Metal casting Process

Manufacturing Vs Production
Manufacturing:
The process of converting raw materials, components,
or parts into finished goods that meet a customer's
expectations or specifications. Manufacturing
commonly employs a man-machine setup with division
of labor in a large scale production.
Production:
Production is a process of transforming (converting)
inputs (raw-materials) into outputs (finished goods).
So, production means the creation of goods and
services. It is done to satisfy human wants. Thus,
production is a process of transformation.

Manufacturing Vs Production
Manufacturing is a process of converting
raw material in to finished product by using
various processes, machines and energy. it
is a narrow term.
Production is a process of converting inputs
in to outputs. it is a broder term.
Every type of manufacturing can be a part
of production, but every production is
not a manufacturing.

List of top 20 manufacturing countries by total value of manufacturing in US dollars for its noted year
according to Worldbank.
Rank Country/Region Millions of $US Year
World 12,578,627 2014
1
China 3,713,300 2014
European Union 2,566,070 2014
2
United States 2,068,080 2014
Eurozone 1,946,857 2014
3 Japan 850,902 2014
4 Germany 787,503 2014
5 South Korea 389,582 2014
6 India 321,721321,721 20142014
7 Italy 296,611 2014
8 France 283,664 2014
9 United Kingdom 282,675 2014
10 Russia 248,481 2014
11 Brazil 218,799 2014
12 Mexico 216,773 2014
13 Indonesia 186,744 2014
14 Spain 166,594 2014
15 Canada 162,074 2014
16 Switzerland 128,881 2014
17 Turkey 126,365 2014
18 Thailand 112,214 2014
19 Netherlands 95,683 2014
20 Australia 93,461 2016

UNIT I METAL CASTING PROCESSES
Sand Casting : Sand Mould – Type of patterns -
Pattern Materials – Pattern allowances –Moulding
sand Properties and testing – Cores –Types and
applications – Moulding machines– Types and
applications; Melting furnaces : Blast and Cupola
Furnaces; Principle of special casting processes :
Shell - investment – Ceramic mould – Pressure die
casting - Centrifugal Casting - CO2 process – Stir
casting; Defects in Sand casting.

UNIT II JOINING PROCESSES
Operating principle, basic equipment, merits and
applications of: Fusion welding processes : Gas
welding - Types – Flame characteristics; Manual
metal arc welding – Gas Tungsten arc welding -
Gas metal arc welding – Submerged arc welding –
Electro slag welding; Operating principle and
applications of : Resistance welding - Plasma arc
welding – Thermit welding – Electron beam
welding – Friction welding and Friction Stir
Welding; Brazing and soldering; Weld defects:
types, causes and cure.

UNIT-III Metal Forming Processes
Introduction Hot Working and Cold Working of
Metals Forging Processes Open, impression
die forging Closed die forging-forging
operation Rolling of metals-types of rolling Flat
strip rolling-shape rolling operation Defects in
rolled parts Principle of rod and wire drawing-
tube drawing Principle of extrusion Types-hot
and cold extrusion.

UNIT IV SHEET METAL PROCESSES
Sheet metal characteristics – shearing, bending and
drawing operations – Stretch forming operations
– Formability of sheet metal – Test methods –
special forming processes-Working principle and
applications – Hydro forming – Rubber pad
forming – Metal spinning– Introduction of
Explosive forming, magnetic pulse forming, peen
forming, Super plastic forming – Micro forming.

UNIT V MANUFACTURE OF PLASTIC
COMPONENTS
Types and characteristics of plastics – Moulding of
thermoplastics – working principles and typical
applications – injection moulding – Plunger and
screw machines – Compression moulding,
Transfer Moulding – Typical industrial
applications – introduction to blow moulding –
Rotational moulding – Film blowing – Extrusion
– Thermoforming – Bonding of Thermoplastics.

Course Outcomes
1. To Explain different metal casting processes,
associated defects, merits and demerits.
2. To Compare different metal joining processes.
3. To Summarize various hot working and cold
working methods of metals.
4. To Explain various sheet metal making processes.
5. To Distinguish various methods of manufacturing
plastic components.

UNIT I
METAL CASTING PROCESSES

MANUFACTURING PROCESSMANUFACTURING PROCESS
It is a science concerned with the use of processing tools,
equipment, machinery and techniques to change the raw
materials in to a usable form.
Classification:
» Primary Shaping Process
» Machining Process
» Joining Process
» Surface Finishing Process

CASTING
Casting is the process of producing metal parts by pouring
molten metal into the mould cavity of the required shape and
allowing the metal to solidify. The solidified metal piece is
called as “Casting”.
Casting
Conventional
Methods
UnConventional
Methods
Green Sand
Mould
Dry sand
Mould
Investment casting
Co2 MoldingCo2 Molding
Continuous casting
Centrifugal casting
Metal Molding
Shell Molding

FoundryFoundry
A plant where the castings are made is called Foundry.
It’s collection of necessary materials, tools and
equipment to produce castings.
The important Processes involved in Foundry are:
1. Pattern Making
2. Mould Making
3. Casting
MouldMould
Mould is the cavity of the required shape using
moulding sand or other suitable materials.

