In die-casting, liquid metal is shot into a permanent mold by means of a piston. Pressures can be very high, which permits the production of very thin-walled and complex components without any quality losses. The mold or die is filled within fractions of a second even when large parts are manufactured, resulting in short cycle times. As the complex dies (two-part permanent molds) are often made of tool steel, the process is suitable only for metals exhibiting a low melting point – such as aluminum, magnesium, zinc and their alloys.
Due to the high shot speeds of the process, air and gases can be entrapped, forming voids and pores. While these voids and pores are closed under high follow-up pressure, they can grow again if the castings are heated in any subsequent manufacturing step. For this reason, die-castings are normally not considered suitable for heat treatment and welding.
In sufficiently high-volume production runs, die-casting is the most economic of all casting methods.
The open shot chamber is filled with molten, liquid metal.
By means of an hydraulically driven plunger, the melt is shot into the casting die at a speed of several meters per second.
The melt solidifies under follow-up pressure in order to prevent shrink holes and porosity.
The casting die halves open, and the casting is ejected.
Finishing is normally limited to grinding off the sprue and removing any flash formed at the parting line of the die halves.