PART-B (16 Marks)
UNIT I
1. With reference to metal casting, explain the following types of patterns, with suitable
sketches of examples
(i) Solid pattern
these types of patterns are made of single solid pieces without
joints, partings or loose piece.
It is made exactly into the desired casting to be produced with some
allowances
ii) Split pattern
Split pattern is made into two pieces.
One part is used to produce the lower half of
the mould whereas the other part is used to
produce the upper half of the mould.
Two parts are assembled together in correct
position by pins called dowel pin.
(iii) Loose piece pattern
It is frequently the case that parts of the pattern will
overhang so that the pattern cannot be removed from the sand in
any direction, even if parted. In such cases the overhanging
parts are fastened loosely to the main part of the pattern
bywiresor woodenpins.
(iv) Sweep pattern
A sweep is a section or
board (wooden) of
proper contour that is
rotated about one edge
to shape mould cavities
having shapes of rotational symmetry. This type of pattern is used when a casting of large size is
to be produced in a short time. Large kettles of C.I. are made by sweep patterns.
2. Explain the CO2 process of core making. State its advantages and applications.
Carbon Dioxide Moulding
This sand is mixed with 3 to 5 % sodium
silicate liquid base binder in muller for 3 to 4
minutes.
Additives such as coal powder, wood flour sea
coal, 2extrin may be added to improve its
properties.
Aluminium oxide Kaolin clay may also added
to the sand.
Patterns used in this method may be coated with
Zinc of 0.05 mm to 0.13 mm and then spraying
a layer of aluminium or brass of about 0.25 mm
thickness for good surface finish and good
results.
Advantages

Operation is speedy since we can use the mould and cores immediately after
processing.

Heavy and rush orders.

Floor space requirement is less.

Semi skilled labour may be used.
3. With suitable sketches, explain the various steps of investment casting Process. What are
its advantages?
Investment Casting
 Investment casting produces very high surface quality and dimensional accuracy.
 Investment casting is 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.
WAX
 The first step is to produce a pattern
SPUR
or replica of the finished mould. Wax is most
commonly used to form the pattern, although plastic
WAX
is also used.
PATTERN
 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.
HEAT
WAX
Advantages

Parts of great complexity and intricacy can be cast

Close dimensional control and good surface finish

Wax can usually be recovered for reuse

Additional machining is not normally required –
this is a net shape process
Disadvantages