Steps in Making Sand CastingSteps in Making Sand Casting
Pattern Making
Core Making
Moulding
Melting and Pouring
Cleaning
Inspection

Steps in Sand CastingSteps in Sand Casting

Sand Casting DiagramSand Casting Diagram

1.1. Pattern MakingPattern Making
The pattern is a physical model of the casting
used to make the mould.
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.

2. Core Making2. Core Making
Cores are forms, usually made of sand, which
are placed into a mould cavity to form the
interior surface of castings. The void space
between the core and mould cavity surface
is becomes the casting.

3. Moulding3. Moulding
• A sand mould is formed by packing sand into
each half of the mould. The sand is packed
around the pattern, which is a replica of the
external shape of the casting.
• When the pattern is removed, the cavity that
will form the casting remains.

4. Melting and Pouring4. Melting and Pouring
Melting is usually done in a specifically
designated area of the foundry, and the
molten metal is transferred to the pouring
area where the moulds are filled.

5. Cleaning5. Cleaning
Excess metal, in the form of fins, wires, parting
line fins and gates are removed.
6. Inspection6. Inspection
Inspection of the casting for defects and general
quality is performed by using white lightwhite light
inspection, Pressure Test, Magnetic particleinspection, Pressure Test, Magnetic particle
inspection, Radiographic Test, Ultrasonicinspection, Radiographic Test, Ultrasonic
Test, etc,.Test, etc,.

ADVANTAGES
» Design flexibility
» Reduced costs
» Dimensional accuracy
DISADVANTAGES
» Lot of molten metal is wasted in riser &
gating
» The metal casting process is a labor intensive
process

Casting Terms
1. Flask: A metal or wood frame, without fixed top or
bottom, in which the mold is formed.
Drag - Lower molding flask,
Cope - Upper molding flask,
Cheek - Intermediate molding flask
used in three piece molding.

2. Pattern: It is the replica of the final object
to be made. The mold cavity is made with
the help of pattern.
3. Parting line: This is the dividing line
between the two molding flasks that
makes up the mold. PatternPattern

4. Pouring basin: A small funnel shaped cavity at
the top of the mold into which the molten metal is
poured.
5. Sprue: The passage through which the molten
metal, from the pouring basin, reaches the mold
cavity. In many cases it controls the flow of metal
into the mold.

6. Runner: The channel through which the
molten metal is carried from the sprue to
the gate.
7. Riser: A column of molten metal placed in
the mold to feed the castings as it shrinks
and solidifies. Also known as feed head.
8. Gate: A channel through which the molten
metal enters the mold cavity.

9. Core: A separate part of the mold, made of sand and
generally baked, which is used to create openings
and various shaped cavities in the castings.
10.Chaplets: Chaplets are used to support the cores
inside the mold cavity to take care of its own weight
and overcome the metallostatic force.
11. Vent: Small opening in the mold to facilitate
escape of air and gases.

PATTERN
The pattern is the principal tool during
casting process. It’s the replica of the object to
be made by the casting process.
Pattern is the model of the required casting
made in wood, metal or plastics. It is primarily
used to produce the mould cavity in sand.
Its one of the important tools used for making
cavities in the mould.

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.
Patterns properly made and having finished and
smooth surfaces reduce casting defects.
Properly constructed patterns minimize overall
cost of the casting.

Factor For Selecting Pattern Materials
» The design of casting
» Method of molding
» Number of casting to be produced
» Dimensional accuracy and surface finish required
» Type of casting method
» Shape, complexity and size of casting

The pattern material should beThe pattern material should be::
1. Easily worked, shaped and joined.
2. Light in weight.
3. Strong, hard and durable.
4. Resistant to wear and abrasion .
5. Resistant to corrosion, and to chemical reactions.
6. Dimensionally stable and unaffected by
variations in temperature and humidity.
7. Available at low cost.

Types of Patterns
• Solid or Single piece patternSolid or Single piece pattern
• Split PatternSplit Pattern
• Loose piece patternLoose piece pattern
• Match plate patternMatch plate pattern
• Sweep patternSweep pattern
• Skeleton patternSkeleton pattern
• Segmental patternSegmental pattern
• Shell patternShell pattern

Type of Patterns
1. Solid or Single piece pattern1. Solid or Single piece pattern
It is made from one solid piece. So it is also known as
single piece pattern. It can be easily removed from
sand.
This type of pattern is used only in cases where the
job is very simple and does not create any
withdrawal problems.

2. Split pattern2. Split pattern
A pattern consisting of two pieces is called split
pattern. One half of the pattern rests in the lower
part of the molding box, known as drag and the other
half rests in the upper part of the molding box
known as cope.

3. Loose piece pattern3. Loose piece pattern
In some cases, the casting may have small projections
or overhanging projections. These projections make it
difficult to withdraw the pattern from the mould.
Therefor these projections are made as loose pieces.

