Often when working on projects, I am forced to use a close match of a part instead of the right sized part for the job. The beautiful thing about 3D printing is the ability to customize an object to exactly how you need it. With some basic 3D modeling skills, you can create a part to your desired specs and have it printed before a commercial company could have even received your order.

This Instructable will demonstrate how to create custom sized rubber bands using NinjaFlex flexible filament. Custom rubber bands could be useful for a wide variety of purposes- from precise pulley/belt systems to the perfect sized bread tie (no more stale loaves!).

Step 1: Tools and Materials

Before you begin, collect the following:

3D printer- capable of printing NinjaFlex. I printed an addon for my Printrbot Simple that allowed me to use flexible filament.
NinjaFlex flexible filament- I got a sample pack with a broad range of colors from here.
3D modeling software- I will be using Autodesk Inventor Student
calipers (recommended)

Step 2: Measure

You will need some dimensions before you design your custom sized rubber band. Use calipers to measure the diameter of the rubber band application. Consider the fact that the rubber band will be able to stretch. I decided to make my rubber band diameter half of the diameter of the final application. During this step, you will also want to decide how wide and thick your rubber band will be.

Step 3: 3D Modeling

Time to start 3D modeling! Start a new 2D sketch in your CAD program and draw a circle to the diameter you identified in the previous step. Offset this circle by the desired width- I chose to make my rubber band 3 mm wide. Finally, finish the 2D sketch and extrude the offset shape by the thickness that you want your rubber band to be. Mine will be 4 mm thick.

Now you have a 3D model! Export your design in a 3D printable format such as a .stl file.

Step 4: Print!

Print out your design. Since we are using Ninjaflex, I would suggest using slow speeds to avoid extrusion issues. Since it is so small and simple, the print should take very long. Here are the settings that I printed with:

Ninjaflex Filament
.3 layer height
100% infill density
30 mm/s speeds

Step 5: Enjoy!

And that's it. You now have the ability to create custom sized rubber bands to suit any application. I encourage you to treat this Instructable as both a project and a concept. The project is creating custom rubber bands. The concept is the fact that you can create practically any custom part with a 3D printer; take some dimensions, design on a computer, and print out your desired part.

I hope that you enjoyed this Instructable and will try it out. Please let me know if you have any suggestions or questions.