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Casting
1.
2. CASTING
Casting is a manufacturing process where a solid is melted,
heated to proper temperature (sometimes treated to
modify its chemical composition), and is then poured into
a cavity or mold, which contains it in the proper shape
during solidification.
Thus, in a single step, simple or complex shapes can be
made from any metal that can be melted. The resulting
product can have virtually any configuration the designer
desires
The solidified part is also known as a casting, which is
ejected or broken out of the mold to complete the process.
3.
4. TERMINOLOGY
Metal casting processes uses the following terminology:
Pattern: An approximate duplicate of the final casting
used to form the mold cavity.
Molding material: The material that is packed around
the pattern and then the pattern is removed to leave
the cavity where the casting material will be poured.
Flask: The rigid wood or metal frame that holds the
molding material.
Cope: The top half of the pattern, flask, mold, or core.
Drag: The bottom half of the pattern, flask, mold, or
core.
5.
6. Core: An insert in the mold that produces internal features in the casting, such as holes.
Core print: The region added to the pattern, core, or mold used to locate and
support the core.
Mold cavity: The combined open area of the molding material and core, where the
metal is poured to produce the casting.
Gating system: The network of connected channels that deliver the molten
material to the mold cavities.
Pouring cup or pouring basin: The part of the gating system that
receives the molten material from the pouring vessel.
Sprue: The pouring cup attaches to the sprue, which is the vertical part of the gating
system. The other end of the sprue attaches to the runners.
Runners: The horizontal portion of the gating system that connects the sprues to the
gates.
Gates: The controlled entrances from the runners into the mold cavities.
Riser: An extra void in the mold that fills with molten material to compensate for
shrinkage during solidification.
7. Vents: Additional channels that provide an escape for
gases generated during the pour.
Parting line or Parting surface: The interface
between the cope and drag halves of the mold, flask,
or pattern.
Draft: The taper on the casting or pattern that allow it
to be withdrawn from the mold
Core box: The mold or die used to produce the cores.
8. CASTING PROCESS
The metal casting process has been divided into the
following five major operations:
Obtaining the Casting Geometry :
The process is referred as the study of the geometry of
parts and plans, so as to improve the life and quality of
casting.
9. Casting Patternmaking :
In pattern making, a physical model of casting, i.e. a
pattern is used to make the mold.
The mold is made by packing some readily formed
aggregated materials, like molding sand, around the
pattern. After the pattern is withdrawn, its imprint
leaves the mold cavity that is ultimately filled with
metal to become the casting.
10. Coremaking & Molding :
In core making, cores are formed, (usually of sand) that
are placed into a mold cavity to form the interior
surface of the casting. Thus the annul space between
the mold-cavity surface and the core is what finally
becomes the casting.
Molding is a process that consists of different operations
essential to develop a mold for receiving molten metal.
11.
12. Alloy Melting and Pouring :
Melting is a process of preparing the molten material
for casting. It is generally done in a specifically
designated part of foundry, and the molten metal is
transported to the pouring area wherein the molds are
filled.
13. Casting Cleaning:
Cleaning is a process that refers to the different
activities performed for the removal of sand, scale, and
excess metal from the casting.
However, all the operations may not apply to each
casting method but such processes play an important
role to comply with environmental guidelines.
14. ADVANTAGES OF
CASTING
Casting process enjoys certain advantages :
Owing to physical properties, some metals can only be cast since they
cannot be re-modelled into bars, rods, plates or other shapes.
It's a process highly adaptable to the requirements of mass production.
Large numbers of a given casting can be produced quickly. For
example; in the automotive industry there is massive production of cast
engine blocks and transmission cases.
Certain light metal alloys because of their respective strength and
weakness, can be produced only as castings.
Shows excellent bearing qualities.