Quick Facts

The wide range of products that can be die cast, the close tolerances that can be readily held, the accuracy of reproduction of detail, and the economy and speed of manufacture are significant factors in the popularity of die casting.  Die castings are distinguished by their characteristic accuracy, smoothness, and good surface quality.

The Process

Die casting is a repetitive operation wherein identical parts are cast at maximum production rates by forcing molten metal under considerable pressure into metal dies.  Die halves are securely held together by the die casting machine clamping mechanism in order to withstand high pressure.  The metal chills rapidly in the die.  When the metal has solidified, dies are opened to eject the hot casting.  The die is closed again and the casting cycle is repeated.

Die Casting Advantages

Among the advantages of die castings: 1) Parts die cast are almost completely finished units and can be produced at high production rates.  Little clean-up is required; 2) Dies used in die casting, while initially expensive, have relatively long wear life and, because of the large production volume, mold cost per casting is usually lower than for other casting processes; 3) When large quantities are required, die cast parts generally cost less than castings produced by other processes; 4) Little draft is required; 5) Dimensional tolerances on each part cast are more closely held than is generally possible with other major casting processes; 6) Generally a surface finish of 63 rms is readily obtainable.

Die Casting Disadvantages

The major disadvantage of die casting is the potential for air or gases in the die cavity to become entrapped in the casting and form voids.  These gas holes lower the mechanical properties of the casting; if near the surface, they may cause blistering during subsequent thermal treatment.  Additionally, tool modification is costly.  Also, coring is generally restricted to shapes permitting straight core pull.

Alloys

Lead, tin, zinc, aluminum and magnesium alloys are commonly die cast.  Some copper base alloys are also die cast.

Tooling

Dies generally are made from hardened tool steels.  Steel properties, of particular importance in casting dies, include a high degree of resistance both to thermal shock and to softening at elevated temperatures.

Design and Technical Information