For making samples of the repeated spheres structure, I did electric forming to ping pang balls to be a large size model. But I still need small samples to experiment that whether the structure works or not. This sample should be as detail and regular as possible, even using simple materials.
I used Jossi Press cut the 0.7mm aluminum sheet into 20mm dia rounds, then used dooming block to hammer them in to the half sphere as I sketched.
Aluminum is not a good material for doing this, cause it has bad ductility compared with other metal. But I choose it because it is lighter. There would be repeated spheres in this structure so the material need to be light.