Paul,
I've spoken to 3 Investment casting foundries, one quote was

$21,000

one

was

$10,000 and one was $5,000 - rough estimates only.
These were for cast steel moulds and from talking to them I've

worked

out

how they do them, which is just a couple of more steps than what

I've

done

so far.
One - make a cast of the pattern
Two - make a sand mould then pour your steel.
Three -  clean up the steel mould.

Two steel moulds would be required one front face and one inside

face.

Most of the cost is in the time - which I have.

It's something to think about, however finalisation of the

design is

necessary and some more research !

These would be gravity castings and as such still require a

minimum

of 4

mm.

One draw- back with a steel mould for thin sections, the air

tends

to

get

trapped.

George (down under)

I am a bit confused. What you are descriping appears to be

"permanent

mold"

castings rather than investment casting. A form of investment

casting

being

used for aluminum parts in the auto industry is "lost styrafoam"

castig.

This
removes the need for draft, and the foam can be made in wood or

composite

molds and assembled with "trapped areas"
Vance

Vance,
It was obvious to me when I went to the US we call things by different
names.
Mind you I'm new to this, but it appears to me that everyone else (here)

is

using the term 'investment' as an indication of the large dollar value
invested in a permanent mould.

A permanent mould (gravity fed) has it's advantages and disadvantages.
The big advantage is that you get exactly what you want everytime.

However

very thin areas are still a problem, as well as trapped air.
The perfect solution is pressure injected mould - I can't afford that

given

our numbers are relatively low.

I haven't looked at the lost Styrofoam yet, the elimination of draft has
it's attraction, however it may need a permanent (expensive) mould to

blow

the Styrofoam.
Thanks for the suggestion!
George (down under)

Typically the term investment casting  involves the loss of the master and
the
mold, as in "lost wax" casting The wax is burned out (vaporized) in the
invstment
plaster. The molten metal is poured, centrifuged, steam pushed, etc into the
plaster
and then the plaster is broken from the part. Properly accomplished this
provides
incredible detail in the finshed part. A version of this is often used for
the
super alloys for turbine blades and such. The lost styrofoam is usually done
in
sand, and the molten aluminum vaporizes the foam as it is poured in. On some
engine blocks you can even see the "foam cooler type balls " as a texture on
the cast surface. - Vance

The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2003 All world wide rights reserved.