Sand casting and die casting have some similarities, yet they
are worlds apart when it comes to their production. Both
processes are methods for producing castings out of various
types of metals. Sand castings can be produced from a variety of
metals, but the most popular metals are aluminum, grey iron,
ductile iron, steel, and magnesium. Die casting mostly feature
non-ferrous metals such as zinc, copper, aluminum, magnesium,
lead, tin, etc. Both methods of casting use a pattern or mold to
create the cavity, and molten metal is used to fill the cavity
creating the desired part. That is where the similarities
between the two methods end.
In the sand casting process a pattern, or mold, is needed to
create the empty cavity within the sand to create the shape of
the desired part. This means that the pattern could be made out
of a variety of materials, such as wood, metal, polyurethane
board, or even plastic. The material the pattern is made from
depends on how many castings it is needed to produce. The
pattern then becomes part of a core box which is necessary for
final production. A core box (pictured above) is just that, a
box that the pattern is placed in, filled with sand, and then
packed to form the shape of the pattern. The sand, which is
chemically bonded to hold its shape, is then removed and can be
filled with molten metal.
Die casting also requires a pattern, or mold, to produce the
metal casting, except these patterns require much more. The
process of die casting involves forcing molten metal metals into
a mold under high pressures. Unlike sand casting, the molten
metal will be in direct contact with the mold during the die
casting process. This means that the pattern/mold must be able
to withstand immense pressures and extreme heat repeatedly.
Typically, the mold is created out of hardened steel as it can
withstand the heat and pressure associated with die casting.
The equipment needed for die casting combined with the costs to
produce patterns/molds out of hardened steel make up the large
capital costs associated with die casting. Due to the high
costs, die casting tends to be reserved for high volume
production runs as it would just not be cost effective for
smaller quantities. Also, die casting is a good method of
limiting and/or eliminating porosity issues since the metal is
forced into the die under high pressure. Sand casting is much
more cost effective at smaller quantities due to the resources
and equipment needed to produce them. The pattern can be created
out of a variety of materials and the sand used in the casting
process can be reused further helping reduce costs. Each method
of casting is capable of producing high quality castings, but
each method has its own positives and negatives that one must
weigh when considering the two. Here at our Industry, we
specialize on prototype and low quantity production castings
making sand casting our preferred method of casting.
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