4. Match plate pattern4. Match plate pattern
• Match plate pattern-in which the patterns are
mounted for two small dumb bells. It consists of a
flat metal or wooden plate, to which the patterns
and gates are permanently fastened. On either end
of the plate are holes to fit into a standard flask.
• The match plate pattern is almost similar to the
mounted pattern but it can have part of the casting
in the cope and part in the drag like split piece
pattern. These parts are generally attached to the
plate / board in opposite sides in the perfect
positions.

4. Sweep pattern4. Sweep pattern
A sweep pattern is just a form of made on a wooden
board which sweeps the shape of the casting into the
sand all around the circumference. It rotates about
the post.

5. Skeleton pattern5. Skeleton pattern
• A skeleton pattern is the skeleton of desired shape.
The skeleton frame is mounted on a metal base.
• It’s made from wooden stripswooden strips.
• Its filled with sandsand and is rammed.rammed.
• If the object is symmetrical like a pipepipe, the two
halves (of the pipe) can be molded by using the
same pattern and then the two molds can be
assembled before pouring the molten metal.

6. Segmental pattern6. Segmental pattern
It is used for large ring shaped casting. A vertical
central spindle is firmly fixed near the centre of a
drag flask.

7. Shell pattern7. Shell pattern
Shell moulding, is an expendable mold
casting process that uses a resin covered sand to
form the mold. As compared to sand casting, this
process has better dimensional accuracy, a higher
productivity rate, and lower labor requirements.
It is used for small to medium parts that require high
precision.
However, in shell mold casting, the mold is a thin-
walled shell created from applying a sand-resin
mixture around a pattern.

• The pattern, a metal piece in the shape of
the desired part, is reused to form multiple
shell molds. A reusable pattern allows for
higher production rates, while the
disposable molds enable complex
geometries to be cast.

Pattern Allowances
Pattern allowance is a vital feature as it affects
the dimensional characteristics of the
casting. When the pattern is produced,
certain allowances must be given on the
sizes specified in the finished component
drawing.
The selection of correct allowances greatly
helps to reduce machining costs and
rejections.

Types of pattern allowances
• Shrinkage or contraction allowanceShrinkage or contraction allowance
• Draft or taper allowanceDraft or taper allowance
• Machining or finish allowanceMachining or finish allowance
• Distortion or camber allowanceDistortion or camber allowance
• Rapping allowanceRapping allowance

1. Shrinkage allowance1. Shrinkage allowance
After pouring the molten metal into the mould, the
metal will solidify and will reduce in size. To
compensate this, the pattern is made larger than
the required casting. This increase in size on
pattern for metal Shrinkage is called Shrinkage
allowance.

Shrinkage allowance for various metals are
Cast iron-10mm/m
Steel-15mm/m
Brass-14mm/m
Aluminium-18mm/m

2. Draft Allowance2. Draft Allowance
Edges of the mould may get damaged when it is
removed from the sand. To avoid this taper is
given to all vertical walls of the pattern. This taper
given on the vertical sides of the pattern is called
draft allowance

3. Machining /Finish allowance3. Machining /Finish allowance
The finish and accuracy achieved in sand casting are
generally poor and therefore when the casting is
functionally required to be of good surface finish or
dimensionally accurate, it is generally achieved by
subsequent machining.
Machining or finish allowances are therefore added in
the pattern dimension. The amount of machining
allowance to be provided for is affected by the
method of molding and casting.

4. Distortion / Camber allowance4. Distortion / Camber allowance
The distortion in casting may occur due to
internal stresses. These internal stresses are
caused on account of unequal cooling of
different section of the casting and hindered
contraction.
Sometimes casting get distorted, during
solidification due to their shape.
ex: letter U,V,T and L etc.

Rapping / Shake allowanceRapping / Shake allowance
The pattern is shacked or wrapped to take it
out of mould. This in turn enlarges the mould
cavity. Hence negative allowance is given to
pattern.
If the drag angle is provided, shake allowance
reduces.
The pattern is shacked from side to side before
removing the pattern from the mould.

Properties of mould sand
• Porosity
• Permeability
• Plasticity
• Cohesiveness
• Adhesiveness
• Refractoriness
• Collapsibility

Porosity
• How much water rock or soil can retain.
Percentage of volume that is void space.
• Porosity or void fraction is a measure of the
void (i.e. "empty") spaces in a material, and
is a fraction of the volume of voids over the
total volume.

• Porosity: Percent of volume that is void space.
– Sediment: Determined by how tightly packed
and how clean (silt and clay), (usually between
20 and 40%)
– Rock: Determined by size and number of
fractures (most often very low, <5%)

Permeability
• Permeability is a measure of how easily
water can travel through porous soil or
bedrock.
• They can hold a lot of water, and it flows
easily through them.
• During pouring and subsequent
solidification of a casting, a large amount of
gases and steam is generated.
• If these gases are not allowed to escape
from the mould, they would be entrapped
inside the casting and cause casting defects.

