My niece has Special Needs and sucks/bits her thumb. This guard tries to prevent some wear and tear on her thumb. I used 95A NinjaTec Cheetah TPU to print. I used support and a raft only for the first few layers(to support the bottom curve along the wrist-end). There are commercial products but they are expensive and don't fit well.

I scanned her hand and forearm in with my iPhone using an app called EM3D. Proper light is key to a good scan. 4000K, 95CLI, worked for me. Positioning her on a table laying flat, with her arm hanging down over the side was the easiest way to keep things steady. I rotated around her arm.

Once I got a good scan, I tried many different CAD/Software packages. Blender proved to be the most capable for the amount of verts. After working with the hand model, and learning Blender, I was able to come up with what you see here.

The Voronoi pattern used allows for structure, breathability, and a little bit of stretch so the fit around the widest part of her hand can be accommodated without it being too loose.