ME1008: MANUFACTURING
TECHNOLOGY
UNIT I
CASTING
INTRODUCTION TO CASTING

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.

It is most ancient process of manufacturing
metallic components.
INTRODUCTION TO CASTING
Following steps involved in the casting process
 Melting the metal.
 Pouring it into a previously made mould or
cavity.
 Cavity which conforms the shape of the desired
component which we obtained.
 Allowing the molted metal to cool and solidify
in the mould.
 Removing the solidified component from the
mould.
 Cleaning it for further treatment if necessary.
Note: “the solidified piece of metal which is taken out of
mould is casting”
APPLICATIONS

Engine and cylinder block.
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Pistons, piston rings
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Wheels and housing of steam and hydraulic
turbines.
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Turbine and jet engine blades, etc.
CLASSIFICATION OF CASTING
PROCESS

Expandable mould casting, one casting mould with
less accuracy, eg: sand casting.
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Permanent mould casting, mould will used
repeatedly for number of casting be achieved, it is
used for mass production and it with high
accuracey.
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Semi-permanent casting, high refractory materials
is used, so it is not suitable for permanent moulding.
PATTERNS
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In casting, a pattern is a replica of the object to
be cast, used to prepare the cavity into which
molten material will be poured during the
casting process.
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It is not exact replica of the exact desired
casting.
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It is slightly larger than the desired casting,
because of allowances.
TYPES OF PATTERN
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Single piece pattern
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Split piece pattern
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Loose piece, Gated, match pattern
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Sweep pattern
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Cope and drag pattern
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Skeleton pattern
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Shell and follow board pattern.
TYPES OF PATTERN contd….
Single piece pattern: It is simplest of all pattern
is made in one piece. It is suited for limited
process only.
Spilt piece pattern: It is used for intricate casting
for usual shapes. These two patterns are joined
together with the help of dowel pins.
TYPES OF PATTERN contd….
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Loose piece pattern: Some patterns usually
single piece are made to have loose pieces in
order to enable their easy with drawn from the
mould.
TYPES OF PATTERN contd….
Gate pattern
Match plate pattern
TYPES OF PATTERN contd….
Sweep pattern
Cope and drag
TYPES OF PATTERN contd….
Skeleton pattern
Follow
pattern
TYPES OF PATTERN contd….
Shell pattern
REQUIREMENTS OF A GOOD
PATTERN
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Secure the desired shape and size of the casting.
Cheap and readily repairable.
Simple in design for ease of manufacture.
Light in mass and convenient to handle.
Have high strength and long life in order to
make as many moulds as required.
Retain its dimensions and rigidity during the
definite service life.
Its surface should be smooth and wear resistant.
Able to withstand rough handling.
DESIGN CONSIDERATION IN
PATTERNS
1.
Proper allowance should be provided.
2. The parting line should be carefully selected.
3. Proper material should always be selected.
4. The wall thickness and sections should kept as
uniform as possible. Abrupt changes should invariably
be avoided.
5. The use of offset pairing, instead of cores, should be
encouraged to as great extent as it is possible. Abrupt
changes should invariably be avoided.
PATTERN LAYOUT
Pattern making consists of two different stages to prepare
a layout and to shape the different parts. Layout consists
of the following steps:
a. Initially study the drawing pattern and select a wood
that can suitably accommodate two views.
b. Take on surface of the wood as base and plane the
adjacent surface.
c. Take a folding rule and measure the dimensions as per
the drawing.
d. Prepare the layout by using various measuring and
marking tools locating position of core prints and surface
to be machined.
PATTERN MATERIALS

Wood: Piece and short run production
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Metal: Large scale and mass production
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Cement, Plastics for example epoxy resin: Batch
production.
ALLOWANCE
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Shrinkage allowance
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Machining allowance

Pattern draft or tapper
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Corners and fillets
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Rapping or shake allowance
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Distortion allowance
MOULDING SAND

Molding sand is also known as foundry sand.

Sand with moistened and compressed to pack
well and hold its shape.

It is used in the process of sand casting.

Green sand is an aggregate of sand, bentonite
clay, pulverized coal and water.

Main purpose of this sand to make mould cavity
for casting process.
MOULDING SAND contd…
Green sand:
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It is sand used in the wet condition for making
the mould. It is mixture of silica sand with 15-25
per cent clay and 6-8 per cent water

Green sand moulds are not dried and metal is
poured in them in the wet condition
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Being damp the sand can be easily worked with
hand to give it any desired shape

This sand is used for producing small to medium
sized moulds which are not very complex
MOULDING SAND contd…
Loam sanding:

Loam sand is sand containing up to 50 % clay
which has been worked to the consistency of
builder mortar.