• Permeability: Ease with which water will flow
through a porous material
– Sediment: Proportional to sediment size
• Gravel Excellent
• Sand Good
• Silt Moderate
• Clay Poor
– Rock: Proportional to fracture size and number.
Can be good to excellent (even with low porosity)

Plasticity
• It is the ability of the sand to get compacted and
behave like a fluid.
• It will flow uniformly to all portions of pattern
when rammed and distribute the ramming
pressure evenly all around in all directions.
• The quality of being easily shaped or moulded.

Cohesiveness/ Strength
It is property of moulding sand by which
it sticks together.
A moulding sand should have sufficient
strength so that the mould does not
collapse or get partially damaged
during shifting and pouring the molten
metal.

Adhesiveness
• This is the property of moulding sand by
which it adheres to another body. The
moulding sand should stick to the moulding
boxes. So it does not fall out when the flasks
are lifted and turn over.
• This property depends on the type and
amount of binder used in the mix. Addition
of clay and moisture increases the
adhesiveness.

Refractoriness
• This is the property of moulding sand to
withstand the temperature of the molten
metal to be poured. So that It does not get
cracked and fused with the metal.
• Poor refractoriness will result the rough
surface in casting.

Collapsibility
• This property permits the moulding sand to
collapse easily after the casting solidifies.
• If the mould or core does not collapse, it
may restrict the free contraction of the
solidification material and cause cracks on
the casting.
• This property depends on the amount of
quartz and binder.

Sand TestingSand Testing
Following tests of sand are used for molding.
» Moisture content test.
» Clay content test.
» Fineness test.
» Permeability test.
» Compression test.
» Hardness test.
» Refractoriness test

Moisture content TestMoisture content Test
• Moisture is the property of the moulding
sand it is defined as the amount of water
present in the moulding sand.
• Low moisture content in the moulding sand
does not develop strength properties. High
moisture content decreases permeability.

Procedures are:Procedures are:
1. 20 to 50 gms of prepared sand placed in the pan and
heated by an infrared heater bulb for 2 to 3 minutes.
2. The moisture in the moulding sand is thus
evaporated.
3. Moulding sand is taken out of the pan and
reweighed.
4. The percentage of moisture can be calculated from
the difference in the weights, of the original moist
and the consequently dried sand samples.
Percentage of moisture content = (W1-W2)/(W1) %Percentage of moisture content = (W1-W2)/(W1) %
• W1-Weight of the sand before drying,
• W2-Weight of the sand after drying.

Moisture content Test EquipmentMoisture content Test Equipment

Clay content testClay content test
Clay influences strength, permeability and other
moulding properties. It is responsible for bonding
sand particles together.
1. Small quantity of prepared moulding sand dried
2. Separate 50 gms of dry moulding sand and transfer
wash bottle.
3. Add 475cc of distilled water + 25cc of a 3% NaOH.
4. Agitate this mixture about 10 minutes with the help
of sand stirrer.
5. Fill the wash bottle with water up to the marker.

6. After the sand etc., has settled for about 10
minutes, Siphon out the water from the wash
bottle.
7. Dry the settled down sand.
8. The clay content determined from the difference
in weights of the initial and final sand samples.
Percentage of clay content = (W1-W2)/(W1) * 100Percentage of clay content = (W1-W2)/(W1) * 100
Where,
W1-Weight of the sand before drying,
W2-Weight of the sand after drying.

Clay content test EquipmentClay content test Equipment

Fineness test
The grain size, distribution, grain fitness are
determined with the help of the fitness testing of
moulding sands. The apparatus consists of a
number of standard sieves mounted one above the
other, on a power driven shaker.
• The shaker vibrates the sieves and the sand placed
on the top sieve gets screened and collects on
different sieves depending upon the various sizes of
grains present in the moulding sand.
• The top sieve is coarsest and the bottom-most sieve
is the finest of all the sieves. In between sieve
placed in order of fineness from top to bottom.

1. Sample of dry sand (clay removed sand) placed in
the upper sieve
2. Sand vibrated for definite period
3. The amount of same retained on each sieve
weighted.
4. Percentage distribution of grain is computed.

Permeability test
The quantity of air that will pass through a standard
specimen of the sand at a particular pressure
condition is called the permeability of the sand.
Following are the major parts of the permeability
test equipment:
1. An inverted bell jar, which floats in a water.
2. Specimen tube, for the purpose of hold the
equipment
3. A manometer (measure the air pressure)

Steps involved are:Steps involved are:
1. The air (2000cc volume) held in the bell jar
forced to pass through the sand specimen.
2. At this time air entering the specimen equal
to the air escaped through the specimen
3. Take the pressure reading in the manometer.
4. Note the time required for 2000cc of air to
pass the sand.
5. Calculate the permeability number

6. Permeability number (N) = ((V x H) / (A x P x T))Permeability number (N) = ((V x H) / (A x P x T))
Where,
V-Volume of air (cc)
H-Height of the specimen (mm)
A-Area of the specimen (mm2)
P-Air pressure (gm / cm2)
T-Time taken by the air to
pass through the sand (seconds)

Compression test
Measurements of strength of moulding sands
carried out on the universal sand strength
testing machine. The strength measured
such as compression, shear and tension.
Green compression strength or simply green
strength generally refers to the stress
required to rupture the sand specimen under
compressive loading.

