The Die Casting Process[pP]>key no cd pes 5
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The Die Casting Process
uses two
permanent mold halves of a die, mounted in a press and brought
together. Molten metal is injected into the die through a runner and
gate with pressures in the area of 2000-5000 psi. Air escapes
into overflow wells, and out vents, as metal fills the molds. The mold
is chilled, and the injected metal freezes. the mold is
separated, and knockout pins eject the part
(see diagram below).
Cycle times are typically given in seconds.
The parts are cut off the runners and sprues.[pP]>key no cd pes 5
The
Metals used
in die casting are low melting point, non-ferrous metals. Most die
casting is done using aluminum and zinc, with smaller, but growing, industries
in magnesium, copper, lead and tin.[pP]>key no cd pes 5
The
Dies
are typically made of carbon steel or special alloys and must withstand high
pressures and extreme temperature fluctuations. Dies may incorporate multiple
cavities to
lower part cost, which is proportional to machine time and materials. Dies often
require water lines to enhance cooling and decrease cycle time..
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1) Molten Metal
is ready for injecting and the die halves are pressed together[pP]>key no cd pes 5
[pP]>key no cd pes 5
2) Molten Metal
is injected into the die[pP]>key no cd pes 5
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3) The die halves
are separated[pP]>key no cd pes 5
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4) Knockout pins
eject the part[pP]>key no cd pes 5
Advantages
of Die Casting: Although the
initial tooling cost is high, die cast parts are produced in short cycles and
thus have a low unit cost. Die castings parts are created under high pressure,
allowing for thinner wall sections, better surface finish, more intricate
geometry and tighter tolerances. These advantage provides the benefit of a cast
to net shape or nearly net shape, thus cutting down on the cost of the secondary
machining and finishing operations. Also, inserts are feasible.[pP]>key no cd pes 5
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Using modern die casting technology, Twin City Die
Castings was able to meet the flatness and parallelism requirements
directly out of the cast machine. Secondary machining was limited to
tapping two holes. All this reduced part price to $3 a copy, and the
customer regained the $20,000 cost of the die cast tooling before the
350th part had been produced.[pP]>key no cd pes 5
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Last modified February 24, 2008[pP]>key no cd pes 5
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Case
Study: Although die casting is most often used for large production
runs, in many instances the savings in part price is enough to justify the
tooling costs even at relatively low yearly quantities. The connector part shown
at right was designed by a major computer manufacturer. Since the yearly
requirement was only 750 pieces, the computer manufacturer had used a lost wax
investment casting process. The tolerance requirements for the part, however,
included one parallelism and three flatness specifications. With all the
secondary machining required to meet those specs, part price was $65.[pP]>key no cd pes 5