These are airless bouncy balls that you can 3D print. They are each about 6 centimeters in diameter. There are three different deigns to choose from: Hex, Trig, and Node. While all three options are relatively stiff, Trig is the stiffest design and Node is the least stiff option. But they all bounce about the same. When printing, use supports for at least the very base of the balls. The Node design does have bigger overhangs, so you may want to consider using more supports for that design.

This was designed to work with 90A PEBA filament, and it bounces super well. I have also tested 90A and 95A TPU, but I found that using TPU just results in a dead bounce. If PEBA is too expensive for you, you can try using one of these other filaments: PCTG, Flexible PLA, and PLA-HR. I haven't tried any of these, but they may still work.

A 3MF project file is also provided for Bambu Studio that prints with the settings that I used.

Print Settings

I recommend using 90A PEBA

Use supports for at least the base of the balls

3 wall loops

100% infill (However, if you are using PCTG, Flexible PLA, or PLA-HR, you may want to use a lower infill percentage)

Slower print speed for a higher quality print