What is Die Casting?

By Chris Welsh
Wrenches, toy cars, parts for watches and blenders, the inner workings of many a mechanical marvel; what do they all have in common? They were die cast, a process of “rubber stamping” products in a uniform manner which typically results in high production or identical or nearly identical products. A die cast car, for example, can be made by the dozens or hundreds at a time, producing high volume yields with few, if any, quality control concerns. The process of die casting is simply injecting molten metal under pressure into steel molds. When the metal inside cools, the molds, or dies, are opened and the product is ejected. Viola, product “x” is complete.

The Details

There are two forms of die casting; the cold chamber process and, you guessed it, the hot chamber process. Each process is very similar, involving the idea of injecting molten metal at high pressure into a mold to make a uniform part or product, but different metals have different melting points, and so two processes had to be created to expand what die casting was capable of. In the cold chamber process, which is primarily used for metal such as Aluminum and Copper (and it’s alloys) that will alloy with Iron at higher temperatures. It is a slower process to fill the dies, where the molten metal is ladled into the molds.

The hot chamber process is for metals with a low melting point and a high fluidity, such as Zinc, Lead and Tin. This process uses pressure to fill the die cavity very quickly.

Setting up a Die Casting Process

The lead time on setting up a new process with a foundry can be many weeks or even months. There are limits to the size and complexity of die cast pieces, with two foot square topping the size chart, except in specialist cases with fairly large foundries. The costs are typically much greater than other forms of rubber stamp molding processes, such as those using plastics, etc. In the end, however, the process chosen for the product will depend on the product itself. Keep in mind that stronger metals cannot be die cast, such as Steel and Iron, which require different process to manipulate.


  1. A classmate recommended me to read this site, brill post, fascinating read… keep up the cool work!

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