Are these the same? I was reading an old CTT article from 2000 that stated '39 different locomotives'
came from the same die. I can see the similarities amongst many locos, but I get a bit confused when
the author, John Grams, states how the 'die' was modified to make different locos. Is the die(mold)
milled to have different details? Can details be added back in? Does anyone have pictures or a link
that explains exactly how this is done?
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You can have modular tooling, mold inserts that can be swapped out to produce different details on the resulting "shot". Sometimes a mold is physically modified to add or subtract details, such as postwar boxcar tooling was modified to subtract rows of rivets in order to make decoration easier.
Die casting generally refers to casting with metal. Injection molding usually refers to casting with plastic. In both cases the material is injected under pressure.
In the postwar era, different models can result simply from differing levels of add-on detail, such as different siderods, whether the tender has a whistle or not, type of tender, and presence or absence ot Magne-traction.
---PCJ
Fundamentally the processes are the same, but the machinery and tooling differs. In both processes, the casting media goes into a mold or die.
Die casting generally refers to liquid metal casting and it came into vogue for making precision automobile carburetors out of Zamac. The hot liquid metal is feed into a die by gravity or injected under pressure. The modern process uses powdered metal which is melted internal of the process. In the old days the metal was melted externally.
Injection molding is more versatile, and it came of age with plastics. Pellets are melted and injected under pressure into a mold. Powdered metal is also used.
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