The sand specimen taken out of the specimen
tube and immediately (any delay causes the
drying of the sample which increases the
strength) put on the strength testing
machine and the force required to cause the
compression failure is determined.
The green strength of sands is generally in
the range of 30 to 160 KPa.

Hardness test
Hardness of the mould surface tested with the
help of an “indentation hardness tester”. It
consists of indicator, spring loaded spherical
indenter.
The spherical indenter is penetrates into the
mould surface at the time of testing. The
depth of penetration w.r.t. the flat reference
surface of the tester.

Mould hardness number = ((P) / (D – (D2-d2))Mould hardness number = ((P) / (D – (D2-d2))
Where,
P- Applied Force (N)
D- Diameter of the indenter (mm)
d- Diameter of the indentation (mm)

Refractoriness test
The refractoriness used to measure the ability of
the sand to withstand the higher temperature.
Steps involved are:
1. Prepare a cylindrical specimen of sand
2. Heating the specimen at 1500 C for 2 hours
3. Observe the changes in dimension and
appearance
4. If the sand is good, it retains specimen share
and shows very little expansion. If the sand is
poor, specimen will shrink and distort.

Moulding ToolsMoulding Tools
• Showel
• Riddle
• Rammer
• Trowel
• Slick
• Lifter
• Strike-off bar
• Sprue pin
•Bellow
•Swab
•Gate cutter
•Mallet
•Vent Rod
•Draw spike
•Clamps
•Moulding boxes

Showel
Riddle
Rammer
Trowel
Slicks

Lifter Strike-off bar
Sprue pin
Bellow

Swab Gate cutter
Mallet
Vent Rod
Draw spike Clamps
Moulding boxes

CORESCORES
A core is a body made of sand which is used
to make a cavity or a hole in the casting. The
shape of the core is similar to the required
cavity in the casting to be made.
It is used to form a holes, projections,
Undercuts and Internal Cavities in a casting
for different purpose.

Types of CoresTypes of Cores
• According to the state of core
 Green sand core
 Dry sand core
• According to the position of the core in the
mould
 Horizontal core
 Vertical core
 Balanced core
 Hanging core
 Drop core

Green sand coreGreen sand core
It is formed by the pattern itself. When the
pattern leaves a core as a part of the mould,
then the body of sand is called Green Sand
Core.
Dry Sand coreDry Sand core
It is made separately and positioned in the
mould. These cores are most commonly
used.

Horizontal CoreHorizontal Core
It is used to provide a hole in the casting from
one end to other end and lies axially
horizontal. The both ends of the core are
supported in the mould.

Vertical coreVertical core
This is similar to horizontal core but lies
axially Vertical. It is supported by in drag
and core.

Balanced coreBalanced core
This is just like a cantilever. Its only one end is
supported in mould and other end is free.

Hanging coreHanging core
It is supported only at the top in the cope and
there is no support at the bottom.

Drop coreDrop core
A drop core is required when hole is not line
with the parting surface but must be formed
at lower level.

Moulding machineMoulding machine
For mass production, moulding is done using
moulding machines.
Advantages
• Faster production rate
• Production cost
• Higher product quality

ClassificationClassification
• Squeezer moulding machine
• Jolting machine
• Sand slinger

Squeezer moulding machine
• These machines are operated by
compressed air at a pressure from 5 to 7
atm.
• A mold plate with pattern is clamped on the
work table.
• The flask is placed on the mold plate
• Then the sand frame is placed on the flask
• The flask and frame are filled with moulding
sand.

Squeezer Molding MachineSqueezer Molding Machine
• Now by table lift mechanism the flask
together with sand frame and pattern is
lifted up against the platen of squeeze head
• The platen enters the sand frame and
presses the moulding sand

Jolting MachineJolting Machine
• The pattern and flask are mounted on a mold
plate.
• The flask is filled with sand.
• The table with moulding sand is lifted by
plunger when compressed air is passed
through pipe and channels.
• When the air is released through the hole, the
table will be dropped.

• In falling, the table strikes the stationary
guiding cylinder and this impact packs the
moulding sand in the flask.
• To reduce noise, vibration springs are used to
cushion the table.
• About 20 to 50 drops20 to 50 drops are needed to compact
the sand, and the average machine operates at
200 strokes per min200 strokes per min.

Sand SlingerSand Slinger
• In this machine the sand is thrown out of
the box by means of centrifugal force from
an impeller.
• The impeller head consists of housing in
which blade rotates at high speed.
• Molding sand is fed by a belt conveyor to
thee housing.
• The impeller head throws the sand through
the outlet with a high velocitya high velocity.

