6. Casting is a manufacturing process by which a
liquid material is usually poured into
a mold, which contains a hollow cavity of the
desired shape, and then allowed to solidify.
The solidified part is also known as a
casting, which is ejected or broken out of the mold
to complete the process.
7. Casting materials are usually metals.
Almost all metals can be cast.
Casting is most often used for making complex
shapes that would be otherwise difficult to make
by other methods.
9. Pattern: A pattern is made of wood or metal, is a replica of the final
product and is used for preparing mould cavity
Riser: A column of metal placed in the mold to feed the casting as it
shrinks and solidifies. Also known as a "feed head."
Runner: The channel through which the molten metal is carried from
the sprue to the gate.
Cores: A separated part of the mold, made of sand and generally
baked, which is used to create openings and various shaped cavities in
Gate: A channel through which the molten metal enters the casting
10. Parting Line: Joint where mold separates to permit removal of
the pattern and which shows how and where to open the mold.
Sand: A sand which binds strongly without losing its
permeability to air or gases.
Chaplet: A metal support used to hold a core in place in a mold.
Not used when a core print will serve.
Binders: Materials used to hold molding sand together.
Pouring basin: Filling the mold with molten metal.
Shrinkage: The decrease in volume when molten metal
Mould: The mould contains a cavity whose geometry determines
the shape of cast part.
Mould material should posses refractory characteristics and with
stand the pouring temperature
11. The various casting processes are classified according
to these different moulds
• open mould
• closed mould
12. • Open mould
in which the liquid metal is simply
poured until it fills the open cavity. (fig. a)
the closed mold is provided to permit the
molten metal to flow from outside the mold cavity.
• the closed mold is more important categories in
production casting operation.
15. Casting process divide onto two broad categories
according to types of mold used;
o Expandable mould casting
o Permanent mould casting
16. Expandable mould means that :
the mold in which the molten metal is
solidifies must be break or destroyed to remove the
After solidification of molten metal the mold is break to
remove the desired casting. (sand casting)
Expandable mould materials:
the mold are made out of sand, plaster, and
21. Advantages Disadvantages Recommended
Least Expensive in small
quantities (less than 100)
Ferrous and non -
ferrous metals may be
Possible to cast very
• Least expensive
inferior to other
Surface finish of
usually exceeds 125
finish and low
machining cost does
not warrant a more
23. INVESTMENT CASTING:
Use gravity to fill the mold.
• Mold is destroyed to remove casting
• Metal flow is slow
• Walls are much thicker than in die casting.
• Cycle time is longer than die casting because of inability of mold
material to remove heat.
The investment casting process uses expendable patterns made
of investment casting wax.
25. Advantages Disadvantages Recommended
Complex shape, fine
detail, intricate core
sections and thin walls
Ferrous and non-ferrous
metals may be cast
As-Cast" finish (64 - 125
Costs are higher than
Sand, Permanent Mold
or Plaster process
use of Sand or
The process cost is
savings in machining
27. o In permanent mold casting, the mold is
reused many times.
o The molds are commonly made of steel or
o The Metals commonly cast in the
permanent mold casting include
aluminum, magnesium and copper- based
alloys( brass , bronze)
29. Types permanent mold casting
Two basic two types of permanent
mold casting as under
o Die casting
o Centrifugal casting
30. Die casting:
o Die casting is permanent-mold casting process
in which the molten metal is injected into
mold cavity under high pressure. The pressure
is maintained during solidification, after
which the mold is opened and part is
o Typical pressures are 7 to 350 MPa.
o The molds used in this casting operation is
called dies; hence the name die casting
32. Two types of die casting machines that
o Hot chamber die casting
o Cold chamber die casting
34. o In hot chamber die- casting machines, the molten metal
is poured into a heated chamber from an external melting
container, and piston is used to inject the molten metal
under a high pressure into die cavity.
o Typically injection pressures are 7 to 35 mpa.
o This process only used for the low-melting-point
metals.(zinc,tin ,lead and, sometimes magnesium)
35. o In which the molten metal poured into an
unheated chamber, and piston is used to inject
the liquid metal under a high pressures into the
o Injection pressures used in these machine are
typically 14 to 140 mpa.
36. o In centrifugal casting the mold is rotated at high
speed so that the centrifugal force is produced
that distributes the molten metal to the outer
regions of the cavity.
o Examples of parts made by this process include
pipes, tubes bushing and rings.
39. o High production rates possible.
o Close tolerance is possible for small
o Good surface finish.
o Thin sections are possible.
o Rapid solidification.
40. o Only used for low melting point metals.
o More intricate shapes are not achieved
o Mold is expensive.
Note:(More intricate shapes are not achieved by
the permanent mold casting)
41. For any Metal Casting Process, selection of right
alloy, size, shape, thickness, tolerance, texture, and weight, is very vital.
Views of the Tooling Designer; Foundry / Machine House
needs, customer's exact product requirements, and secondary
operations like painting, must be taken care of before selecting the
appropriate Metal Casting Process.
Economics of machining versus process costs.
Adequate protection / packaging, shipping constraints, regulations of
the final components, weights and shelf life of protective coatings also
play their part in the Metal Casting process.