This isn't so weird really... Walking through a plastic injection mold shop, and you'll see many weird electrodes for EDM.
Plastic molds are made from hardened steel for longevity during the molding process. 50,000 shots to 200,000 shots...
Some plastics are more abrasive than others, so hardened steels are a must. For example, a glass filled polycarbonate plastic used for automotive, and other high strength applications needs that hardened steel, as the glass wears on the mold during filling.
Since the steel is hardened, it is much more difficult to machine features in.
The solution is to use an EDM machine to burn the feature into the steel using the electro discharge machine. The electrode is made from copper, which is easy to machine. The downside to the whole process is that it's very slow!!!
The steel molds get very expensive, especially for larger parts.
China tooling for small parts can be fairly economical... Around $5000 for small parts.
Complex and larger parts cause the cost to go up quickly... more tool steel, more machining, and a much larger mold press is needed during the manufacturing process. Those molds can cost over $250,000.... I know this first hand.
So the next time you see a plastic part... whether it's on kid's toys, or your computer... each one of those parts has a corresponding steel mold to make that part.
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