Annexure-I
4.2 Moulding and casting
Process of making cavity is called Moulding. And pouring the molten
metal to produce desired shape is called Casting.
The cavity in the sand is formed by using a pattern (an approximate
duplicate of the real part), which are typically made out of wood,
sometimes metal
Most versatile form of production processes
There is no limit to the size and shape of the components
Production cost is considerably low
All metals can be cast
Green Sand Casting- steps
Pattern
Ramming process
Molten box
Vent holes making
Pattern into the box
Pattern into the sand
Applying parting powder
Rapping the Pattern
Cutting the Funnel Around
the Sprue Pin
Cutting the Gates
Cutting the Funnel
Around the Sprue Pin
Melting Metal
Pouring Metal in to mould
cavity
Green SAND
MOLD
FEATURES
Destroy the sand
Final Casting Product
Pattern:
A Pattern is a model or the replica of the
object to be cast.
Patterns may be in two or three pieces,
where as casting are in a single piece.
A pattern is required even if one object has
to be cast.
The quality of casting and the final product
will be effected to a great extent by the
planning of pattern.
Functions of Patterns:
 A Pattern prepares a mould cavity for the
purpose of making a casting.
 A Pattern may contain projections known as
core prints if the casting requires a core and
need to be made hollow.
 Risers, runners and gates may form a part of
the pattern.
 Patterns properly made and having finished
and smooth surfaces reduce casting defects.
 Properly constructed patterns minimize
overall cost of the casting.
Selection of Pattern Materials:
The following factors assist in selecting proper pattern material:
No. of castings to be produced.
Metal to be cast.
Dimensional accuracy & surface finish.
Shape, complexity and size of casting.
Casting design parameters.
Type of molding materials.
The chance of repeat orders.
Nature of molding process.
Position of core print.
The pattern material should be:
1.
2.
3.
4.
5.
Easily worked, shaped and joined.
Light in weight.
Strong, hard and durable.
Resistant to wear and abrasion .
Resistant to corrosion, and to chemical
reactions.
6. Dimensionally stable and unaffected by
variations in temperature and humidity.
7. Available at low cost.
Materials for making patterns:
a.
b.
c.
d.
e.
Wood
Metal
Plastic
Plaster
Wax.
Types of patterns depend upon the following
factors:
i. The shape and size of casting
ii. No. of castings required
iii. Method of moulding employed
iv. Anticipated difficulty of moulding
operation
Types of Patterns:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Single piece pattern.
Split piece pattern.
Loose piece pattern.
Match plate pattern.
Sweep pattern.
Gated pattern.
Skeleton pattern
Follow board pattern.
Cope and Drag pattern.
1. Single piece (solid) pattern:
• Made from one piece and does not contain loose
pieces or joints.
• Inexpensive and used for large size simple
castings.
• Pattern is accommodated either in the cope or in
the drag.
Examples:
Bodies of regular shapes.
Stuffling box of steam engine.
2. Split piece pattern:
• Patterns of intricate shaped castings cannot be made in
one piece because of the inherent difficulties associated
with the molding operations (e.g. withdrawing pattern
from mould).
• The upper and the lower parts of the split piece patterns
are accommodated in the cope and drag portions of the
mold respectively.
• Parting line of the pattern forms the parting line of the
mould.
• Dowel pins are used for keeping the alignment between
the two parts of the pattern.
• Examples:
1. Hallow cylinder
2. Taps and water
stop cocks etc.,
3.Loose piece pattern:
• Certain patterns cannot be withdrawn once
they are embedded in the molding sand. Such
patterns are usually made with one or more
loose pieces for facilitating from the molding
box and are known as loose piece patterns.
• Loose parts or pieces remain attached with
the main body of the pattern, with the help of
dowel pins.
• The main body of the pattern is drawn first
from the molding box and thereafter as soon
as the loose parts are removed, the result is
the mold cavity.
4. Match plate pattern:
• It consists of a match plate, on either side of
which each half of split patterns is fastened.
• A no. of different sized and shaped patterns may
be mounted on one match plate.
• The match plate with the help of locator holes
can be clamped with the drag.
• After the cope and drag have been rammed with
the molding sand, the match plate pattern is
removed from in between the cope and drag.
• Match plate patterns are normally used in
machine molding.
• By using this we can eliminate mismatch of cope
and drag cavities.
Fig: Match plate pattern
5. Sweep pattern:
• A sweep pattern is just a form made on a wooden
board which sweeps the shape of the casting into
the sand all around the circumference. The sweep
pattern rotates about the post.