• So the sand gets rammed around the
pattern
• The density of the sand can be controlled by
the speed of the blade.
• This type of machine is used for heavy
moulds.

Green Sand Molding
• The process utilizes a mould made of
compressed or compacted moist sand.
• The term "green" denotes the presence of
moisture in the Moulding sand.
• The mould material consists of silica sand
mixed with a suitable bonding agent (usually
clay) and moisture.

Advantages
» Most metals can be cast by this method.
»Pattern costs and material costs are
relatively low.
Disadvantages
» Surface Finish of the castings obtained by
this process is not good

Sand Mold Making Procedure
1. A flat board is placed on the floor
2. One half of the pattern is placed on the
moulding board.
3. Drag box is placed around the pattern.
4. Drag is now filled up with green sand.
5. Then ramming is done by means of hand
rammer.
6. After ramming excess sand is removed by
strike off bar.

7. Vent wire is used to make vent holes in
number of places by which the gas will
escape when molten metal is poured.
8. Now the drag is tilted upside down.
9. Dry parting sand is sprinkled over the
upper side to prevent the sand in the cope
from sticking to the sand in the drag.
10.Top half of the pattern is now fixed in
position, with a cope box correctly placed
on the drag.
11.Sprue and riser pins are fixed in position.

12. Cope is now filled with green sand.
13. Filling, ramming and venting of the cope is
done similarly to that of drag.
14. Sprue and riser pins are remove.
15. Cope and drag are separated.
16. A small passage known as gate is cut at the
bottom of the Sprue opening to pour the
molten metal.
17. Mould surface may be coated with silica flour
and graphite to give smooth surface to the
casting and reduces surface defects.
18. The mould is now ready for molding.

Shell Molding Process
• Shell-mold casting yields better surface quality
and tolerances
• The 2-piece pattern is made of metal (e.g.
aluminium or steel), it is heated to between
175°C- 370°C, and coated with a lubricant, e.g.
silicone spray
• Each heated half-pattern is covered with a
mixture of sand and a thermoset resin/epoxy
binder. The binder glues a layer of sand to the
pattern, forming a shell. The process may be
repeated to get a thicker shell

• The assembly is baked to cure it.
• The patterns are removed, and the two half-
shells joined together to form the mold; metal
is poured into the mold.
• When the metal solidifies, the shell is broken to
get the part.

AdvantagesAdvantages
Better surface finish on casting
Good dimensional accuracy
Machining often not required
Can be mechanized for mass production
DisadvantagesDisadvantages
More expensive metal pattern
Difficult to justify for small quantities

Investment Casting
• Produces very high surface quality and
dimensional accuracy
• Commonly used for precision equipment
such as surgical equipment, for complex
geometries and for precious metals
• This process is commonly used by artisans
to produce highly detailed artwork

• The first step is to produce a pattern or
replica of the finished mould. Wax is most
commonly used to form the pattern, although
plastic is also used.
• Patterns are typically mass-produced by
injecting liquid or semi-liquid wax into a
permanent die.
• Prototypes, small production runs and
specialty projects can also be undertaken by
carving wax models.

• Cores are typically unnecessary but can be
used for complex internal structures.
• Rapid prototyping techniques have been
developed to produce expendable patterns.
• Several replicas are often attached to a gating
system constructed of the same material to
form a tree assembly. In this way multiple
castings can be produced in a single pouring.

Die Casting (Pressure Die Casting)

Die Casting (Pressure Die Casting)
• Die casting is a very commonly used type of
permanent mold casting process.
• It is used for producing many components of
home appliances (e.g. rice cookers, stoves,
fans, washing and drying machines, fridges,
motors, toys and hand-tools).
• The molten metal is injected into mold cavity
(die) under high pressure (7-350MPa)
Pressure maintained during solidification.

• Hot Chamber (Pressure of 7 to 35MPa)
• The injection system is submerged under the
molten metals (low melting point metals such
as lead, zinc, tin and magnesium)
• Cold Chamber (Pressure of 14 to 140MPa)
• External melting container (in addition
aluminium, brass and magnesium)
• Melds are made of tool steel, mold steel,
maraging steel, tungsten and molybdenum.
• Single or multiple cavity

• Lubricants and Ejector pins to free the parts
• Venting holes and passageways in die
• Formation of flash that needs to be trimmed
Advantages
» High production
» Economical
» Close tolerance
» Good surface finish
» Thin sections
» Rapid cooling

Hot-Chamber Die Casting
• In a hot chamber process (used for Zinc alloys,
magnesium) the pressure chamber connected
to the die cavity is filled permanently in the
molten metal.
• The basic cycle of operation is as follows:
(i) Die is closed and gooseneck cylinder is filled
with molten metal;
(ii) Plunger pushes molten metal through
gooseneck passage and nozzle and into the die
cavity; metal is held under pressure until it
solidifies;

(iii) Die opens and cores, if any, are retracted;
casting stays in ejector die; plunger returns,
pulling molten metal back through nozzle and
gooseneck;
(iv) Ejector pins push casting out of ejector die.
As plunger uncovers inlet hole, molten metal
refills gooseneck cylinder.
The hot chamber process is used for metals that
(a) Have low melting points and
(b) Do not alloy with the die material; common
examples are tin, zinc, and lead.

