Die Castings Industry Information
IQS Newsroom Articles on Die Casting
Die casting is a metal forming process in which molten metal is forced
into mold cavities, or dies, under high pressure then cooled in order
to form solid metal parts. Facilities where die castings are made are
referred to as foundries. Die cast parts are typically made from
non-ferrous metals such as zinc, aluminum, copper, magnesium, lead, tin
and bronze; 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 more traditional methods such as
forging and hand tooling. Die cast parts 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 good detail, surface quality and dimensional consistency at relatively low cost.
Because complex parts can be die cast at high volume, many
manufacturing industries use die cast parts both in their products and
equipment. Before the advent of vacuum formed and injection molded
plastics, die cast parts provided the exterior shape of many common
products and consumer items, such as cash registers and parking meters.
Many modern parts which require the strength of metal still use whole
die cast parts, such as gumball machine bases, sink faucets, gas pump
handles and an exhaustive range of metal parts used in automotive and
industrial machinery. 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.
Before parts can be cast, a cavity must be tooled into the desired
shape of the part. For closed die castings, which are the majority of
castings, this cavity is cut into in two separate metal blocks; in
order to form a complete mold, the tooled blocks are placed together
with cavities aligned. This cavity is called a die. Once the die has
been created, it is sprayed with a lubricant which helps control the
die`s 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 considered a shot until the excess material which has
solidified around the casting is removed. This excess material
typically consists of sprue, gate, runners and flash which 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 as forging and extruding
processes do, die cast parts do not have high strength and often have
microfractures and grainflow inconsistencies which 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, but critical applications requiring high strength,
high resistance parts use forgings rather than die castings. Although
the die casting process is not capable of manufacturing high strength,
high resistance parts, die cast parts can reach far greater
complexities with much higher tolerances than any other metal forming
process. In recent years, some traditionally die cast parts which do
not require the strength of metal have been replaced with plastic
injection molded parts due to plastic`s lower cost and lighter weight.