This document provides an overview of manufacturing engineering and materials. It begins with definitions of manufacturing and a brief history, including early manufacturing methods dating back 5000-4000 BC using materials like gold, copper, and iron. The industrial revolution marked a transition to mechanized production. A wide variety of metallic and non-metallic materials are now used in manufacturing. The document then discusses different classes of materials like metals, alloys, ceramics, polymers, and composites, providing examples and properties of common materials in each class.

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Manufacturing Engineering &
Materials
BE 101-2
Introduction to Mechanical Engineering Sciences
Module VI
Prepared by:
Mr. Rejeesh C R, Asst. Professor,
Dept. of Mechanical Engineering
Federal Institute of Science and Technology
Introduction
What is Manufacturing?
The word manufacture first appeared in English in 1567 and
is derived from the Latin manu factus, meaning “made by
hand.”
The word manufacturing first appeared in 1683, and the word
production, which is often used interchangeably with the
word manufacturing, first appeared sometime during the 15th
century.
A manufactured item typically starts with raw materials,
which are then subjected to a sequence of processes to make
individual products, it has a certain value.
2
History of Manufacturing
• Manufacturing dates back to the period 5000-4000 B.C.,
and thus, it is older than recorded history, the earliest
forms of which were invented by the Sumerians around
3500 B.C.
• Primitive cave drawings, as well as markings on clay
tablets and stone, needed
(1) some form of a brush and some sort of “paint,” as in the prehistoric
cave paintings in Lascaux, France, estimated to be 16,000 years old;
(2) some means of scratching the clay tablets and baking them, as in
cuneiform scripts and pictograms of 3000 B.C.; and
(3) simple tools for making incisions and carvings on the surfaces of
stone, as in the hieroglyphs in ancient Egypt.
3
History of Manufacturing
• The manufacture of items for specific uses began with the production
of various household artifacts, which were typically made of either
wood, stone, or metal.
• The materials first used in making utensils and ornamental objects
included gold, copper, and iron, followed by silver, lead, tin, bronze
(an alloy of copper and tin), and brass (an alloy of copper and zinc).
• The processing methods first employed involved mostly casting and
hammering, because they were relatively easy to perform. Over the
centuries, these simple processes gradually began to be developed into
more complex operations, at increasing rates of production and higher
levels of product quality.
Note, for example, the lathes for cutting screw threads already were available
during the period from 1600 to 1700, but it was not until some three centuries
later that automatic screw machines were developed.
4
History of Manufacturing
 Although iron making began in the Middle East in about 1100
B.C., a major milestone was the production of steel in Asia
during the period 600-800 A.D.
 A wide variety of materials continually began to be developed.
Today, countless metallic and non-metallic materials with
unique properties are available, including engineered materials
and various advanced materials.
 Among the available materials are industrial or high-tech
ceramics, reinforced plastics, composite materials, and nano-
materials that are now used in an extensive variety of products,
ranging from prosthetic devices and computers to supersonic
aircraft.
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History of Manufacturing
• Until the Industrial Revolution, which began in England in the
1750s and is also called the First Industrial Revolution, goods
had been produced in batches and required much reliance on
manual labour in all phases of their production.
• The Second Industrial Revolution is regarded by some as having
begun in the mid-1900s with the development of solid-state
electronic devices and computers.
• Mechanization began in England and other countries of
Europe, basically with the development of textile machinery and
machine tools for cutting metal. This technology soon moved to
the United States, where it continued to be further developed.
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History of Manufacturing
• A major advance in manufacturing occurred in the early 1800s
with the design, production, and use of interchangeable parts,
conceived by the American manufacturer and inventor Eli
Whitney (1765-1825).
• Prior to the introduction of interchangeable parts, much hand
fitting was necessary because no two parts could be made
exactly alike.
• By contrast, it is now taken for granted that a broken bolt can
easily be replaced with an identical one produced decades after
the original. Further developments soon followed, resulting in
countless consumer and industrial products that we now cannot
imagine being without.
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History of Manufacturing
• Beginning in the early 1940s, several milestones were reached in
all aspects of manufacturing. Note particularly the progress that
has been made during the 20th century, compared with that
achieved during the 40-century period from 4000 B.C. to 1 B.C.
• For eg, in the Roman Empire (~500 B.C. to 476 A.D.), factories
were available for the mass production of glassware; however, the
methods used were generally very slow, and much manpower was
involved in handling the parts and operating the machinery.
