The scales are designed in TinkerCad. I made two versions: a heart shaped pattern and a mermaid scale pattern. I've also designed an enclosure that fits a Gemma M0, on/off switch and 350mAh battery (included with the mermaid scale design).

I've uploaded the finished versions to Thingiverse for easy download. Or, if you want to customize your own design, you can follow along with the video below.

Video Transcript

In this video I’ll show you how to design some heart shaped scales for 3D printing on mesh fabric, designed to fit Adafruit’s NeoPixel light strands inside.

We’ll use TinkerCad to design the scales. TinkerCad is a free online 3D design program that’s really easy to use. If this is your first time using TinkerCad, work through a couple beginner tutorials first to get a the hang of moving around the workspace.

Create a new design and give it a name. I called mine “heart armor”.

First we’ll model a rough shape our NeoPixel strand dot. I measured one of the dots with my calipers and added a little extra room for glue, and came up with some dimensions.

Drag a box hole into your workspace and make it 30 mm long and 9.6 mm wide. Make it 4 mm tall.

Scroll down in your shapes window and grab a half sphere. Make it 18mm deep and 15 mm wide, and set a height of 7mm. Convert it to a hole and align it with your box. Combine the two shapes. Now we have a cutout that we can use underneath our scale armor shapes, which will leave just the right amount of space for the light and the wires.

Drag it out of the way for now. Also, I always like to copy and paste my design elements so I have a backup of the original, in case I accidentally stretch it or lose track of it somehow.

Now it’s time to create the scales. You can use any shape you want, but shapes that nest together nicely are going to look best. Drag your shape out into your workspace.

Drag your light cutout hole into the middle of the shape and mess around with the size until it looks the way you want and fully covers the light dome while allowing the wire cutouts to extend on both sides. The align tool is useful here to get it just right.

TinkerCad has a lot of great shapes to choose from, but they’re all pretty simple and basic. I want a rounded top to my heart. TinkerCad doesn’t have a tool for this, so we’ll have to get a little clever.

Drag another half sphere onto your workspace. Think of this as a slicing tool - whatever sticks out the top of your half sphere will get sliced off. Move and drag and align until you get something that looks the way you want. Experiment — you can always redo this if you don’t like it.

Drag a box over your half sphere so that it’s completely covered and the bottoms are aligned. Change your half sphere to a hole, then group the box and sphere to make a cutout.

Change this new cutout shape to a hole, and group it with your heart shape to round off the top. Be sure your NeoPixel cutout still fits inside.

I want a little more variation in my armor so I’m going to make three slightly different sizes of hearts, just to make it look more interesting. I’ll copy and paste and then resize by a couple millimeters. I’m going to keep the thickness the same for each size for this project. If the heart is too thick, the light won’t shine through quite as well.

Make sure your light cutout still fits nicely under all sizes.

Align and combine each heart with a light cutout. I still like to keep one in the corner, to copy from.

This is a great time to stop and do a test-print, to make sure you’re happy with the different sizes, and that the lights fit and shine through nicely.

Once you’re happy, it’s time to start creating your scale pattern. Use copy and paste to align your scales the way you want.  If you’re using the 2” pitch lights, try to keep the cutouts slightly less than 2 inches apart from each other so the lights reach from one scale to the next scale easily.

Group all the scales together, then export them as an .stl file to send to your 3d print software.

I’m using Cura as my slicing software. Import the model and choose your print settings. You’ll want to print without support. We also want to tell the software to pause at about 2 millimeters so we can add the mesh fabric in. In Cura, you can do this under the Extensions menu option.

I’m printing in glow in the dark or clear PLA, since I’ve found that lets the light through the best. Start your print job and it will pause at 2 mm. Secure a piece of mesh fabric firmly over your print bed with tape or clips, then resume the print.

Once it’s finished, use a knife to carefully slash the fabric in all the holes, to make room for the NeoPixels. Use hot glue to press the pixels in place.

Add some code and a battery, and enjoy your glowing scale armor.