Many processing steps are required

Relatively expensive process
4. Sketch the various sand casting defects. Give their cause and remedies?
There are numerous opportunities in the casting operation for different defects to
appear in the cast product. Some of them are common to all casting processes.
Missruns:
Casting solidifies before completely fill the mold.
Reasons are low pouring temperature, slow pouring or
thin cross section of casting.
Cold shut:
Two portions flow together but without fusion between
them. Causes are similar to those of a misrun.
Cold shots:
When splattering occurs during pouring, solid
globules of metal are entrapped in the casting.
Proper gating system designs could avoid this
defect.
Shrinkage cavity:
Voids resulting from shrinkage. The problem can often be
solved by proper riser design but may require some
changes in the part design as well.
Microporosity:
Network of small voids distributed throughout the
casting. The defect occurs more often in alloys, because
of the manner they solidify
Hot tearing:
Cracks caused by low mold collapsibility. They
occur when the material is restrained from
contraction during solidification. A proper mold
design can solve the problem.
Some defects are typical only for some particular
casting processes, for instance, many defects occur
in sand casting as a result of interaction between the sand mold and the molten metal.
Defect found primarily in sand casting are gas cavities, rough surface areas, shift of the
two halves of the mold, or shift of the core, etc.
5. List out various pattern allowances. Explain them in detail.
To compensate for any dimensional and structural changes which will happen during the
casting or patterning process, allowances are usually made in the pattern.
Contraction allowances / Shrinkage allowance
The pattern needs to incorporate suitable allowances for shrinkage; these are
called contraction allowances, and their exact values depend on the alloy being cast and the
exact sand casting method being used. Some alloys will have overall linear shrinkage of up to
2.5%, whereas other alloys may actually experience no shrinkage or a slight “positive”
shrinkage or increase in size in the casting process (notably type metal and certain cast irons).
The shrinkage amount is also dependent on the sand casting process employed, for example
clay-bonded sand, chemical bonded sands, or other bonding materials used within the sand.
This was traditionally accounted for using a shrink rule, which is an oversized rule.
Draft allowance
When the pattern is to be removed from the sand mold, there is a possibility that any
leading edges may break off, or get damaged in the process. To avoid this, a taper is provided
on the pattern, so as to facilitate easy removal of the pattern from the mold, and hence reduce
damage to edges. The taper angle provided is called the Draft angle. The value of the draft
angle depends upon the complexity of the pattern, the type of molding (hand molding or
machine molding), height of the surface, etc. Draft provided on the casting 1 to 3 degrees on
external surface.
Finishing or Machining allowance
The surface finish obtained in sand castings is generally poor (dimensionally inaccurate),
and hence in many cases, the cast product is subjected to machining processes like turning
or grinding in order to improve the surface finish. During machining processes, some metal is
removed from the piece. To compensate for this, a machining allowance (additional material)
should be given in the casting.
Shake allowance
Usually during removal of the pattern from the mold cavity, the pattern is rapped all
around the faces, in order to facilitate easy removal. In this process, the final cavity is
enlarged. To compensate for this, the pattern dimensions need to be reduced. There are no
standard values for this allowance, as it is heavily dependent on the personnel. This
allowance is a negative allowance, and a common way of going around this allowance is to
increase the draft allowance.Shaking of pattern causes enlargement of mould cavity and
results in a bigger casting.
Distortion allowance
During cooling of the mold, stresses developed in the solid metal may induce distortions
in the cast. This is more evident when the mold is thinner in width as compared to its length.
This can be eliminated by initially distorting the pattern in the opposite direction.
6. Discuss any four sand testing methods.
 Moisture content test

Clay content test.

Permeability test

Strength test

Deformation and toughness test

Hot strength test

Refractoriness test
7. Explain the properties of moulding sands.
Molding sands
Molding sands, also known as foundry sands, are defined by eight characteristics:
refractoriness, chemical inertness, permeability, surface finish, cohesiveness, flowability,
collapsibility, and availability/cost.
Refractoriness:
This refers to the sand’s ability to withstand the temperature of the liquid metal being cast
without breaking down. For example some sands only need to withstand 650 °C (1,202 °F) if
casting aluminum alloys, whereas steel needs a sand that will withstand 1,500 °C (2,730 °F).
Sand with too low a refractoriness will melt and fuse to the casting.
Chemical inertness:
The sand must not react with the metal being cast. This is especially important with
highly reactive metals, such asmagnesium and titanium.
Permeability:
This refers to the sand’s ability to exhaust gases. This is important because during the
pouring process many gases are produced, such as hydrogen, nitrogen, carbon dioxide,
and steam, which must leave the mold otherwise casting defects, such as blow holes and gas
holes, occur in the casting. Note that for each cubic centimeter (cc) of water added to the
mold 16,000 cc of steam is produced.
Surface finish:
The size and shape of the sand particles defines the best surface finish achievable, with
finer particles producing a better finish. However, as the particles become finer (and surface
finish improves) the permeability becomes worse.
Cohesiveness (or bond):
This is the ability of the sand to retain a given shape after the pattern is removed.
Flowability:
The ability for the sand to flow into intricate details and tight corners without special
processes or equipment.
Collapsibility:
This is the ability of the sand to be easily stripped off the casting after it has solidified.
Sands with poor collapsibility will adhere strongly to the casting. When casting metals that
contract a lot during cooling or with long freezing temperature ranges a sand with poor
collapsibility will cause cracking and hot tears in the casting. Special additives can be used to
improve collapsibility.
8. What is core? Describe the different types of core used.
Green-sand cores
Green-sand cores makes casting long narrow features difficult or impossible. Even for
long features that can be cast it still leave much material to be machined. A typical
application is a through hole in a casting.
Dry sand core
Horizontal core
Vertical core
Balanced core
Hanging core
9. Shell moulding process, product and applications.
Steps in shell-molding:
Shell-mold casting yields better surface quality and tolerances. The process is described
as follows
The
made
2-piece
of
pattern
metal
is
(e.g.
aluminum or steel), it is
heated to between 175°C370°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 halfshells joined together to form the mold; metal is poured into the mold. When
the metal solidifies, the shell is broken to get the part.
Smoother cavity surface permits easier flow of molten metal and better surface finish on
casting.
Good dimensional accuracy.
Machining often not required.
Mold collapsibility usually avoids cracks in casting.
10. Describe the operation of cupola furnace for melting cast iron?
Cupola Furnace
A continuous flow of iron emerges from the bottom of the furnace.
Depending on the size of the furnace, the flow rate can be as high as 100 tonnes per hour.
At the metal melts it is refined to some extent, which removes contaminants. This makes
this process more suitable than electric furnaces for dirty charges.
11. How is green sand mould prepared?

