"shantia" wrote in message
...
in fact we have called some , but no one accept the risk of it.

they just suggest to thinking on roll forming , spin forming ,
stretching or a mixed up of them!

Too bad. Roll forming is a very tricky thing when you depart from a few
standard shapes, as we've discussed. Ram-forming or some kind of
mandrel-stretching probably would be the way to go if you were making a lot
of them, but I can see the tooling costing $100,000 or more because of all
the constraints that would be required to prevent twisting and wrinkling.

Conceptually, it could be spun, but it would require an enormous specialized
lathe (probably a custom-built VTL) and I've never heard of such a thing,
except, in photos only, some machines built for the rocket-engine business.
Even there, I have no idea if they could handle making a bell-type expansion
in 15 mm stainless. The superalloys used in some rocket parts really aren't
that much different in terms of properties, at room temperatures, than some
grades of stainless. They're generally high-nickel, high-temperature
"superalloys." And I don't know where those machines would be today. Pratt &
Whitney Aircraft probably would know.

Can you tell us what the application is, or is it a secret?

--
Ed Huntress