• Once the mold is ready, Sweep pattern and the post
can be removed.
• Sweep pattern avoids the necessity of making a full,
large circular and costly three-dimensional pattern.
• Making a sweep pattern saves a lot of time and
labour as compared to making a full pattern.
• A sweep pattern is preferred for producing large
casting of circular sections and symmetrical shapes.
6. Gated pattern:
• The sections connecting different patterns
serve as runner and gates.
• This facilitates filling of the mould with molten
metal in a better manner and at the same time
eliminates the time and labour otherwise
consumed in cutting runners and gates.
• A gated pattern can manufacture many casting
at one time and thus it is used in mass
production systems.
• Gated patterns are employed for producing
small castings.
castings
Gating system
7. Skeleton pattern:
• A skeleton pattern is the skeleton of a desired
shape which may be S-bend pipe or a chute or
something else. The skeleton frame is mounted
on a metal base
• The skeleton is made from wooden strips, and is
thus a wooden work.
• The skeleton pattern is filled with sand and is
rammed.
• A strickle (board) assists in giving the desired
shape to the sand and removes extra sand.
• Skeleton patterns are employed for producing a
few large castings.
• A skeleton pattern is very economical, because it
involves less material costs.
8. Follow board pattern:
• A follow board is a wooden board and is used for
supporting a pattern which is very thin and
fragile and which may give way and collapse
under pressure when the sand above the
pattern is being rammed.
• With the follow board support under the weak
pattern, the drag is rammed, and then the fallow
board is with drawn, The rammed drag is
inverted, cope is mounted on it and rammed.
• During this operation pattern remains over the
inverted drag and get support from the rammed
sand of the drag under it.
• Follow boards are also used for casting master
patterns for many applications.
9. Cope and Drag patterns:
• A cope and drag pattern is another form of split
pattern.
• Each half of the pattern is fixed to a separate
metal/wood plate.
• Each half of the pattern(along the plate) is molded
separately in a separate molding box by an
independent molder or moulders.
• The two moulds of each half of the pattern are finally
assembled and the mould is ready for pouring.
• Cope and drag patterns are used for producing big
castings which as a whole cannot be conveniently
handled by one moulder alone.
Fig: Cope and drag pattern
Properties of moulding sand
Refractoriness : It is the ability of the moulding sand to with stand the high temperature of
molten metal.
Strength: The moulding sand should have sufficient strength to retain mould.
Flowability: Flowability is the ability of the moulding sand to get compacted to take up the
required shape
Permeability: the moulding sand should be porous enough to allow the gases picked up by
the molten metal while transferring or gases generated in the mould to escape from
mould
Cohesiveness: It is ability of the moulding sand grains to adhere to each other.
Adhesiveness: Adhesiveness is the property of moulding sand to adhere to the walls of
moulding boxes
Collapsibility: Collapsibility is the readiness of the moulding sand to get collapsed after the
solidification of the casting
Durability: It is ability of the moulding sand to with stand the heating and coolong during
repeated usage.
Melting furnaces - Cupola and Electric Furnace
Cupola
Furnace
 Charge – the metal and fuel put into the furnace. A
charge is made up of coke, iron, and limestone.
 Stack – where the charges sit until they reach the melt
zone.
 Melt Zone- the area in the furnace where the cold iron
melts.
 Cast iron melts at about 2,700 degrees Fahrenheit.
 Well – where the molten iron pools until the furnace is
ready to be tapped.
 Wind Belt – distributes air evenly from blower to all
tuyeres.
 Tuyeres - openings in the furnace that allow blast air to
enter furnace
ELECTRIC ARC FURNACE
• Various are available which can carry from 1
ton to 400 ton of melting works
• The rod penetrated in furnace can be 2 or 3
• The roof can be fixed or tilting with the
furnace
CONSTRUCTION
• An electric arc furnace used for steelmaking consists of a refractory-lined
vessel, usually water-cooled in larger sizes, covered with a retractable roof,
and through which one or more graphite electrodes enter the furnace.
The furnace is primarily split into three sections:
• the shell, which consists of the sidewalls and lower steel 'bowl';
• the hearth, which consists of the refractory that lines the lower bowl;
• the roof, which may be refractory-lined or water-cooled, and can be
shaped as a section of a sphere, or as a frustum (conical section). The roof
also supports the refractory delta in its centre, through which one or more
graphite electrodes enter.
