What does diecast mean?

What does diecast mean? Does diecast mean metal? Diecasting is a manufacturing process involving a metal alloy and a two-part mold, called, predictably, a die. It was originally invented in 1838 for creating moveable type for printing presses. But in the 20th century it became popular for making other goods, especially toys.

Diecast, in the modern meaning of the word, refers to materials made specifically of zinc alloy and cast in a mold. It’s an inexpensive process that yields very good detail and strength.

What does diecast toy mean?

what does diecast mean
Some diecast toys, notably Mattel Hot Wheels cars, say “die cast metal” right on the package.

Diecasting is probably more closely associated with toys today than anything else. Most modern metal toys are diecast today, if only due to safety reasons. Diecast toys don’t have sharp edges and they don’t contain lead.

All diecast toys are metal, though not all metal toys are necessarily diecast. The process became common in toymaking in the 1920s and grew in popularity throughout the 20th century because it allowed finer detail than making toys from sheet metal, greater strength than casting from lead or pewter, and didn’t rust.

Pot metal vs diecasting

Pot metal refers to a process where a mix of nonferrous metal is melted, originally in a pot, and then poured into a mold. Die casting is a form of pot metal, but the two terms aren’t completely interchangeable. Usually when people refer to pot metal, they mean a cruder process where not much care is given to what metal ends up in the formulation.

In modern diecasting, the formulation is important in order to get a long-lasting product.

How the process works

The process involves a mold, made of metal, in two halves, called the ejector die and the cover die. A large machine injects molten metal, usually a zinc alloy, into the die using pressure. After it cools, the two halves split apart, freeing the cast part.

Advantages of diecasting

Diecasting allows a great deal of detail in very inexpensive metals. The zinc alloys used in diecasting are relatively lightweight and strong for the cost. Mattel has been able to hold the retail cost of its Hot Wheels cars near the $1 mark for decades partly because of the low cost of materials.

The process allows for very smooth surfaces and thin walls, which helps both production cost and capturing fine detail. The part needs minimal finish work after it comes out of the die, compared to other molding processes. A small line, called a parting line, can appear where the two mold halves met. This requires some filing or grinding to smooth away. But the rest of the surface requires no finish work before painting.

Disadvantages of diecasting

There are some disadvantages to diecasting. The biggest problem is the tooling cost. The dies are expensive to produce, so diecasting requires huge volumes to reach reasonable economies of scale. This is why a Hot Wheels car can retail for a dollar but limited-run diecasts in 1:43 scale may sell for $200. This is also why toy companies reuse the same tooling over and over again for decades, such as Lionel continuing to use locomotive tooling it produced in the late 1930s even today. Even Mattel puts Hot Wheels cars back into production decades after their initial release, just updating the tampos and changing the wheels to give the cars an updated look.

Diecasting is also impractical for items that weigh more than 20 pounds (10 kg). This limits its usefulness to smaller items, though certainly not just to toys. Screen door handles, for example, are diecast. When die casting is used for large, heavy items, like engine blocks, it is limited to smaller parts weighing 20 pounds or less, which later are assembled into the whole.

There’s one other disadvantage to diecasting, or, specifically, to the Zamac alloys used in modern diecasting. Zamac’s formulation is a bit touchy, and it can crumble over time if there are impurities in it. This problem is known as Zinc Pest, or Zinc Rot. The solution was widely known by the 1930s and 1940s so it’s rare today, but sloppiness in the supply chain can re-introduce it.

History and adoption

The process of making the dies is expensive and requires skilled labor, so it gained adoption in countries like Germany, the United Kingdom, and United States first. Today the process can be fairly cheap, and diecast toys can be cheap enough that people use them as party favors, but in first half of the 20th century, it was a premium process. Over time the process moved east, and today, the process is very common in the Far East. Initially manufacturing moved east to get lower labor costs, but certain countries have specialized over the years. South Korea, for example, is generally able to produce higher quality tooling today than western countries, while beating them in price. Chinese production, meanwhile, is still driven by price. Sometimes companies will contract the tooling to a South Korean company, then ship the tooling to China for manufacturing.

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