Diagram

Procedure
12. Give the sequence of steps in die casting of a part in hot chamber process.

Diagram

procedure
13. Explain in detail the working principle of centrifugal casting.
Centrifugal casting
Centrifugal casting uses a permanent mold that is rotated about its axis at a speed
between 300 to 3000 rpm as the molten metal is poured
c
e
n
trifugal forces cause the metal to be pushed out towards the mold walls, where it
solidifies after cooling.
Centrifugal casting has greater reliability than static castings. They are relatively free
from gas and shrinkage porosity.
Surface treatments such as case carburizing, flame hardening and have to be used when a
wear resistant surface must be combined with a hard tough exterior surface
One such application is bimetallic pipe consisting of two separate concentric layers of
different alloys/metals bonded together
UNIT II
1. Sketch the overall setup of submerged welding process and explain the working
principle.
Submerged arc welding (SAW) is a
common arc welding process. The first
patent on the submerged-arc welding
(SAW) process was taken out in 1935 and
covered an electric arc beneath a bed of
granulated flux.
the process requires a continuously fed
consumable solid or tubular (metal cored)
electrode.[1] The molten weld and the arc
zone are protected from atmospheric
contamination by being "submerged" under
a blanket of granular fusible flux consisting
of lime, silica, manganese oxide, calcium
fluoride, and other compounds.
When molten, the flux becomes conductive,
and provides a current path between the
electrode and the work. This thick layer of
flux completely covers the molten metal
thus preventing spatter and sparks as well as suppressing the intense ultraviolet radiation
and fumes that are a part of the shielded metal arc welding (SMAW) process.
2. Sketch the three types flames in oxy acetylene welding and state their characteristics.

Neutral

Excess Acetylene (or ”carburizing”)

Oxidizing (or ”excess oxygen” )
The type of flame produced depends upon the ratio of
oxygen to acetylene in the gas mixture which leaves
thetorch tip.
The neutral flame (Fig. 4-1) is produced when the ratio of
oxygen to acetylene, in the mixture leaving the torch,
isalmost exactly one-to-one. It’s termed ”neutral” because it
will usually have no chemical effect on the metal
beingwelded. It will not oxidize the weld metal; it will not
cause an increase in the carbon content of the weld metal.
The excess acetylene flame (Fig. 4-2), as its name implies, is created when the
proportion of acetylene in themixture is higher than that required to produce the neutral
flame. Used on steel, it will cause an increase in thecarbon content of the weld metal.
The oxidizing flame (Fig. 4-3) results from burning a mixture which contains more
oxygen than required for aneutral flame. It will oxidize or ”burn” some of the metal being
welded.
3. Explain plasma arc welding process with neat sketch and explain its advantages.




