I would think twice about using Aluminum, as it is soft and
isn't that good of a heat conductor.
I assume you’re talking about vulconizer platens. Several
commercial vulcanizers use aluminum platens, as it is, in fact,
and EXCELLENT heat conductor. Almost all commercial mold frames
are aluminum for the same reason. Almost as good as silver. As
to it’s softness, that depends on what you buy. You can get
rolled machining stock from metals suppliers that’s nicely work
hardened, and won’t easy deform, yet machines beautifully if
that’s how your planning to build your machine or part. It’s not
steel, of course, but then it doesn’t need to be to work well.
Use mold plates, 1/8th inch sheets of aluminum larger than your
mold frame to face the sides of the molds in vulcanizing, and
you’ve equalized both the heat transfer to the rubber surface
and any unequal pressure that might damage the vulcanizer.
I use only Castaldo mold rubber, gold to be exact. It
vulcanizes @ 307'f, and the instructions say 7 min. per slice,
I do 10, it has worked for me, with no problems. Your
vulcanizer needs to be as close to the 307'f as possiable with
Agreed. Castaldo gold is good stuff. The white lable makes a
stiffer mold, though, which can be useful for flat items where
the soft gold might tend to make it harder to keep from
compressing the center of the mold cavity, and you don’t need the
flexibility of the gold label to pull your waxes. Both rubbers
make excellent molds that are very long lasting. but it should
be pointed out that in recent years, a number of other very
useful mold rubbers have come along as well. In particular, some
of the silicone rubber based vulcanizing products are very
interesting. Some of them produce molds that are just as
durable and flexible as the castaldo, yet are completely self
lubricating, with no need for sprays or other wax releases. Some
of them, if shaped to fit into a casting flask instead of a flat
injection mold, will even withstand the heat of white metals like
pewter, and can be directly used to cast such metals in your
centrifuge, with the mold being reusable for a great many such
castings. Still, for plain old wax injection rubber molds, few
pros use other than the Castaldo or the competing Kerr rubbers
(which are essentially similar).
You will also need pressure kinda like a press. Look at the
professional vulcanizers in the catalogs and you will
understand what I mean. When you put pressure and heat together
you vulcanize the raw rubber into a semi-solid form, or "cooked", rubber.
A vulcanizer is a great convenience for doing any appreciable
quantity of molds. But you can also use a home oven, if the
thermostat is accurate enough. The mold frame and rubber get
clamped between two sheets of steel plate (1/4 inch) instead of
the vulcanizer platens, with a C clamp or two to provide the
pressure. Sheets of aluminum between the steel and the rubber
will improve the even heating of the mold.