[Calico]

I have CNC mill machine.
check this Graphicast Process and Products Are A Cut and Design Above

that company makes permanent mold using graphite, looks high quality.

if I use lost wax, meaning I have to buy the oven, I wonder which plaster recommend ?

[ihavenofish]

that company casts one single alloy and provides no information on the mould composition and only a few small blurry pictures of them.

most likely they use graphite in a binder for strength and nothing like the typical stuff you can buy. it also may only work well with the one zinc alloy they use.

for lost wax, you need something to heat the mould boh to get the temperature up and to purge moisture, and also to burn out the wax. but there are several ways of doing it that dont require much gear. we usually use steam for glass moulds to remove the wax. the steaming device is a glorified tea kettle. with the right wax, you get a nice clean mould. for heating, you can then stick it in the kitchen oven. with the wax 99.5% melted away already, you wont get much fumes.

on the plaster, there are several special purpose investments most being developed for stability at high temperatures. for aluminium, you could use almost any fine plaster. its pretty easy.

[awerby]

I wouldn't advise pouring aluminum in a mold that had only been burned out in a kitchen oven. All traces of wax and chemically-bound water have to be gone, or you risk creating a volcano which will spray molten metal all over the place. This requires temperatures of over 1000F; much hotter than any kitchen oven gets. You need a kiln for this. Glass might work differently.

Also, you can't just use "any plaster" without mixing in some kind of refractory aggregate. Investments for lost-wax casting of metals usually consist of one part gypsum plaster to two or more parts sand or silica flour, although other refractories can be used.

[ihavenofish]

for glass the mould is heated to 1500f with the solid glass in is.

yeah, kitchen oven may not get hot enough to do it right.

[Calico]

yup agree with you guys that lost wax is not that cheap and simple.

I'm thinking replacing the "lostwax" on the centrifugal casting with Graphite mold (2 pieces).

you got my idea ? will this work ? of course I have to heat the graphite before turning the centrifugal.