well I think Ed is right , the conical part will wrinkle without any
doubt if I just use a simple roll forming.

but no one had seen how such part is created? I myself think of spin
forming , maybe shear spin forming or flow forming

the fact is we don't concern about the money , even about 16000 $ is
just fine , but we don't know investing in which way would be better.

as I mentioned before , casting is not allowed , it should be formed
from sheet.

once someone mentioned of machines used for making Saturn V rocket
nozzles , anybody know what machines do they use for that forming
process , I'm sure theire material is much more stronger than
stainless steel.