800 ton hot chamber die casting machine, DAM 8005. This is
the largest hot chamber machine in the world and costs about
$1.25 million.

Cold Chamber Die Casting
In a cold chamber process, the molten metal is poured
into the cold chamber in each cycle. The operating
cycle is
(i) Die is closed and molten metal is ladled into the cold
chamber cylinder;
(ii) Plunger pushes molten metal into die cavity; the
metal is held under high pressure until it solidifies;
(iii) Die opens and plunger follows to push the solidified
slug from the cylinder, if there are cores, they are
retracted away;
(iv) Ejector pins push casting off ejector die and plunger
returns to original position

Advantages
• Parts of great complexity
• good surface finish
• Wax can usually be recovered for reuse
Disadvantages
» Many processing steps are required
» Relatively expensive process

Ceramic mould
This process is expensive, but can eliminate secondary
machining operations. Typical parts made from this
process include impellers made from stainless steel,
bronze, complex cutting tools, plastic mold tooling.
Similar to plaster mold casting except that mold is
made of refractory ceramic material that can withstand
higher temperatures than plaster.
It can be used to cast steels, Cast irons and other high
temperature alloys.

• MixingMixing the ceramic powder with 30% - 40% of a
binder – low melt polymer.
• InjectionInjection of the warm powder with molten binder
into the mold by means of the screw.
• Removal of the partRemoval of the part from the mold after cooling
down of the mixture.
• DebindingDebinding – removal of the binder. There are two
Debinding methods:
– Solvent DebindingSolvent Debinding – the binder is dissolved by
a solvent or by water;
– Thermal DebindingThermal Debinding – the binder is heated
above the volatilization temperature.

• The essential feature of centrifugal casting
is the introduction of liquid metal into a
rotating mould.
• Centrifugal force plays a major role in
shaping of casting
• The centrifugal casting machine contains a
die surrounded by cooling water
• Machine is mounted on a wheel and can be
moved length wise.

• The metal is poured into the mould through a
long spout.
• The mould rotates on its own axis.
• Die to centrifugal force the molten metal is
thrown to the walls of the mould.
• Since it is water cooled the molten metal
solidifies immediately.
• This method is used for producing cylinder
objects

• Production rate is high
• Core is not required
• Defect is very less
• Patterns, runners and risers are not required.
DisadvantagesDisadvantages
• It is suitable only for cylindrical shaped castings
• Skilled worker is required
• Maintenance cost is high
• Less safety

CO2 Moulding
• A sand molding technique and uses sand
grain in which is mixed a solution of sodium
silicate that acts to bind the sand particles.
• CO2 gas is used to harden the sand after the
mould has been prepared.
H2O+Na2SiO3+ CO2 →Na2CO3+SiO2

COCO22 CastingCasting is a kind of sand casting
process. In this process the sand moulding
mixture is hardenedhardened by blowing gas over
the mould.
In addition, one can be sure of getting
dimensionally accuratedimensionally accurate castings with finefine
surface finishsurface finish. But, this process is not
economical than green sand casting process.
The process is basically a hardening processhardening process
for moulds and cores.

The principle of working of the co2 process is
based on the fact that if co2 gas is passed
through a sand mix containing sodium silicate,
the sand immediately becomes extremely
strongly bonded as the sodium silicate
becomes a stiff gel.
This gel is responsible for giving the necessary
strength to the mould.
The sand used for the process must be dry and
free from clay. Suitable additives such as coal
powder, wood flour, graphite may be added to
improve certain properties like collapsibility.

The suitable sand mixture can then be
packed around the pattern in the flask or in
the core box by machines or by hand.
When the packing is complete, co2 is forced
into the mould at a pressure of about 1.45
kgf/cm2(142 kn/m2) . The gas is inert upto
15 to 30 seconds.
The volume of CO2 required can be
calculated if the quantity of sodium silicate
present is known.

As a thumb rule, for every 1 kg of sodium
silicate, 0.50-0.75 kg of gas is required.
Over gassing is wasteful and results in
deteriorating the sand.
Patterns used in this process may be made of
wood, metal or plastic.
Carbon dioxide casting is favoured both by
the commercial foundry men and hobbyist for
a number of reasons. In commercial
operations, foundry men can assure
customers of affordable castings which
require less machining.

Compared to other casting methods cores and
moulds are strong.
Reduces fuel cost since gas is used instead of
to other costly heating generating elements.
Operation is speedy. Moulds and cores can be
immediately after processing.
Great dimensional accuracy can be attained
than other moulding or core making process.
Semi-skilled labour can be used.
This process can be fully automated.