Today, production methods have advanced to such an extent that
(a) aluminium beverage cans are made at rates of more than 500 per minute,
with each can costing about four cents to make,
(b) holes in sheet metal are punched at rates of 800 holes per minute, and
(c) incandescent light bulbs are made at rates of more than 2000 bulbs per
minute, each costing less than one dollar.
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Engineering Materials
metals, alloys, composites
• Based on chemical make up and atomic structure, solid
materials have been conveniently grouped into three basic
categories: metals, ceramics and polymers.
• Most materials fall into one distinct grouping or another,
although there are also some intermediates. In addition to these,
there are also three other groups of important engineering
materials: composites, semiconductors and biomaterials.
• There are also advanced materials utilized in high-technology
applications. Recently, a group of new and state of the art
materials called as smart (or intelligent) materials being
developed. Very recently, scientists have developed nano-
engineering materials.
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Engineering Materials
A brief description of the material types and representative
characteristics are: 13
Engineering Materials
Nanomaterials, shape-memory alloys, superconductors, …
Ferrous metals: carbon steels, alloy steels, stainless steels,
tool steels and die steels
Non-ferrous metals: aluminum, magnesium, copper, nickel,
titanium, superalloys, refractory metals,
beryllium, zirconium, low-melting alloys,
gold, silver, platinum, …
Plastics: thermoplastics (acrylic, nylon, polyethylene, ABS,…)
thermosets (epoxies, Polymides, Phenolics, …)
elastomers (rubbers, silicones, polyurethanes, …)
Ceramics: Glasses, Graphite, Diamond, Cubic Boron Nitride
Composites: reinforced plastics, metal-, ceramic matrix composites
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Metals and Alloys
• True metals are pure elements, while alloys are blends of two or
more metals that have been melted together.
• Metallic materials have large number of non localized electrons,
i.e. electrons are not bound to particular atoms. Many properties
of metals are directly attributable to these electrons. (Conductivity)
• All metals are characterized by metallic properties, e.g. lustre,
opacity, malleability, ductility and electrical conductivity.
• Although metals compose about 3/4th of the known elements but
few find service in their pure form. The desired properties for
engineering purposes are often found in alloys.
• Typical examples of metallic materials are iron, aluminium,
copper, zinc, etc. and their alloys. They can be used either in bulk
or powder form.
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Metals and Alloys
• Metals are extremely good conductors of electricity and heat are
not transparent to visible light; a polished metal surface has a
lustrous appearance. Moreover, metals are quite strong, yet
deformable, which accounts for their extensive use in structural
applications.
• Metallic materials are always crystalline in nature. Scientists
have developed amorphous (non-crystalline) alloys by very rapid
cooling of a melt or by very high-energy mechanical milling.
• Recently, scientists have developed materials through rapid
solidification called as quasi-crystals. These are neither
crystalline nor amorphous, but form an ordered structure
somewhere between two known structures. These materials are
expected to exhibit far reaching electrical properties.
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Metals
• Ferrous Metals
– Cast irons
– Steels
• Super alloys
– Iron-based
– Nickel-based
– Cobalt-based
• Non-ferrous metals
– Aluminum and its alloys
– Copper and its alloys
– Magnesium and its alloys
– Nickel and its alloys
– Titanium and its alloys
– Zinc and its alloys
– Lead & Tin
– Refractory metals
– Precious metals
Metals used in manufacturing are usually alloys, which are
composed of two or more elements, with at least one being a
metallic element. Metals and alloys can be divided into two basic
groups: (1) ferrous and (2) nonferrous.
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Metals
• Ferrous metals are based on iron; the group includes steel and
cast iron. Pure iron has limited commercial use, but when
alloyed with carbon, it has greater commercial value than any
other metal.
• Alloys of iron and carbon form steel and cast iron. Steel can be
defined as an iron–carbon alloy containing 0.02% to 2.11%
carbon. It is the most important category within the ferrous metal
group.
• Its composition often includes other alloying elements as well,
such as manganese, chromium, nickel, and molybdenum, to
enhance the properties of the metal.
• Applications of steel include construction (bridges, I-beams, and
nails), transportation (trucks, rails, and rolling stock for railroads),
and consumer products (automobiles and appliances).
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Metals
• Cast iron is an alloy of iron and carbon (2% to 4%) used in
casting (primarily sand casting). Silicon is also present in the
alloy (in amounts from 0.5% to 3%), and other elements are often
added also, to obtain desirable properties in the cast part.
