Cold Chamber Machines vs. Hot Chamber Machines

The Basics

Those who aren’t involved in the industry typically have a generic understanding of die casting.  For many, it might only go as far as being familiar with the key terminology, such as knowing that the mold is referred to as a die.

Expanding on this concept would explain that the die acts as variable element, and is injected with molten metal.  This process is generally done under high pressure, exerting the force on the die.  The molten metal can be injected two different ways, the difference between the two is referred to as Hot and Cold Chamber processes.

Cold Chamber Machines

Materials Used: Alloys – Aluminum, Brass, Copper

Temperature: Materials with high melting points

Chamber: Cylindrical Sleeve, Automatic or Hand Ladle

Closing System: Hydraulically Operated Plunger

Process: Cyclical

Premier Die - Cold Chamber Photo


As the molten alloy is poured into the cylindrical sleeve, the hydraulic plunger pushes the alloy through the system and seals the opening in the cold chamber port.  While the alloy is enclosed, the molten metal is forced into the cavity of the die under high pressure. Depending on the product, a die can take as little as a few seconds to solidify, or up to a few minutes (smaller products usually take a few seconds, while larger more complex products require a longer waiting periods, time is based on weight).  The design of the cold chamber system has multiple cavities that may contain duplicate parts or multiple different parts. This means that several parts, similar or different, can be made in one cycle.

Hot Chamber Machines

Materials Used: Alloys – Zinc, Copper, Magnesium, Lead

Temperature: Materials with low melting points

Chamber: Gooseneck

Closing System: Plunger

Process: Ongoing

Premier Die - Hot Chamber Photo


Hot chamber machines use a variety of metals, as long as they have a low melting point.  A key factor of these alloys is that they will not ruin or erode any of the machine parts they come in contact with during this process.  As the metal is injected, it travels down the gooseneck and enters the hot chamber (usually a metal pot suspended into a pool of molten metal).  The port at the top of the machine corresponds with the plunger, dictating the amount of molten metal that is poured.  As the port seals, the metal settles into the cavity where it will solidify, once the plunger retracts the casting is ready to be removed.

By Leonard Cordaro, President of Premier Engineered Products


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