Construction
Working principle
Advantage
applications
4. Sketch the different types of weld defects and mention how they occur?
5. Explain TIG and MIG welding processes with a neat sketch.
 Electric
arc
produced
between
consumable electrode and work piece.
 Argon or helium gas is used.
 100 A to 400 A.
 Electrode is fed continuously.
 No flux is used.
 High speed welding.
6. Explain resistance spot welding with sketch.

It is used for making lab
joint. Not continuous welding

.025 mm to 1.25 mm
thickness metal sheet can be easily
weld. Max 12 mm thickness.

Metal pieces placed
between copper electrodes.

After heating 2 KN
pressure is applied on joints.

Electrodes are cooled with water to avoid over heating.
7. Describe electron beam welding process with neat sketch.
 Electron
beam is used to weld
work piece.
 Electricall
y heated (vacuum)
tungsten will emit
electron.
 Electron is
passes through anode
hole and focused by
focusing lens.
 Focused
electron beam strikes the
work piece.
 Kinetic energy of electron beam is converted into heat energy.
 Beam dia 0.25 mm to 1 mm. focusing length 40mm for Al 30mm for steel.
8. Describe with neat sketch the components of oxy acetylene gas welding equipment.

Construction

Working principle


Advantage
applications
9. Describe with neat sketches, various steps in friction welding.

Construction

Working principle


Advantage
applications
10. Describe with a neat sketch the principle of percussion welding.

Construction

Working principle


Advantage
applications
11. LASER welding process.
Light energy is
converted into heat energy
 By
exposing
ruby crystal in intense light
flash LASER beam can be
produced.
 LASER beam
is focused by focusing lens to
the work piece in the form of
coherent monochromatic light.
 Heat
is
generated when LASER hits
the work piece, which
sufficient to melt the work
piece.

.
.
UNIT III
1. What is smith forging operation? With neat sketches, explain upsetting bending &
swaging operations.
2. Distinguish between forging hammers and forging presses. Explain the working of drop
hammer with neat sketch.
3. Compare the differences between hot and cold extrusion processes.
Heated billet metal is placed in a press.
The heated billet is pushed by the ram
and with the application of ram pressure
the metal plastically forced through the
die and cut at the die face.
Working material placed between die
and ram.
Sudden impact is given to the ram, the
metal flows plastically in the upward
direction.
4. Explain different types of rolling mills.
It has two rolls.
Both rolls are rotate in a constant direction about
the horizontal axis.
This process reduce the diameter of the stock and
increase its length.
It has three rolls which are rotate in a constant
direction.
The upper and lower mills are drive rolls and
middle roll is rotates by friction.
It is used in reversing mills for the rolling of
hot and cold rolling of sheets.
To avoid the bending of work rolls due to low
strength and rigidity.
The large diameter back up rolls are installed.
The work rolls are supported by back up
rolls.
The work rolls are driven by driving rolls.
5. Explain briefly the wire drawing process.
The diameter less than 16 mm has
drawn in the form of wire coil.
Point of the wire is sized is it is freely
enter into die.
That seized point is fixed on the pliers
which pulls the rod through all the
zones of die orifice.
6. What is shape rolling? Mention the products of shape rolling and explain production of
any one of the product with sketches.
7. Thread rolling process.

Both dies has the thread
profile in its internal diameter.