Electric Arc Furnace
• A current is passed from separate electrodes
creating arcs of ionized gas
• Heat is transferred from the arc into the
charge material
• Can be either DC or AC
Resistance Furnace
• A current passed through a material resulting
in ohmic heating
• Radiation heats charge material
• Some convection and conduction occurs
Mind Map
(Annexure II)
Mind Map
(Annexure II)
Copola Furnace
Working Principle
Electric Arc Furnace
Constructions
Induction Furnace
Advantages
Resistance Furnace
Dis advantages
Oxygen fuel Furnace
Summary
•
Annexure III
Casting is a process in which molten metal flows into a mold where it solidifies in
the shape of the mold cavity. The part produced is also called casting.
•
A Pattern is a model or the replica of the object to be cast.
•
Risers, runners and gates may form a part of the pattern.
•
The following factors assist in selecting proper pattern material
•
Metal to be cast, accuracy & surface finish, Shape, complexity and size of casting,
Casting design parameters, Type of molding materials, The chance of repeat
orders, Nature of molding process, Position of core print.
•
Materials for making patterns: Wood, Metal, Plastic, Plaster and Wax.
•
Types of Patterns: Single piece pattern. Split piece pattern. Loose piece pattern.
Match plate pattern. Sweep pattern. Gated pattern. Skeleton pattern, Follow board
pattern. Cope and Drag pattern.
•
Advantages and applications are discussed
Summary
Annexure III
• Furnace is used to melt the workspace to be casted.
• Types of Furnace
– Cupola
– Electric Arc
– Induction
– Oxy-fuel
– Resistance
• All the furnace construction and working principle are discussed.
Questions
•
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•
•
What is casting?
•
What is the use of pattern?
•
What are used for making pattern?
What is the composition of green sand? •
Write some defects in casting?
What is the use of runner?
What is the use of riser?
Give some advantage of sand casting
What is metal spinning process? Define
casting?
• When do you make core (or) what is
function of core in moulding sand?
• Mention the specific advantages of
carbon di oxide process?
• Write the composition of good
moulding sand?
Annexure III
What are the reasons for the casting
defects of cold shuts and misrun?
Name four different casting defects.
How casting defects are identified?
Questions
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•
•
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Annexure III
What is meant by furnace?
Mention the main parts of cupola furnace.
Mention the main parts of Electric arc furnace.
Mention the main parts of induction furnace.
Write the advantages of cupola furnace.
Write the advantages of electric arc furnace.
Write the advantages of induction furnace.
Write the disadvantages of cupola furnace.
Write the disadvantages of electric arc furnace.
Write the disadvantages of induction furnace.
List the factors to be considered in the choice of metal melting
furnace?
Annexure IV
Multiple Objective Questions
1. _________________ is an added projection on a pattern and forms a seat to support
and I locate the core in the mould
a) Mould print
b) Core print
c) Drag
d) Cope
2. The maximum quantity of moisture content in the moulding sands can be upto
a) 20%
b) 14%)
c) 8%
d) 2%
3. Cope in foundry practice refers to:
a) Bottom half of moulding box
b) Top half of moulding box
c) Middle portion of the moulding box
d) Coating on the mould face
5. The process in which the casting is removed from the mould is called……..
(Ans: Shake out)
Multiple Objective Questions
5. In foundry technology, hollow castings are produced by using…….
(Ans: Cores)
6. "Drag" in foundry practice refers to:
a) The top-half of the moulding box
b) The middle portion of the moulding box
c) The bottom-half of the moulding box
d) The coating on the moulding surface.
7. What is the most suitable size for the coke that is charged into the blast-furnace?
a) 8 to 25 mm
b) 25 to 75 mm
c) 75 to 150 mm
d) Over 150 mm
8. The metal after being extracted from its ore is in the form of:
a) Slabs
b) Billets
c) Ingots
d) Castings
9. __________________ is the flux added with cupola charge to form slag.
a) Lime
b) Sand
c) Coke
d) Pig iron
Annexure IV
Annexure V
Higher Order Questions
1. What are the pattern allowances? Explain briefly each.
2. Explain different type of patterns.
3. Write the advantages of different type of patterns.
4. Discuss the properties of moulding sand.
5. Explain the core making state its advantages and applications.
6. State the different type of mould. Write a short note on Green sand mould
and shell Moulding
7. Explain briefly the various moulding method used in foundries.
8. Enumerate the casting defects and suggest suitable remedies.
9. Explain the various inspection methods of cast products.
Annexure V
Higher Order Questions
11. Can all the machine parts manufacture by casting? If no . why?
12. How can make the Mirror surface finish casting parts?
13. How to avoid the complication to make the large size of components in casting?
14. How to make irregular contour profile in casting?
15. How can combined heat treatment techniques with casting?
Brain Activation
Answer: