Casting process

Manufacturing Technology
Megavannan.M
Asst. Professor,
Department of Mechanical Engineering,
QIS college of Engineering Technology,
Ongole, Andrapradesh.

 ‘Manufacturing’ is derived from the Latin,
manus = hand and factus = made,
that is, the literal meaning is “made by hand”.
‘Manufacturing’ means the making of goods and articles by
hand and/or by machinery.
 ‘Manufacturing Technology’ or “Production Technology”
can be defined as the study of the various processes
required to produce parts and to assemble them into
machines and mechanisms.

CLASSIFICATION OF MANUFACTURING PROCESSES
 (Metal) Casting Processes
 Joining Processes
 (Metal) Forming Processes
 Sheet metal Processes
 Plastic materials (Polymers) processes
 Machining processes
 Powder Metallurgy
 Heat treatment & Surface treatment processes
 Assembly processes

INTRODUCTION
 FERROUS METALS
 Ferrous Metals mostly contain Iron. They have small amounts of
other metals or elements added, to give the required properties
 Examples are,
 cast iron,
 mild steel,
 medium carbon steel,
 high carbon steel,
 stainless steel and
 high speed steel.
 Aluminium
Some of the complicated shapes may not be produced on the components with
conventional machining processes.

Non-Ferrous metals
Non-Ferrous Metals do not contain Iron, are
not magnetic and are usually more resistant to
corrosion than ferrous metals.
Some examples are:
– Aluminium & Aluminium Alloys.
– Copper.

CASTING PROCESS
 Casting is one of the processes used for making
components of complicated shapes in larger
quantity.
 Producing metal parts by pouring molten metal into
the mould or mold cavity of the required shape and
allowing the metal to solidify.
 The solidified metal piece is called as “casting”
 A plant where the castings are made is called a
“Foundry”

Steps involved in casting process

Methodology involved in Casting process

Pattern
Primarily used to produce the mould cavity in
sand.
It is slightly larger than the desired casting,
due to various allowances.

TYPES OF PATTERN
 Solid or Single piece pattern
 Split pattern
 Loose piece pattern
 Match plate pattern
 Gated pattern
 Sweep pattern
 Skeleton pattern
 Segmental pattern
 Multi piece pattern
 Cope or drag pattern

Solid Or Single Piece Pattern
Simplest pattern
Made in one piece
Cheapest pattern
Application
Soil tamper
Stuffing box
Gland of steam engines

Split Pattern
 Pattern is split into two pieces.
 One part is in cope and another part is drag.
 Easy withdrawal of a pattern.
Application
A. Spindles
B. Steam valves
C. Ak-47 rifle stock

Multi Piece Pattern
a. Pattern is split into more than two
pieces.
b. Facilitates on easy moulding and
withdrawal of pattern.
c. Pattern may consist of 3,4 or more
numbers depending on patterns.
Application
 Lap Joint
 Dowel Joint
 Mitre Joint

Loose Piece Pattern
 Pattern consist of loose pieces for easy
withdrawal.
 These loose pieces form integral part of
pattern during moulding.
 After mould is complete pattern is
withdrawn leaving the loose pieces.
Applications
Rotor hub
Axle pin
Handling parts

Pattern Materials
1. Wood – Teak, Mahogany, White pine….
2. Metal – Cast Iron, Brass, Aluminium, White metal……
3. Plaster
4. Plastics
5. Wax

COLOUR SCHEME FOR PATTERNS
1. Surface as cast : BLACK
2. Machined surface : RED
3. Core prints an seats : YELLOW
4. Loose pieces : YELLOW / RED
(diagonal stripes)
5. Stop-off : YELLOW / BLACK
(diagonal stripes)

SELECTION OF PATTERN MATERIALS
(Requirements of a good pattern)
 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.

Pattern Allowance
The difference in the dimensions of the casting
and the pattern is due to the various allowances
considered while designing a pattern for a casting.
The various types of allowances are,

MOULDING SAND
Special type of sand is used for making mould.
 3 Essential constituents
1. Refractory sand
2. Binder
3. Additive
Silica is widely used as moulding sand.
It has 80 to 90 % - Silica Dioxide
It gives refractoriness to the sand.

Types of Sand
1. Natural Sand
 Available from natural deposits
 Needs only 5-8% water
 Used for light castings in Ferrous & Non-Ferrous
2. Synthetic Sand
 Prepared (with desired properties, as we like) artificially by
mixing clay free sand
 Used in mechanized production machine moulding & High
pressure moulding.
3. Special Sand
a) Zircon sand
b) Chromite sand

Types of Moulding Sand
1. GREEN SAND
- in moist state
- 5 to 8 % of water & 16 to 30 % of clay
- Having good damping capacity
- Small and medium size castings
2. DRY SAND
- in dry stage
- called as ‘dry sand mould’ or ‘skin dry mould’
- large castings

3. Facing Sand
4. Loam Sand
 Consists of fine silica sand, fine refractories, clay (arround
50 %), graphite, fibre and water.
 Melting large castings – Bell, Roller, Pulleys etc.,
5. Backing Sand
Used to backup the facing sand and to fill the whole volume
of the mould box.
Old sand may used repeatedly
6. Parting Sand

Properties of Moulding Sand
 Porosity or Permeability
 Plasticity or Flow ability
 Strength or Cohesiveness
 Refractoriness
 Adhesiveness
 Collapsibility

Desirable Mold sand Properties and
Characteristics
 Strength - to maintain shape and resist erosion
 Permeability - to allow hot air and gases to pass through
voids in sand
 Thermal stability - to resist cracking on contact with molten
metal
 Collapsibility - ability to give way and allow casting to shrink
without cracking the casting
 Reusability - can sand from broken mold be reused to make
other molds.

BINDERS
 Organic - Cereal, resins, pitch, drying oil, molasses etc.,
 In-Organic - Fire clay, KAOLINITE, BENTONITE
 High Thermo Chemical stability
TYPICAL GREEN MOULDING SAND for gray iron
Silica sand = 68 to 86%
Clay = 10 to 20%
Water = 3 to 6%
Additives = 1 to 6%

Additives
Additives are added to the molding sand to
improve the properties like strength, refractoriness and
permeability.
Necessary of Additives:
1. To give a good surface finish to the casting
2. To eliminate casting defects
(Expansion of moulding sand or Contraction of he casting)

1) Sea Coal – fine bituminous coal powder
2) Saw dust
3) Pitch – distilled from soft coal
4) Cereals – ground corn flour or corn starch
5) Silica flour – very fine powdered silica
6) Special additives
Fuel oil
Dextrin
Molasses
Iron oxide

Transport :
Automobile, aerospace, railways and shipping
Heavy Equipment :
Construction, farming and mining
Machine Tools :
Machining, casting, plastics molding, forging, extrusion and forming
Plant Machinery :
Chemical, petroleum, paper, sugar, textile, steel and thermal plants
Defense :
Vehicles, artillery, munitions, storage and supporting equipment
Applications of casting process

Applications of casting process
• Electrical Equipment Machines :
– Motors, generators, pumps and compressors
• Hardware :
– Plumbing industry pipes, joints, valves and fittings
• Household :
– Appliances, kitchen and gardening equipment, furniture and
fittings
• Art Objects :
– Sculptures, idols, furniture, lamp stands and decorative items

Casting process

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