This sand is used for loam sand moulds for
making very heavy castings usually with the
help of sweeps and skeleton patterns.
MOULDING SAND contd…
Dry sand:
If we dry the green sand mentioned above, then we get dry sand.
the physical composition remains same, except for water
content.
Facing sand:
This sand comes in contact with direct contact of molten metal
hence it is subjected to severest conditions. the basic
composition is silica sand and clay.
GATING AND RISERING
The assembly of channels which facilitates the molten metal to
enter into the mold cavity is called the gating system.
 Gating also called as sprue.
Goals of Gating System:
The goals for the gating system are:
 To minimize turbulence to avoid trapping gasses into the mold
 To get enough metal into the mold cavity before the metal starts
to solidify
 To avoid shrinkage
 Establish the best possible temperature gradient in the
solidifying casting so that the shrinkage if occurs must be in the
gating system not in the required cast part.
 Incorporates a system for trapping the non-metallic inclusions
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CORE

A core is a device used in casting and molding
processes to produce internal cavities and
reentrant angles.

The core is normally a disposable item that is
destroyed to get it out of the piece.

They are most commonly used in sand casting,
and also used in injection molding method.
SHELL MOULD CASTING
• Shell mold casting is a metal casting process
similar to sand casting.
• Molten metal is poured in mold cavity.
• In shell mold casting, the mold is a thinwalled shell created from applying a sand-
resin mixture around a pattern.
SHELL MOULD CASTING contd….
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Metal piece pattern is used, so it reused to make
more number of mould.
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It allows the higher production rate.
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Shell mold casting allows the use of both ferrous
and non-ferrous metals, most commonly cast
iron, carbon steel, alloy steel, stainless steel,
aluminum alloys, and copper alloys used.
SHELL MOULD CASTING contd….
The shell mold casting process consists of
the following steps:
 Pattern
creation: A two-piece metal pattern is
created in the shape of the desired part, typically
from iron or steel.
Other materials such as aluminum for low
volume production or graphite for casting
reactive materials.
SHELL MOULD CASTING contd….
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Mold creation - First pattern is heated to 175-370°C
(350-700°F) and coated with a lubricant to facilitate
removal.
Next, the heated pattern is clamped to a dump box
contains a mixture of sand and a resin binder.
The dump box is inverted, allowing this sand-resin
mixture to coat the pattern.
The heated pattern partially cures the mixture,
which now forms a shell around the pattern.
Each pattern half and surrounding shell is cured to
completion in an oven and then the shell is ejected
from the pattern.
SHELL MOULD CASTING contd….
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Mold assembly - The two shell halves are joined
together and securely clamped to form the
complete shell mold.

If any cores are required they are inserted prior
to closing the mold. The shell mold is then
placed into a flask and supported by a backing
material.
SHELL MOULD CASTING contd….
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Pouring - The mold is securely clamped
together while the molten metal is poured from a
ladle into the gating system and fills the mold
cavity.
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Cooling - After the mold has been filled, the
molten metal is allowed to cool and solidify into
the shape of the final casting.
SHELL MOULD CASTING contd….
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Casting removal - After the molten metal has
cooled, the mold can be broken and the casting
removed.
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Trimming and cleaning processes are required to
remove any excess metal and sand from the feed
system.
INVESTMENT CASTING
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Investment casting is an industrial process based
on and also called lost-wax casting.
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The first step in investment casting is to
manufacture the wax pattern for the process.
INVESTMENT CASTING contd….
INVESTMENT CASTING contd….
INVESTMENT CASTING contd….
INVESTMENT CASTING contd….
INVESTMENT CASTING contd….
INVESTMENT CASTING contd….
CENTRIFUGAL CASTING
CENTRIFUGAL CASTING
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In this process molten metal is poured into a
spinning die.
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The die can be spinning either on a vertical or
horizontal axis depending on the configuration
of the desired part.

Ring and cylinder types cast vertical centrifugal
process.

Tubular shapes are made with the horizontal
centrifugal process.
CENTRIFUGAL CASTING contd….
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Permanent mold is rotated continuously about
its axis at high speeds (300 to 3000 rpm) as the
molten metal is poured.

The molten metal is centrifugally thrown
towards the inside mold wall, where it solidifies
after cooling.
CENTRIFUGAL CASTING contd….
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Castings can be made in almost any length,
thickness and diameter.
Different wall thicknesses can be produced from
the same size mold.
Eliminates the need for cores.
Resistant to atmospheric corrosion, a typical
situation with pipes.
Mechanical properties of centrifugal castings are
excellent.
Only cylindrical shapes can be produced with
this process.
CENTRIFUGAL CASTING contd….
Features of centrifugal casting:
 Castings can be made in almost any length,
thickness and diameter.
 Different wall thicknesses can be produced from
the same size mold.
 Eliminates the need for cores.
 Resistant to atmospheric corrosion, a typical
situation with pipes.
 Mechanical properties of centrifugal castings are
excellent.
 Only cylindrical shapes can be produced with
this process.
DEFECTS IN CASTING
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Open Blows and Blow Holes
Pin Hole Porosity
Entrapped Air and other gases
Cracked Casting
Bent or Twisted Casting
Dropped Mould
Fusion
Swell
Run out
Mismatch
Mis-run and Cold Shut