My dad is actually a metallurgist. He has an entire machine shop in his garage. He had the stop sign aluminum and, after I lost the argument about using plastic, he cut out the pieces with a nibbler. He shaped most of them with a pneumatic press and pieces, such as the chest plates and back plate, were fed through steel-rolling press until they were too curved, then mounted in a very large vice and hammered on until they were the appropriate shape.
It's not his first set of armor. He has an entire set of SCA armor hand made out of titanium, which was even more of a pain to work with. The difference is that he has the shop available to continually tweak pieces and I do not.
I have, in the year past, acquired a giant roll of black ABS that I can cut with heavy-duty shears, a dremel tool with plastic bits, and an actual heat gun. I'm pretty sure I'll be starting on a brand new set of armor right after I finish this one and chalk it up as a failure. LOL