 LEDs, and a dodecahedron has 30 sides, 288/30 = 9.6. Because you can't use half LEDs, 9 LEDs will be used per section, which thus need to be 70mm long. The sections wil be 13mm wide to accommodate the 12mm wide strip.

This strip wil be intersected with a section of the dodecahedron, that is one thirtieth the total volume. These steps just provide the outer contour. The holes will be made later.

Designing the outer panels

The outer panels will form the outside of the dodecahedron, the mirror panels will also be glued to these pieces. Now that the inner strips are designed, we can offset the projection of these parts by a few mm, to allow for space to put the mirrors on. The outer edge of these panels is just one of the sides of the base dodecahedron extruded.

Designing the connectors

Once those two parts are designed, it becomes easier to design the connectors. Open a sketch perpendicular to the previously designed components, and project the intersection of those parts. Design the tabs and some space for the cable, and you're good to go.

All wooden pieces of this build are press fit together, thus, it is important that all parts fit snugly together. Therefore you will need to adjust all parts for the kerf of your laser cutter. For my laser cutter the kerf was 0.25mm, so all parts were offset by 0.125mm. If you do not do this, all parts still fit together, but they will need glue. I advise you to cut out a few of the necessarry parts first to make sure they fit together snugly.

You will need to laser cut the following wooden parts out of 3mm plywood

• connector.dxf * 150
• inner_strip.dxf * 30
• outer_panel_top * 1
• outer_panel_cable_hole * 3
• outer_panel_normal * 8

Alternatively you can export the dxf files directly from the Fusion 360 model. You can easily export the bodies for laser cutting and adjust for your own kerf using this add-in. I really recommend this add-in if you laser cut objects regulary!

The following should be cut from acrylic with one-way mirror film already applied to it. This video contains instructions on how to go about applying it. Applying the film before cutting makes the edges look a lot cleaner.

• mirror_panel.dxf * 12

I first cut out larger pentagons and applied mirror film to each one individually. Then I went and cut the proper size pentagon out of each piece. This way I tried to limit inconsistencies in the mirror film, as it is easier to apply it to a smaller piece of acrylic.

Make sure to clean these pieces with warm water and soap before gluing them in place later on. This ensures they have clean reflections.

It becomes a lot easier to troubleshoot incorrect connections when you have an Arduino that is displaying something on the LEDs. Personally I always use this piece of demo code from fast LED. Just change the LED pin to the pin you use. Set the amount of LEDs to 270 and you are good to go. I use the Arduino IDE for programming.

Now you can start by soldering the first piece of LED strip. Grab a piece of old usb cable (something like 1 meter), and strip a section of the red green and black wires inside of it. Connect these to a section of 9 LEDs. Wire the other side of the cable to the Arduino.

You should now be able to see the first signs of life!

If you have trouble wiring them up correctly, please look at this instructable for some more information about doing so.

Once the first piece of the LED strip is connected to the Arduino, you can start building. Start by taking the two outer panels with a cable hole. Connect two together with 15 connectors and three inner strips. Make sure all cut-outs for the cable are in the same corner.

Now add the previously made section of LED strip. Put the cable through the hole, and put the piece of LED stip in place. You can put some glue around the cable to provide a little tension relief.

Now finish this section by putting the final outer panel with cable hole in place.

Now that the first three edge pieces are in place, the others can be added. The sketch shows the advised order of the LED strip sections. The red lines indicate strip sections, the blue lines show data cables that run behind other sections, and the green dot shows the starting point.

Slowly work your way around the bottom pentagon until you have all five surrounding pentagons in place. Now work your way around again until you have the other five in place. Wire up the final five sections of LED strip, and you're good! Make sure to test all LED connections regularly.

Be aware that the diagram above only shows the data connections of the LED strip. The power connections should always have a short path to the entry point of the cable. This is why you will see multiple cables connected to one end of the strip.

Instead of using cables for the really short sections, I used the legs of LEDs. Just hold them in place with tweezers while you solder them in place.

The second image shows how the data cables should be routed behind the back. Make sure not to close off any sections that still need these cables, as you cannot access them anymore once closed off.

Soldering these LEDs becomes more challenging the further you go. Make good use of those tweezers to keep everything in place. Tinning everything that you plan on soldering in advance is also definitely a must.

Once you have all the LEDs working, you can start gluing the panels in place. Make sure they are clean before gluing them in place!

First, remove the top panel of the dodecahedron. You will need to use this hole to enter the acrylic mirror pieces.

Then, remove the protective film from the back side of the acrylic. Place a drop of glue in each corner of the pentagon (on the side without the mirror film), and put the mirror into place and press it slightly. Wait for the glue to dry, rotate the dodecahedron such that another side that does not yet have a panel is facing the bottom, and repeat.

As for the top panel, just glue a piece of mirror in the center of it, whilst it is not attached to the dodecahedron. make sure the mirror is attached firmly and centered properly. Put this piece in place as the last piece, since it is hard to get it out again.

Note

It might be a good idea to check beforehand if the glue you use stains the acrylic and how well it bonds acrylic to wood.

The programming is currently quite simple. Unfortunately I haven't gotten to program any fancy code yet that utilizes the layout of the dodecahedron, but I will do this soon!

For the time being, I just stuck to the demo reel code from above.

If everything worked out, you should have ended up with a nice looking project. Let me know if you have any questions. Check out my profile for more LED projects.