The Differences Between Hot and Cold Casting
I have always imagined cold chamber die casting to look something like a scene from an old cartoon where the character is suddenly encased in an entire block of ice. I imagined the process froze the metal quickly into the shape of a mold. Of course, this is not really the case. Freezing hot metal suddenly can cause the metal serious stress and even cause breakage in the metal. Cold chamber casing does not have so much to do with adding cold temperatures to the metal as it does with carrying the melted metal from one machine to another for die casting.
There are several key differences between hot and cold casting.
In hot casting, the metal is heated and molded in the same machine. There is no time for the metal to cool at all, which is where the “hot” label comes from. The machine is in constant contact with the metal, which allows the metal to stay warm during the molding process. Of course, this can also present a problem in metals that have an extremely high melting point. These hot metals can actually damage some of the casting materials, which is where cold casting comes in.
In cold casting, the metal is heated and softened in a separate machine. The metal is then carried over to the die casting machine for additional molding and shaping. The metal is still hot when it reaches the die casting machine, but the metal is not as not as the initial melting point for the metal. This protects the die casting machine and prevents the extremely hot metal from damaging the delicate parts of the mold and machine. Of course, it requires additional pressure to mold colder metals. Cold casting machines typically use a high amount of pressure to force the metal into the molds. This makes cold casting more expensive than hot casting, because it requires heavier machinery and multiple machines versus the hot casting method, which can complete all processes easier in one machine.