Thermoformed Pattern 3D Bracelets

A few years back when I taught middle school CTE I was asked to teach an art class. Not knowing much about art I did my best to teach the class while incorporating what I did know, 3D printing. One of the ways I did that was by having students create bracelet designs using various pattern drawings that they created. By converting their drawings to SVG files, students could use Tinkercad to turn that pattern into a bracelet. We then could 3D print the flat bracelets, and use hot water to thermoform them to the desired shape. This ended up being a really interesting project. This tutorial goes over this process.

• Devices capable of running Tinkercad
• White paper
• Black markers
• Phone for scanning drawings
• Image to SVG converter (online)
• 3D printer
• PLA filament multiple colors if possible)
• Hot water
• Container for holding hot water
• Tongs
• Safety glasses

The first thing you need to do is determine how big you are going to make the bracelet. This constraint is partly based on the size of your 3D printer print bed. Your design cannot be bigger than your print bed dimensions as we are going to print these bracelets flat. For example the Makerbot build plate is 11.6 X 7.6 inches so the total bracelet design must fit within that area.

• These bracelets examples are about 1 inch wide x 7 inches long. And about 0.1 inches thick. I kept the size relatively small because we had to print many of them in class.
• For this example going forward we will use a 1 inch x 7 inch rectangular size limit.
• You could make much wide bracelets but keep in mind it will use more material.
• You can determine the approximate diameter of your bracelet based on the length of your design.
• Length of the design = circumference of the bracelet
• Diameter of the bracelet = Circumference / pi
• For example if I design a 5 inch long flat bracelet I can determine that the diameter = 5 inches / pi = about 1.591 inches.
• Keep in mind all of these bracelets will be "open-ended" so you could make a larger diameter bracelet with a gap at the ends as well.

Next you must determine the shape/style of bracelet you want to create. Each of these examples was printed with a solid background color piece. This was done to not only help with the contrast of colors but also to help the pattern maintain it's form later when thermoforming. You could also create a bracelet solely from the pattern design without a solid background, but it may be more difficult to thermoform consistently if the pattern lines are thin. It may require some experimenting on your part.

• This is also dependent upon your printer. If you have a dual extruder or if you are able to pause and change filament mid-print, you can create these multi-colored layers.
• If you do not have the ability to do this, you can still create a solid background just to make forming easier.
• Single color designs could also consist of a pattern being debossed or cut into the solid layer.

The shape doesn't necessarily have to start off as a rectangle either. There are many possibilities that you could create.

In the past I had my students complete this step on paper as it was done in an art class. The instructions below are written for paper but you could always use online tools that are available or even Tinkercad to create the pattern. I personally liked having students draw their designs on paper though as it was a better challenge and led to a more unique product.

1. Use a blank white paper with no lines or marking
2. Use a dark color marker. black is best.
3. The drawing is a basic line pattern of some sort. Shading, contrasting, etc. will not translate when converting this design to an SVG.
4. Once you know your size limits, draw your pattern within those limits.
5. You can draw the pattern larger if needed and scale it down later in Tinkercad.
6. If the pattern does extend past the size limits, that is okay. you can cut off the excess in Tinkercad.
7. Small parts of the pattern can be created also and then duplicated in Tinkercad (like the small swirl drawing)
8. Know the limitations of your printer. Some dots, thin lines, etc. will likely be too small for your printer to replicate.

Once your pattern is done to your liking, you must now scan it or take a picture of it. I simply did this with my Iphone but you may have other methods.

• The goal here is to get the cleanest, clearest picture of your pattern that you can get. The clearer the picture is, the easier it will be to convert it to an SVG file.
• You do not want shadows or highlights on the page when you take the picture. You will need to determine the best way to get the image that you need.
• Get the image onto your device and then move on to the next step.

There are many online converters that you can use for this. You are trying to convert your image file to an SVG file. The SVG file can be directly imported into Tinkercad.

I like this converter: https://convertio.co/jpg-svg . It is simple and easy to use and I rarely have any issues with it. But there are many others.

The step-by-step instruction for creating the model in Tinkercad are below also. Again, you may have to deviate from these instructions if you decide to do a different style of design that is not so simple and rectangular.The videos have no audio.

1. Create your "background" layer. Using the dimensions you determined earlier create the basic shape of the background piece. I would make sure any sharp corners are removed (as you can see in the example pictures the corners were rounded off)
2. Import the SVG of your pattern design. You may need to scale it down to fit it in the Tinkercad model, this is not a problem.
3. If you have any trouble importing the pattern design, you may need to try taking a new picture with better quality or converting the image again.
4. This video linked here shows a quick version of importing and modifying the design.
5. Resize the pattern so that it will fit onto the background layer. Make sure the pattern is connected to the background layer and not "floating" above it.
6. Trim off any excess. Do this by creating a hole shape that matches the profile of your background piece. Use this hole shape by grouping it with the pattern to cut off any excess. This video linked here shows this process.

Export your design as an STL file and 3D print it using your printer. This is not a tutorial on how to do dual extrusion or how to pause a print to change the filament color. There are plenty of resources out there for that. Follow your printers procedures to create the flat 3D printed model.

This method will work best with PLA plastic. Some other filaments may not be as easy or safe to work with.

The last step! (and most fun in my opinion).

Now it is time to turn the flat design into an actual bracelet.

Note: While PLA is generally considered safer than other filaments, I would still recommend doing this process in a well ventilated area. We are still talking about heating up plastic material so better to be overly cautious in my opinion.

1. Boil enough water to fill the container you will use for this process
2. Carefully place the bracelet into the hot water. Use tongs!
3. How long the bracelet must remain in the water will depend on a number of factors like the thickness of the design, type of filament, etc.
4. Anywhere from 10-15 seconds will probably make it pliable enough to form.
5. Remove the bracelet from the water with tongs. Carefully shake of the excess hot water. Let it cool just enough so that you can handle it with your hands without hurting yourself
6. Form the bracelet around a cylindrical object of the desired diameter. (You could 3d print a cylinder if you can't find an object that meets your requirements!)
7. If you are going to form the bracelet around your own arm/wrist, make sure it is cool enough that it will not burn you. I don't recommend doing it this way as it will also be a less uniform circular shape.
8. Once the bracelet is formed to your liking, run it under cold water for a few seconds until it maintains its form.
9. You can reheat and reform the design as needed!