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What is Casting?

• Casting is a process in which molten metal flows by

gravity or other force into a mold where it solidifies in theshape of the mold cavity

• The term casting   also applies to the part made in the

process

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Overview of Casting Technology

• Mold contains cavity whose geometry determines partshape

•  Actual size of cavity must be slightly oversized to allow

for shrinage of metal during solidification and cooling!

• Molds are made of a variety of materials" including

sand" plaster" ceramic and metal

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open mold" simply a

container in the

shape of the desired

part

Closed mold" in which the

mold geometry is more

comple# and re$uires a gating

system %passageway& leading

into the cavity

Two Types of Molds

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Two Types of Casting 'rocess

1. Expendable mold process− uses an expendable mold   which must be

destroyed to remove casting

− Mold materials( sand" plaster" and similar

materials" plus binders!

2. Permanent mold process

− uses a permanent mold  which is reusable

− generally made of metal %or" less commonly" aceramic refractory material&

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 Advantages and )isadvantages

• More intricate%complicated& geometries are possible

with e#pendable mold processes!

• 'ermanent mold processes are more economic in high

production operations!

Two Types of Casting 'rocess *

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Casting Terms

• Flask:  A moulding flas is one which holds the sand mould

intact! +t is made up of wood  for temporary applications ormetal for long,term use! 

• Drag: -ower moulding flas! 

• Cope: .pper moulding flas!

• Cheek: 

+ntermediate moulding flas used in three,piecemoulding!

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• Pattern: 'attern is a replica of the final ob/ect to be made with

some modifications! When the pattern is removed" theremaining cavity has desired shape of final part! The pattern is

usually oversized to allow for shrinage of metal as it solidifies

and cools!

• Parting line:  This is the dividing line between the two

moulding flass that mae up the sand mould! In splitpattern it is also the dividing line between the two

halves of the pattern.

Casting Terms *

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• Backing sand( +t constitutes most of the refractory material

found in the mould! This is made up of used and burnt sand!• Core:  .sed for maing hollow cavities in castings! +n sand

casting" cores are generally made of sand!

● Pouring basin (cup):  A small funnel,shape at the top of the

mould into which the molten metal is poured! +t  minimizessplash and turbulence as the metal flows into down sprue!

• Sprue: The passage through which the molten metal reaches

the mould cavity! In many cases it controls the ow ofmetal into the mould.

Casting Terms *

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• Runner : The passage way in the parting plane through which

molten metal flow is regulated before it reaches the mould

cavity! 

• Gate:  The actual entry point through which molten metal

enters the mold cavity in a controlled rate!

•  Chaplet: 

Chaplets are used to support cores insidethe mould cavity and overcome the metallostaticforces. 

• Chill:  Chills are metallic ob/ects" which are placed in the 

mould at some places to increase the cooling rate of castings!

Casting Terms *

•   Riser: 

It is a reservoir of molten

metal to compensate for

shrinkage during solidification.

The riser must be designed to

freeze after the main casting in

order to satisfy its function.

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0teps in Casting

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Capabilities and Advantages of Casting

−Can create comple# part geometries

−Can create both e#ternal and internal shapes

−0ome casting processes are net shape; others are

near net shape−Can produce very large parts

−0ome casting methods are suited to mass production

− All varieties of metals can be cast %ferrous and

nonferrous&

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)isadvantages of Casting

−-imitations on mechanical properties

−'oor dimensional accuracy and surface finish with

some processes! e!g!" sand casting

−0afety hazards to worers due to hot molten metals

−1nvironmental problems

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Casting , Applications

• 2ig parts(  engine blocs and heads for automotive

vehicles" wood burning stoves" machine frames" railway

wheels" pipes" church bells" big statues" and pump

housings

• 0mall parts(  dental crowns" /ewelry" small statues" and

frying pans