Stir Casting
• Stir casting is done by introducing fibres of
particles into molten or partially solidified
metals/alloy followed by casting in moulds.
• The main advantages are the simplicity,
flexibility and cost efficiency.
• The stir casting process begins with
preparation of the selected metallic matrix
material followed by cooling it to a semi solid
state.

Comparison of Casting ProcessesComparison of Casting Processes

FurnacesFurnaces
A furnace is a device used for high-temperature
heating. The name derives from Greek
word fornax, which means oven. The heat
energy to fuel a furnace may be supplied
directly by fuel combustion, by electricity such
as the electric arc furnace, or through
induction heating in induction furnaces.
Industrial Furnaces:
• Cupola FurnaceCupola Furnace
• Blast FurnaceBlast Furnace

Cupola FurnaceCupola Furnace
A cupola or cupola furnace is a melting device
used in foundries that can be used to melt
cast iron, Ni-resist iron and some bronzes. The
cupola can be made almost any practical size.
The size of a cupola is expressed in diameters
and can range from 1.5 to 13 feet (0.5 to
4.0 m). The overall shape is cylindrical and the
equipment is arranged vertically, usually
supported by four legs. The overall look is
similar to a large smokestack.

Operation of Cupola
It is used for melting scrap metal the pig iron
used in the production of casting.
Operation of Cupola
•Preparation of cupola
•Firing
•Charging and melting
•Slagging and metal tapping
•Dropping down the cupola bottom

Zones of cupola
• Combustion or oxidizing zone- It is situated
normally 15 cm to 30 cm above the top of the
tuyeres
C +o2 Co→ 2+heat (1550 c to 1850 c)◦ ◦
• Reducing zone- It is above the combustion
zone. it has reducing atmosphere and thus
protects from oxidation, the metal charge
above and that dropping through it.
(Temperature 1200◦
C)

• Melting Zone- it starts from the first layer of
metal charge above the coke bed and extends
upto a height of 0.09m or less. Iron starts to
melting in this zone (Tempeture 1600 c)◦
• Preheating Zone- it starts from above the
melting zone and extends upto the bottom of
the charging door. it contains cupola charge
as alternate layers of coke, limestone and
metal (Temperature 1100 c)◦
• Stack Zone- hot gases from cupola pass
through the stack zone and escape to
atmosphere.

Advantages
• It is simple and economical to operate
• It is capable of accepting wide range of
materials without reducing melt quality.
• It can refine the metal charge, removing the
impurities out of the slag.
• It can be used as a continuous process.
• High melting rate
• Easy to operate
• Efficiency of cupola various from 30% to 50%

The purpose of a blast furnace is to chemically
reduce and physically convert iron oxides into
liquid iron called "hot metal". The blast
furnace is a huge, steel stack lined with
refractory brick, where iron ore, coke and
limestone are dumped into the top, and
preheated air is blown into the bottom.

A blast furnace is a type of metallurgical furnace
used for melting to produce industrial metals,
generally iron, but also others such as lead or
copper.

• In a blast furnace, fuel, ore, and flux
(limestone) are continuously supplied
through the top of the furnace, while a hot
blast of air (sometimes with oxygen
enrichment) is blown into the lower section
of the furnace through a series of pipes
called tuyeres, so that the chemical
reactions take place throughout the furnace
as the material moves downward.

• The end products are usually molten metal
and slag phases tapped from the bottom,
and flue gases exiting from the top of the
furnace.
• The downward flow of the ore and flux in
contact with an up flow of hot, carbon
monoxide-rich combustion gases is a
counter current exchange process.
• In contrast, air furnaces (such as
reverberator furnaces) are naturally
aspirated, usually by the convection of hot
gases in a chimney flue

• According to this broad definition, bloomers
for iron, blowing houses for tin, and smelt
mills for lead would be classified as blast
furnaces.
• However, the term has usually been limited
to those used for smelting iron ore to
produce pig iron, an intermediate material
used in the production of commercial iron
and steel, and the shaft furnaces used in
combination with sinter plants in base
metals smelting.

Casting Defects
a) Misruns b) Cold Shut c) Shrinkage Cavity
d) Microporosity f) Mismatch

Misrun
• Fluidity of the molten metal is insufficient,
• Pouring Temperature is too low,
• Pouring is done too slowly and/or
• Cross section of the mold cavity is too thin.

Cold Shut
A cold shut occurs when two portion of the
metal flow together, but there is lack of fusion
between them due to premature freezing, Its
causes are similar to those of a Misruns.

Shrinkage Cavity- This defects is a depression in
the surface or an internal void in the casting
caused by solidification shrinkage that restricts
the amount of the molten metal available in the
last region to freeze.

Micro porosity- This refers to a network of a
small voids distributed throughout the casting
caused by localized solidification shrinkage of
the final molten metal in the dendritic
structure.

Mismatch- There is a mismatching of top and
bottom parts parts of the casting at the mould
join.

Metal casting Process

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