QUESTION PAPER CODE : 11517

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2012

MANUFACTURING TECHNOLOGY – I

PART – A

1. What is meant by core print?

2. Name the different melting furnaces employed for metal casting
3. What is meant by ‘carburising flame’ in gas welding?
4. What is the principle of thermit welding?
5. Working on the metal Lead at room temperature , is considered to be hot working. Why?
6. List two advantages of cold extrusion over hot extrusion
7. What is ‘Lancing’ operation that is done on sheet metals?
8. What is the limitations of explosive forming?
9. Name two important difference between thermoplastics and thermosetting plastics
10. What is film blowing?

PART – B

11. a) i) Describe the various pattern allowances which can be quantitatively specified
ii) What are the desirable properties of moulding sand for sand casting? Explaing briefly
each one
Or

b) i) With illustrative sketches, explain the various casing defects indicating, their casues and
remedies.

ii) Explain the stages of preparing shell mould, with suitable sketches. List the unique
advantages of making castings in shell moulds

Steps in shell-molding

Shell-mold casting yields better surface quality and tolerances. The process is
described as follows:
The 2-piece pattern is made of metal (e.g. aluminum 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.

Advantages
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
Can be mechanized for mass production
Disadvantages
More expensive metal pattern
Difficult to justify for small quantities

12. a) i)Discuss the gas welding process and the necessary equipments needed with suitable
sketches

GAS WELDING
 Sound weld is obtained by selecting proper size of flame, filler material and method
of moving torch
 The temperature generated during the process is 33000c.
 When the metal is fused, oxygen from the atmosphere and the torch combines with
molten metal and forms oxides, results defective weld
 Fluxes are added to the welded metal to remove oxides
 Common fluxes used are made of sodium, potassium, Lithium and borax.
 Flux can be applied as paste, powder, liquid. solid coating or gas.
GAS WELDING EQUIPMENT
1. Gas Cylinders
Pressure
Oxygen – 125 kg/cm2
Acetylene – 16 kg/cm2
Regulators
Working pressure of oxygen 1 kg/cm2
Working pressure of acetylene 0.15 kg/cm2
Working pressure varies depends upon the thickness of the work pieces welded.
. Pressure Gauges
. Hoses
. Welding torch
. Check valve
. Non return valve

ii) Explain the metal arc welding process with a neat sketch

Arc welding
Uses an electric arc to coalesce metals
Arc welding is the most common method of welding metals
Electricity travels from electrode to base metal to ground
 Arc welding Equipments
• A welding generator (D.C.) or Transformer (A.C.)
• Two cables- one for work and one for electrode
• Electrode holder
• Electrode
• Protective shield
• Gloves
• Wire brush
• Chipping hammer
• Goggles

Advantages
Most efficient way to join metals
Lowest-cost joining method
Affords lighter weight through better utilization of materials
Joins all commercial metals
Provides design flexibility
Disadvantages
• Manually applied, therefore high labor cost.
• Need high energy causing danger
• Not convenient for disassembly.
• Defects are hard to detect at joints.

Or
b) i) Explain the plasma arc welding process with a neat sketch and list out its advantages

 Special form of GTAW in which a constricted plasma arc is directed at weld area
 Tungsten electrode is contained in a nozzle that focuses a high velocity stream of inert
gas (argon) into arc region to form a high velocity, intensely hot plasma arc stream
 Temperatures in PAW reach 28,000 C (50,000 F), due to constriction of arc,
producing a plasma jet of small diameter and very high energy density

ii) Sketch the different types of weld defects and mention how they occur
Undercuts/Overlaps
• Grain Growth
A wide T will exist between base metal and HAZ. Preheating and cooling methods
will affect the brittleness of the metal in this region
• Blowholes
Are cavities caused by gas entrapment during the solidification of the weld puddle.
Prevented by proper weld technique (even temperature and speed)
• Inclusions
Impurities or foreign substances which are forced into the weld puddle during the
welding process. Has the same effect as a crack. Prevented by proper technique/cleanliness.
 • Segregation
Condition where some regions of the metal are enriched with an alloy ingredient and
others aren‟t. Can be prevented by proper heat treatment and cooling.
• Porosity
The formation of tiny pinholes generated by atmospheric contamination. Prevented by
keeping a protective shield over the molten weld puddle.
13. a) With neat sketches, explain the following smith forging operation
i. Upsetting

Upsetting, or heading, a common technique for making fasteners, gathers steel in the head
and other sections along the length of the part.

ii. Bending

Bending is a manufacturing process that produces a V-shape, U-shape, or channel

shape along a straight axis in ductilematerials, most commonly sheet metal

iii. Swaging

Process that reduces/increases the diameter, tapers, rods or points round bars or tubes by
external hammering

iv. Fullering
 v. Punching and drifting

It is a process of producing holes in motel plate is placed over the hollow cylindrical
die. By pressing the punch over the plate the hole is made.

vi. Edging

Or

b) With suitable sketches, explain the following:

i. Stages involved in “Shape rolling” of structural sections

ii. Cold extrusion forging
iii. Seamless tube drawing
14. a) i) Sketch and explain the following sheet metal bending operations
1. Sheet bending using V-die
2. Bending edge of a sheet using wiping die
3. Roll bending

Bending where plates, sheets and rolled shapes can be bent to a desired curvature Roll
bending toll can bend plate up to 6 inches thickBending a sheet to a round shape using four-slide
machine
Or

B) i) With a neat diagram, explain the principle of explosive forming

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
 ii) Explain the hydro forming process with neat sketches. Make a brief comparison of this process
with conventional deep drawing

The pressure over rubber membrane is controlled throughout the forming cycle ,with
max
pressure up to 100 Mpi
As a result the friction at the punch-cup interface increases, this increase reduces the
longitudinal tensile stresses in the cup and delays fracture

15. A) i) Describe briefly the plunger type injection moulding process for production plastics
components

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.

ii) Explain, with neat diagrams, the thermoforming process. State its advantages over other processes

Sheet material heated to working temperature then formed into desired shape by vacuum
suction or pressure. Suitable for large items such as bath tubs

Or
B)With neat sketches, explain the working principle and applications of the following moulding
processes for plastics:
i. Compression moulding

The process of molding a material in a confined shape by applying pressure and usually
heat.
• 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

ii. Transfer moulding

A process of forming articles by fusing a plastic material in a chamber then forcing the
whole 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
mold
cavity using a ram or plunger.
Examples: electrical switchgear, structural parts