Introduction to Manufacturing Process

1. Ferdous Sarwar, PhD
Assistant Professor
Department of IPE, BUET

2. Manufacturing
Technologically, Manufacturing is the application of physical and
chemical processes to alter the geometry, properties and/or
appearance of a given starting material to make parts or products.
Economically, Manufacturing is the transformation of the material
into items of greater value (Value addition) by means of one or
more processing and/or assembly operations.
Materials in manufacturing:
◙ Metals
◙ Ceramics
◙ Polymers
◙ Composites
Manufacture Two Latin words:
Manus (Hand) & Factus (Make)

3. Manufacturing
Process
Processing Operations Assembly Operations
Surface
Processing
Operations
Property
Enhancing
Processes
Shaping
Process
Permanent
Joining
Mechanical
Fastening
Threaded
fasteners
Permanent
fastening
methods
Adhesive
bonding
Brazing,
Soldering
WeldingHeat
Treatment
Coating &
deposition
processes
Cleaning
& Surface
Treatment
Solidification
processes
Particulate
processes
Deformation
processes
Material
removal
Classification of Manufacturing Process

4. Welding Process
•Welding is a process for joining where two (or more) parts are
coalesced at their contacting surfaces by application of heat and/or
pressure
•Many welding processes are accomplished by heat alone, with no
pressure applied
•Others by a combination of heat and pressure
•Still others by pressure alone with no external heat
•In some welding processes a filler material is added to facilitate
coalescence
Application of Welding:
•Aircraft construction
•Automobile construction
•Building construction
•Bridges
•Pressure vessels and tanks
•Ships
Application of Welding:
•Railroads
•Transformers
•Household or office furniture
•Repair of broken and damaged
components and machinery.

5. Some 50 different types of welding processes have been catalogued by the
American Welding Society (AWS)
Welding processes can be divided into two major categories:
1. Fusion welding:
Joining processes that melt the base metals
In many fusion welding operations, a filler metal is added to the
molten pool to facilitate the process and provide bulk and added
strength to the welded joint
A fusion welding operation in which no filler metal is added is
called an autogenous weld
2. Solid state welding:
Joining processes in which coalescence results from application
of pressure alone or a combination of heat and pressure
If heat is used, temperature is below melting point of metals
being welded
No filler metal is added in solid state welding
Types of Welding

6. Types of Welding
Gas Welding
Air-acetylene Welding
Oxy-hydrogen Welding
Oxy-acetylene Welding
Pressure Gas Welding
Arc Welding
Carbon Arc Welding
Flux Cored Arc Welding
TIG (or GTAW) Welding
Plasma Arc Welding
Shielded Metal Arc Welding
Submerged Arc Welding
MIG (or GMAW) Welding
Electro slag Welding
Stud Arc Welding
Resistance Welding
Spot Welding
Seam Welding
Projection Welding
Resistance Butt Welding
Flash Butt Welding
Percussion Welding
High Frequency Resistance Welding
Solid State Welding
Cold Welding
Explosive Welding
Friction Welding
Roll Welding
Diffusion Welding
Forge Welding
Hot Pressure Welding
Ultrasonic Welding
Thermo-Chemical Welding
Thermit Welding
Atomic Hydrogen Welding
Radiant Energy Welding
Electron Beam Welding
Laser Beam Welding

7. Commonly Welded Base Metals
Metals can be classified as
1. Ferrous 2. Non- Ferrous
Wrought Iron
Cast Iron
Carbon Steel (Low, Medium
and High Carbon Steels)
Cast Steels
Alloy Steels
Stainless Steels
Aluminium and its alloys
Copper and its alloys
Magnesium and its alloys
Nickel and its alloys
Zinc and its alloys, etc

8. Advantages of Welding
A good weld is as strong as the base metal
General welding equipment is not very costly
Portable welding equipments are available
Welding permits considerable freedom in design
A large number of metals/alloys both similar and dissimilar can
be joined by welding.
Welding can join work pieces through spots, as continuous
pressure tight seams, end-to-end and in a number of other
configurations
Welding can be mechanized

9. Disadvantages of Welding
Welding gives out harmful radiations (light), fumes and spatter
Welding results in residual stresses and distortion of the work
pieces
Jigs and fixtures are generally required to hold and position the
parts to be welded
Edge preparation of the work pieces is generally required before
welding them
A skilled welder is a must to produce a good welding job
Welding heat produces metallurgical changes. The structure of the
welded joint is not same as that of the parent metal
A welded joint, for many reasons, needs stress-relief heat treatment

10. Welding as Compared to Casting
 Welding is economical and faster as compared to casting.
Fabricated mild steel structures are lighter and have more tensile
strength as compared to cast iron.
Cost of pattern making and storing is eliminated in welding.
Welding can join dissimilar metals and thus different part of the
structure can be fabricated with different metals.
Welding fabrication involve inventory much less as compared to
casting.
 As compared to casting and riveting fewer persons are involved in a
welding process.
Structural shapes can be easily produced by welding than casting.

