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Die casting is a highly accurate and efficient metal manufacturing process for industrial, commercial, and consumer goods. With tooling that lasts a very long time, die casting is suitable for the manufacturing of complex metal parts, offering great value when it comes to mass production.
Several metals can make suitable die casting materials. These are mostly non-ferrous metals (metals that do not contain a significant amount of iron) although occasionally ferrous metals can be used too. The main die casting materials are aluminum, magnesium, and zinc alloys, all of which have particular advantages and suitable applications.
This article looks at the best die casting materials, listing their respective benefits and common applications in the manufacturing world.
What is die casting?
Die casting is a form of metal casting, a family of processes in which molten metal is poured or forced into a mold cavity. There are many forms of metal casting, including sand casting (low cost), investment casting (low volume), and die casting (high volume). Casting processes differ in terms of their pattern types, mold types, compatible materials, and material delivery methods (e.g. gravity pouring vs high-pressure injection).
Within the metal casting family, die casting is particularly suited to high-volume production of complex parts. This is because it uses a permanent mold in the form of two tool steel dies. These dies are expensive to make — usually via machining — but last a very long time and provide value in the long run.
Die casting is employed across many industries in the production of industrial, commercial, and consumer products. Compared to other metal casting techniques, it is better suited to small or medium-size parts that require a good surface finish.
The die casting process
Die casting has a few variants (discussed in the following section) but the process generally follows a set routine.
Before die casting begins, a manufacturer must obtain two metal dies: the cover die half and the ejector die half. Together, these two dies form the tooling for die casting, and the gap in between the two die halves functions as the mold cavity. Dies are typically machined from hardened tool steel, which is highly durable.
The first proper stage of the die casting process involves preparing the dies for casting. This entails applying lubricant (usually water-based) to the cavity walls, ensuring that the castings will not stick to the inside of the dies. Lubricant also helps with temperature control.
The next stage is material delivery. In most die casting setups, the die casting machine injects molten metal into the mold cavity under high pressure — though the exact degree of pressure depends on the type of material and whether it is a hot-chamber or cold-chamber die casting machine. Pressure ensures that the material is forced into even the smallest crevices, and this pressure is maintained as the molten metal cools and solidifies to mitigate shrinkage.
After the metal has cooled and solidified within the mold cavity, the casting is ejected by opening up the dies and gently pushing the castings out of the dies with ejector pins. Another shot can be prepared immediately after the ejection, enabling rapid mass manufacture of identical parts.
The final stage of the die casting process is the shakeout stage, which involves cutting (manually or via special machinery) the excess bits of metal attached to the casting, including flash from the parting line and any gates, runners, and sprues (parts of the die design that allow molten metal to enter the mold cavity).
Die casting produces an excellent surface finish that does not require the same level of post-processing as, for example, machined or 3d printing parts
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