On Wed, 03 Oct 2007 16:30:28 -0700, Eric R Snow
wrote:

On Wed, 03 Oct 2007 07:31:51 -0700, Bill
wrote:

Hi

I need to build parabolic dishes of different shapes. I think that
spin forming should be the ideal method but I no nothing about that
method. I'm not a metal craftman.

I have some questions about that process.

The material I want to use is either cupper or aluminium. Thickness is
in the order of 20-28 ga.

I don't want to make a mold for every dish because I won't produce
many of each size & shape so it has to be "turned" on air.

Is spinning on air precise enough to produce an exact curve every
time ?

What should be the rotation speed of the machine for let's say a 2-4
feetd dia. dish ?

Can I use a modified small lathe for that or a simple spindle could do
the job ?

Thanks
You should google for metal spinning. There is also a yahoo group for
metal spinners. Whenever I spin something the part of metal being
"supported" by the air seems to almost always be conical. Sometimes I
get a curved shape that may or not be parabolic. But then I'm not
trying to get a particular shape in the air, I'm trying to get the
metal to conform to the chuck and it will take whatever shape it wants
from flat disc to fitting the chuck. Some production metal spinning is
done on CNC machines. Maybe if the material was consistent a tool path
could be programmed to get the desired shapes without too many scrap
parts.
ERS


We specialize in metal spinning for more info:
www.debcomachinery.com
Daveb