11. Welding as Compared to Casting
Casting better than welding
Reducing cost:
•Shortening machining time
•Speeding assembly by reducing the number of individual parts
•When mass production of a part is needed
Adding value
•Company names and logo may be cast into the part -- even your
phone number!

12. Welding as Compared to Riveting

13. Welding as Compared to Riveting
Much faster and economical than riveting
Being noiseless as compared to riveting
Welded pressure vessels are more (fluid and) pressure tight as
compared to riveted ones
Ratio between weight of weld metal and the entire weight of structure
is much lesser than the ratio between the weight of rivets and the entire
weight of the structure
Welding can carried out as any point but riveting need enough
clearance
Layout for punching or drilling of holes is not required in welding
100% efficient joint difficult by riveting

14. Preparation or edge shaping may be applied to
each piece (joint member) in the same way, or
combinations of the joint preparations may be
used. The edge preparation for welding these
joints depends on the strength requirements
and other design considerations.
Edge Preparation
Proper joint design is the key to good weld
design. The loads in a welded-steel design are
transferred from one member to another
through welds placed in weld joints.
Both the type of joint and the type of weld are specified by the designer. So its
important for a designer to know what are the types and edge preparations are
possible in each type of weld.

15. Types of welds
Double fillet tee joint
Inside single fillet
Outside single fillet
Double fillet lap joint
Square groove weld
Single bevel groove weld
Single V-groove weld
Single U-groove weld
single J-groove weld
Double V-groove weld for thicker sections
Plug weld
Slot weld
Fig: Fillet welds
Fig: Groove welds

16. Butt Joints
A butt joint is formed when the pieces to be
welded are laid side by side and it is one of the
most widely used types of joint. The edges of
the butt joint may be prepared for welding as
shown in figure.
Lap Joints
A Lap joint is formed when one piece to be
welded is laid down and another piece is
overlapped to form an edge.
A plug weld is made by welding holes
evenly spaced across the length of one or
both sides of the joint. A slot weld is similar
except slots are made instead of holes.
Types of weld joint
A weld joint is the junction of the edges or
surfaces of parts that have been joined by
welding.
Fig: Butt joint-edge preparation & types of weld
Fig: Lap joint-edge preparation & types of weld

17. T Joints
A T joint is formed when one piece of metal to be welded is
placed vertically on another piece lying horizontally.
The edges of the butt joint may
be prepared for welding as shown
in figure.
Types of weld joint
The vertical member is usually placed at 90 deg to the
horizontal member. One of the most widely used types of
weld applied to a T joint is the fillet weld. When a single
pass or multiple passes are made against the joint, the weld
resembles a Triangle when viewed from the side.
Fig: T joint-edge preparation & types of weld

18. Corner joint
A corner joint is formed by placing one
piece to be welded on the other so that a
corner is formed. The corner may be Flush;
Half Open; or Fully Open.
An edge preparation may be applied to one,
or both of the pieces of the joint for
penetration and strength
Edge joint
An Edge joint is formed when the two
edges of the pieces to be welded come
together. This joint may be formed as a
result of another structural shape and is not
as widely used as some of the other joints.
Types of weld joint
Fig: Edge joint-edge preparation & types of wel
Fig: Corner joint-edge preparation & types of w

19. Welding Filler Metal
 Filter metal/rods is the
material that is added to the
weld pool to assist in filling
the gap (or groove).
 Filler metal forms an integral part of the weld.
 Filler rods have the same or nearly the same chemical composition as the
base metal.
Filler rods are available in a variety of compositions.
[Table 3.3 pp 33]
Filler rod---Size (mm)---Melting point---Flux required---Applications

20. Welding Flux
 During welding, if the metal is heated/melted in air, oxygen from the
air combines with the metal to form oxides which result in poor quality,
low strength welds or, in some cases, may even make welding
impossible.
 A flux is a material used to prevent, dissolve or facilitate removal of
oxides and other undesirable substances.
 A flux prevents the oxidation of molten metal.
 The flux (material) is fusible and non metallic.
 During welding, flux chemically reacts with the oxides and a slag is
formed that floats to and covers the top of the molten puddle of metal
and thus helps keep out atmospheric oxygen and other gases.
Fluxes are available powders, pastes or liquids