How to remove that line (showed in fig) in sheet metal without loosing the rings and it should be flatten.
I thought you were going to understand with my example that to create a network modeled for you. : UNFOLDABLE POLYEDRA
Note that you will have some limitations of material thickness as a function of the bending radius and other parameters of the sheet metal function. In the example that I enclose, I proceeded with thickened surfaces and converted into sheet metal. But it would be better to proceed with the bend-to-edge function that will give you more flexibility. So your network of circles must join with a minimum straight section related to the thickness of the material to obtain a polyhedron after folding. Also, it should be known that a unfolded polyhedron has cut edges and welded edges.