Metal vs Plastic vs Resin etc. (longish)

Metal moulds for plastic figures do indeed cost more than vulcanised rubber
moulds used for making white metal figures. However the cost of the mould
varies widely, depending mainly on the type of plastic being used and the
expected life of the mould. Some plastics - I believe the 'cheaper'
types
are very corrosive in their semi-liquid state. Moulds for short runs can
be made from ordinary tool steel and only cost several hundred dollars for the
metal, plus a few squillion for the cad machining and expert finishing.
This is the type of mould that used to be used for give-aways in cereal
packets. I rather suspect Gallob et al work on this principle - they get
a licence for 'x' hundred thousand units, when the licence quantity is filled,
chuck the mould away.

High quality moulds, especially for styrene, have to be made of special grades
of corrosion resistant tool steel which is apparently a near monopoly of the
Japanese steel companies. Needless to say, the cost of machining and finishing
goes up. These mould are good for long runs with good detail, however they do
wear which is where you get "flash" on the moulding after a while.

There is also no guarantee that the mould will not break at any time, which
means total loss. $$$$$

As for resin, the moulds are either silicone rubber, which does not need a
release agent, or flexible urethane which does need a release agent. The
engineering costs are negligable but the materials cost is greater than
vulcanised rubber for white metal and the mould life is shorter than a rubber
mould used with white metal.

An acquaintance who was involved in high quailty moulding of resin vehicles &
aircraft said the preferred material is silicone rubber, and that the
mould is only good for 75-100 high quality castings with the urethane
resins that are used in their models. Apparently a reaction to the catalysing
resin which releses cyanide just like 'Super Glue'.

Another friend in the movie props buisness used the urethane moulds, but his
models are sand blasted first before 'dressing' and painting. The resulting
models pass the 6 foot test easily, some of them pass the 1 foot test.

Rubber and resin moulds can be relatively easily replaced as long as you have
a master figure to work from.

regards