Hello, and welcome to my guide on creating your own light-up elemental arrows! This past Halloween, my son decided to be a ranger from Dungeons and Dragons, and no self-respecting ranger would venture out without magic arrows to help defeat monsters. We started talking about how we could create some special arrows, and I thought of some random LEDs we had in the house. An idea began to form - we could create our own elemental arrows! The goal of this project was to make something my son and I could design together, then print and assemble quickly and inexpensively. We were extremely excited about how the arrows turned out, and I wanted to share our process!

Supplies

The supply list for this project is intentionally simple:

Materials:

Assorted 5 mm LEDs
CR2032 batteries
1/4" dowel rods
Translucent printer filament, like this one by 3D Solutech
Super glue, I used Loctite Ultra Gel Control

Tools:

3D printer
Wire snips
Hand saw
Sandpaper

Optional:

Alcohol ink, either homemade or purchased

Step 1: Modeling the Battery Holder

The first step I had to figure out was how to power the LED and hold things inside the arrow. I decided to use CR2032 batteries for this project. While this type of battery is larger, they are cheap - I paid $0.25 each - and can power an LED directly. After looking at some different ideas for holding these batteries and LEDs, I decided to jump into Fusion 360 to design my own.

I used a pair of dial calipers to get the battery measurements, then started with the rounded base of the holder. I then extruded the main body of the battery holder, cut out the opening for the battery, made the inset on top for the LED, put holes in the sides for the wires, and added the hole for the dowel rod on the bottom. I made the battery slot slightly larger than the thickness of the battery to allow everything to be held together with a pressure fit. You can download the battery holder below or from Thingiverse.

If you model your own holder, be prepared to try multiple prototypes. My initial design, version 1 in the photos, was far too large and took over two hours to print one. Based on my test print, I reduced a lot of the dimensions to create version 2, which printed in about 30 minutes. However, as I tested that design, I found that I had taken too much material out - the design didn't print well and didn't hold the dowel rod well. My final design, version 3, struck a balance that I was happy with. That rapid prototyping is a huge advantage of using your own designs in a program like Fusion 360 - I managed to model and print all three major revisions, plus a few minor tweaks, over the course of one day!

Battery Holder.stl
Download View in 3D

Step 2: Modeling the Arrow Tips and Fletchings

Once the battery holder was ready, it was time to get creative! We had red, blue, green, yellow, and white LEDs on hand, so we settled on fire, lightning, poison, and water. I decided to create the arrows in halves, so I could easily print two copies, then glue them together. Since the battery holder had to fit inside every part, I started by creating a basic template that would define the smallest I could make the interior of the arrow. You can grab my template for Fusion 360 at this link: Arrow Base Template

The next step was to create the arrow tips and fletchings. For each arrow, my son and I sketched out the basic shape we wanted on paper, took a picture of the sketch, inserted that sketch into Fusion 360, and scaled it to the right size. From there, I showed him how to use the spline tool to trace the drawing, making sure to project the edges of the template and connect the splines at the end points. We extruded out the shape, then used the shell tool to hollow out each part. When shelling, we removed one of the main faces of the arrow as we were going to print two copies and glue them together. Also, we needed to have a flat edge to insert the battery holder, so if the design had a curved end, like the fire arrow does, we had do this process in two stages to keep the edge of the template and remove the curved edge of the arrow.

After shelling the design, we created the cutouts to insert the battery holder. For our design, that required two extrusions - a rectangle all the way through the edge for the upper part of the battery holder, and a rounded extrusion to a depth of 1/16" for the based of the battery holder.

The arrow designs we created can be downloaded here or on Thingiverse.

Step 3: 3D Printing the Parts

With the battery holder, tip and fletching files ready to go, it was time to print the parts I needed. To let the LEDs shine through, I purchased some Sunlu translucent PLA+ filament from Amazon. That filament is not longer available, and honestly I had a few issues printing with it, but there are a lot of other translucent or clear filaments you can purchase. My printer is a Printrbot Simple Metal with a 0.4 mm nozzle, and each part was printed with 3 walls and no infill. For each arrow, you need two battery holders, two copies of the tip, and two copies of the fletching. All told, it was about 4 hours of printing per arrow. The only exception to printing two copies is the fire arrow. Because that design is not symmetric, you need to print one regular part and one mirrored part. Your slicer program should be able to mirror the .stl for you.

If you don't have a 3D printer, you can check to see with your local library, which may have a 3D printer you can use, or you can use a service like 3Dhubs.com or printathing.com to print and ship the parts. I've never used either service myself, so I can't address the service or the quality of the prints.

Step 4: Assembling the LEDs

All of the parts are ready, so it is time for assembly! Start by assembling the battery holder. You'll need one holder, one LED, and one battery.

Bend the legs of the LED out flat out to each side up against the LED itself, set the LED on top of the holder, then bend the legs back down so the LED sits on top of the holder.
Using the wire snips, cut the wires of the LED so they are about a quarter of an inch below the small holes of the battery holder.
Next, gently grab each wire of the LED just above the hole and, without cutting the wire, bend it inward to insert the wire into the hole on each side of the holder.
You will see the two wires poking out inside the holder, so use the wire snips or another flat object to bend each wire flat against the inside of the holder. This bend should hold the LED tightly in place on the battery holder.
Finally, insert the battery! If the LED doesn't light up, try flipping the battery over and reinsert it so it lines up with the positive and negative legs of the LED.

Note that due to the tight fit of the wires and the battery inside the holder, you may have to push the battery out from the slot on the back of the holder. Use something dull, like a bamboo skewer or a pen, to avoid damaging the battery when you remove it.

Step 5: Assembling the Arrows

It is finally time to assemble the arrows! Cut the 1/4" dowel down to a length of about 15" (or whatever length you prefer) for each arrow shaft and sanded the ends down just a bit to get a better fit on the battery holders. Next, use the super glue to glue the two halves of each tip and fletching together, then glue a battery holder on to each end of the dowel rod. Make sure to set the dowel rod and battery holders on a flat surface to line them up properly. I failed to check the alignment and almost assembled one arrow with the tip and fletching rotated 90 degrees from each other.

My original plan was to use a pressure fit to hold the arrow tips and fletchings on the shaft so I could quickly remove and replace the batteries, but a few of the ends kept popping off. In the end, I found that a small dot of super glue on each end of the battery holder was enough to keep everything in place while still letting the arrows be disassembled easily.

Step 6: Adding Finishing Touches

The arrows looked great assembled and lit up, but we decided a bit more color for using the arrows in daylight. We applied a coat of alcohol ink to the outside each arrow give it a rich color, though this step is entirely optional. You want to use a transparent paint, like these alcohol inks on Amazon, or you can try making your own. Of course, if you have other colors of transparent filaments, you could bypass this step entirely!

Step 7: Taking It Further!

Overall, my son and I were extremely happy with how the arrows came out. They looked great with his costume, and his friends were very jealous! That said, if I were to redo this project, I would make some changes. We designed the arrow parts with flat sides to make them easier to model and print, but I would love to redo these in a more dynamic, 3D style. Also, while the LEDs diffused well through the plastic, a more spherical style would move the LED further away from the outside and help it diffuse more evenly. I would also be interested in trying to frost the inside of the arrows to improve the diffusion. We also ran out of time do anything with the arrow shafts, but I think some color or stain would have made them look even better. Finally, I think there are a lot more elemental arrows you could create using this idea! If we had had a bit more time, we were going to use a white LED to create an ice arrow, but we also sketched ideas for dark, light, and exploding arrows!

Thanks for reading my Instructable, and if you create your own elemental arrows, I would love to see them!