View A Video on Die Castings - A Quick Introduction
Die casting is a metal forming process in which molten metal is forced
into mold cavities under high pressure and then cooled in order to form
solid metal parts. Facilities where die castings are made are referred
to as foundries. Die cast products are typically made from non-ferrous
metal castings such as zinc, aluminum, copper, magnesium, lead, tin,
bronze and some alloys; alloy tool steels may be formed through die
casting as well, although the preferred fabrication method for steel
parts is forging.
For many years, die castings have presented a cost-effective and highly versatile alternative to other metal shaping methods such as forging and hand tooling. Die casting designs are capable of reaching much closer tolerances and far more complex shapes than forgings or stamped metals while requiring minimal secondary tooling and processing. Die casters can manufacture large quantities of aluminum die castings, zinc die castings and other metal castings with exceptional detail, surface quality and dimensional consistency at relatively low cost. Die castings are manufactured by hot chamber or cold chamber die casting, under carefully controlled pressures. The demand for die castings, particularly automotive castings and other castings used in industrial products, is very high throughout the world.
Many manufacturing industries use die cast parts both in their products and equipment. Since the advent of cost-effective plastic formation processes like vacuum forming and injection molding, the prominence of die cast metal shapes has diminished somewhat. For example, store cash register housings used to be made almost exclusively of die cast metal. Today, almost all cash registers are made of molded plastic. Despite this shift, the number of industrial, commercial and consumer utilities that are products of die casting is too large to be accurately counted. Parts that require the strength of metal still use whole die cast parts, such as gumball machine bases, sink faucets, gas pump handles and a wide range of other metal parts. Computer and electronics industries use high tolerance magnesium die castings as housings and interior EMI enclosures as well as miniature zinc die cast parts for various electronic equipment applications. In the automotive industry, almost every engine block is a die cast product. Die cast aluminum valve covers are also very commonly applied in automobile engines. Cast zinc products are also widely used as door and cabinetry handles.
Every die cast metal part is formed in a die. Dies are also sometimes called molds, and every mold is specially designed for shaping metal in a certain way. For closed die castings, which are the majority of castings, this mold is cut into two separate metal blocks; in order to form a complete mold, the tooled blocks are placed together with cavities aligned. Once the die has been created, it is sprayed with a lubricant that helps control its temperature and assists in part removal once the cast is complete. The die is then closed, and molten metal is poured into the shot sleeve and injected into the die under high pressure by a plunger. Pressure is maintained within the die until the cast has solidified, then the die is opened and ejector pins push out the solidified "shot." This metal piece is considered a shot until the excess material that has solidified around it during casting is removed. This excess material typically consists of sprue, gate, runners and flash that have formed in channels leading to the die mold and possibly in leakage areas between the mold cavities. The cast part is tooled and deburred to remove this excess and is sometimes put through additional secondary processes such as surface finishing, plating and CNC machining.
Die casting is a high volume, low cost means of forming relatively complex metal parts. Because this forming method does not create a uniform molecular structure or grainflow in the same way that forging and extruding processes do, die cast parts do not have high strength and often have microfractures and grainflow inconsistencies that can lead to part failure or breakage under strain, corrosion or heat stress. For this reason, die cast parts are often heat-treated and carefully tested after manufacturing. There are some cases in which a die cast metal part is less appropriate for a task than a forging is. Consistently, though, die castings can be applied and relied on for their strength and durability if installed and maintained correctly. It is also important to carefully pair the correct die casting with its application; choosing the wrong metal for a die casting application can be catastrophic, particularly when it comes to engines and heavy machinery. A combination of careful design, materials selection, installation and maintenance will ensure the continued reliable operation of a die cast part for many years.
Images Provided by A&B Die Casting.
Images Provided by Crown Die Casting Corporation
Die Casting Types
- Alloy castings are metal shapes made by a metal formation machine called a caster. Alloys are combinations of at least two metals and sometimes non-metals like carbon and silicon.
- are die castings made from aluminum.
- are commonly used in the production
of hardware and tools because of the great resistance of aluminum castings
to corrosion and high temperatures as well as their conductivity.
In addition, aluminum castings are used in applications requiring the
production of intricate part features and components.
- Automotive castings which include engine blocks and cylinder heads as well as
brake and suspension components, are increasingly
manufactured out of lightweight material, such as aluminum, to economize
fuel consumption by decreasing the overall weight of the vehicle.
- are used in the architectural and construction industries
and in decorative applications, such as doorknobs.
- are used in applications requiring high strength,
making them ideal for use in the architectural and construction
- Cold chamber die castings are cast metals that are formed in a cold chamber as opposed to a hot chamber.
- are used in applications requiring exceptional
strength and resistance to corrosion. Copper castings consist
of brass and bronze castings.
- shape metal by putting pressure on molten metal in a die.
- Die casting design is the process of planning and deciding the configuration of a die cast product.
- are produced by pouring molten aluminum into
a metallic tool at a casting temperature of 750º. Gravity
die castings have good tolerances and surface finishing.
- have very thin walls. The metal enters
the die cavity at high speeds and under great pressure,
which increases the chance of porosity.
- Hot chamber die castings are cast metals that are formed in a hot chamber as opposed to a cold chamber.
- offer great corrosion resistance and are used in
the production of parts in the plumbing industry. Lead
castings and tin castings also provide close production
tolerances but are generally
not as strong as other die cast metals.
- are formed when metal from an airtight
furnace is transferred into a metallic tool through
a rising tube. Low pressure
die casting is suitable for relatively small lot sizes
and for applications in which heat treatment is needed to improve
- are particularly useful in applications where
weight is a factor. Magnesium die castings are very
lightweight and cost-effective, especially in comparison to other
- are metal impressions made with molds.
- Pressure die castings are metal castings that have been formed under carefully controlled pressure conditions; all die castings can be considered pressure die castings.
- are often used in the production of small parts
for the electronics and automotive industries.
Zinc castings lend themselves
well to secondary operations such as painting and
Die Casting Terms