During rolling process
thread profile is projected on the work
piece surface.
UNIT IV
1. Describe metal spinning process with a neat sketch and state its advantages and specific
uses
Shaping thin
sheets by pressing
them against a
form with a blunt
tool to force the
material into a
desired form
2. Explain hydro forming process with neat sketches. Make a brief comparison of this
process with conventional deep drawing.
3. Sketch and explain the following explosive forming methods:
(a) Confined system
(b) Un confined system
Explosive energy used s metal forming Sheet-metal blank is clamped over a die
Assembly is immersed in a tank with water Rapid conversion of explosive charge into
gas generates a shock wave .the pressure of this wave is sufficient to form sheet metals
4. Distinguish between blanking and punching operations .sketch and explain the elastic
phase , plastic phase and fracture phase that takes place in blanking operation.
5. Briefly explain what are compound dies and progressive dies, with suitable sketches.
6. Explain the three bending methods with suitable sketches.
7. Write short notes on
(b) Magnetic pulse forming
(c) Super plastic forming
8. Describe the shearing and bending operations with suitable examples.
Plastic Deformation: the blade being to undergo elastic deformation
Shear: The begin to penetrate which produces shear of work.
Fracture: fracture line originating from the point of blade and cause separation.
Sheet metal allowed to
passes through the roller.
By adjusting the position of
roller metal sheet can bend
to required radius.
9. Explain with a sketch the principle of stretch forming.
Metal sheet is placed in carriage by using gripping jaw.
Form die having the required external profile is fixed on ram.
By moving ram upward metal sheet is deformed to required shape.
10. Bending using wiping die.
The plastic deformation of
metals about a linear axis
with little or no change in
the surface area.
The purpose of bending is
to form sheet metal along a
straight line
UNIT V
1. Briefly explain the following methods of bonding of thermoplastics
(i) Fusion bonding
(ii) Vibration welding
(iii) Solvent bonding
(iv) Induction welding
2. Describe the following plastic processing methods, with help of neat sketches
(i) Blow moulding
used to make thermoplastic
bottles and hollow sections.
Starting material is a
roundheated solid-bottom
hollow tube – perform.Perform
inserted into two die halves and
air is blown inside to complete
the process
Melting the resin- done in extruder.
Form the molten resin into a cylinder or tube (this tube is called parison).
The parison is placed inside a mold, and inflated so that the plastic is pushed outward
against the cavity wall.
The part is allowed to cool in the mold and is then ejected.
The part is trimmed.
(ii) Compression moulding
The process of
molding a
material in a
confined shape
by applying
pressure and
usuallyheat.
Almost
exclusively for thermoset materials
Used to produce mainly electrical products Thermoset granules are “compressed” in a
heated mold to shape required. Examples: plugs, pot handles, dishware
3. Explain injection moulding process with a neat sketch?
Used to form hollow seamless products such as bins. Molten charge is rotated in a mold
in two perpendicular axes simultaneously, or rotated while tilting.
Most widely used process.Suitable for high production of thermoplastics. Charge fed
from a hopper is heated in a barrel and forced under high pressure into a mold cavity.
Several types. Variety of parts can be made.
4. Explain thermoforming process.
Sheet material heated to
working temperature then
formed into desired shape by
vacuumsuction or pressure.
Suitable for large items such
as bath tubs.
5. Explain transfer moulding process.
A process of forming articles by
fusing a plastic material in a
chamber then forcing thewhole
mass into a hot mold to solidify.
Used to make products such as
electrical wall receptacles and
circuit breakers.
Similar to compression molding
except thermosetting charge is
forced into a heated moldcavity
using a ram or plunger.
6. Compression moulding process.
The process of molding a
material in a confined shape
by applying pressure and
usuallyheat.
Almost exclusively for
thermoset materials.
Used to produce mainly
electrical products.
Thermoset granules are
“compressed” in a heated
mold to shape required.
Examples: plugs, pot handles, dishware.
7. Extrusion process.
Extrusion is the process of squeezing metal in a closed cavity through a tool, known as adie
using either a mechanical or hydraulic press.Similar to injection molding except long uniform
sections are produced –e.g. pipes, rods,profiles.
Extrusion often minimizes the need for secondary machining,and as a result could result
infinancial savings. However extruded objects are not of the same dimensional accuracy or
surfacefinish as machined parts.