• Cast iron is available in several different forms, of which grey
cast iron is the most common; its applications include blocks and
heads for internal combustion engines.
• Nonferrous metals include the other metallic elements and their
alloys. In almost all cases, the alloys are more important
commercially than the pure metals.
• The nonferrous metals include the pure metals and alloys of
aluminium, copper, gold, magnesium, nickel, silver, tin, titanium,
zinc, and other metals.
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General Properties and
Applications of Ferrous Alloys
• Ferrous alloys are useful metals in terms of
mechanical, physical and chemical properties.
• Alloys contain iron as their base metal.
• Carbon steels are least expensive of all metals while
stainless steels are costly.
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Carbon and alloy steels
Carbon steels
• Classified as low, medium and high:
1. Low-carbon steel or mild steel, < 0.3%C, bolts, nuts and
sheet plates.
2. Medium-carbon steel, 0.3% ~ 0.6%C, machinery,
automotive and agricultural equipment.
3. High-carbon steel, > 0.60% C, springs, cutlery, cable.
Alloy steels
• Steels containing significant amounts of alloying elements.
• Structural-grade alloy steels used for construction industries
due to high strength.
• Other alloy steels are used for its strength, hardness, resistance
to creep and fatigue, and toughness.
• It may heat treated to obtain the desired properties.
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High-strength low-alloy steels (HSLA)
• It is a type of alloy steel that provides better mechanical
properties like improved strength-to-weight ratio or greater
resistance to corrosion than carbon steel.
• HSLA steels vary from other steels in that they are not made
to meet a specific chemical composition but rather to
specific mechanical properties.
• Used in automobile bodies to reduce weight and in
agricultural equipment.
• Some examples are:
1. Dual-phase steels
2. Micro alloyed steels
3. Nano-alloyed steels
22
Stainless Steels
• Characterized by their corrosion resistance, high strength
and ductility, and high chromium content.
• Stainless as a film of chromium oxide protects the metal
from corrosion.
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Stainless steels
• Five types of stainless steels:
1. Austenitic steels
2. Ferritic steels
3. Martensitic steels
4. Precipitation-hardening (PH) steels
5. Duplex-structure steels
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Tool and die steels
• Tool steel is a type of carbon alloy steel that is well-
matched for tool manufacturing, such as hand tools or
machine dies.
• Hardness and ability to retain shape at increased
temperatures are the key properties of this material.
Designed for high strength, impact toughness, and wear
resistance at a range of temperatures.
• The presence of carbides in their matrix plays the dominant
role in the qualities of tool steel. The four major alloying
elements in tool steel that form carbides are: tungsten,
chromium, vanadium and molybdenum.
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Tool and die steels
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Aluminium and aluminium alloys
• Factors for selecting are:
1. High strength to weight ratio.
2. Resistance to corrosion.
3. High thermal and electrical conductivity.
4. Ease of machinability.
5. Non-magnetic.
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Magnesium and Magnesium alloys
• Magnesium (Mg) is the lightest metal.
• Alloys are used in structural and non-structural applications.
• Typical uses of magnesium alloys are aircraft and missile
components.
• Also has good vibration-damping characteristics.
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Copper and Copper alloys
 Copper alloys are metal alloys that have copper as their
principal component. They have high resistance against
corrosion.
 The best known traditional types are bronze, where tin is
a significant addition, and brass, using zinc instead.
 Copper alloys have electrical and mechanical
properties, corrosion resistance, thermal conductivity
and wear resistance.
 Applications are electronic components, springs and
heat exchangers.
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Nickel and Nickel alloys
• Nickel alloys are used extensively because of their corrosion
resistance, high temperature strength and their special magnetic
and thermal expansion properties.
• Used in stainless steels and nickel-base alloys.
• Alloys are used for high temperature applications, such as jet-
engine components and rockets.
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Superalloys
• A super-alloy, or high-performance alloy, is an alloy that
exhibits several key characteristics like excellent mechanical
strength, resistance to thermal deformation, good surface stability
and resistance to corrosion or oxidation.
• The crystal structure is typically face centered cubic austenitic.
Superalloys are high-temperature alloys use in jet engines, gas
turbines and reciprocating engines.
• Inconel is a family of austenite nickel-chromium based super
alloys.
• The main alloying ingredient is nickel in hastelloy. Other alloying
ingredients added are varying percentages of elements of
molybdenum, chromium, iron, manganese, cobalt,
copper, titanium, zirconium, aluminium, carbon, and tungsten.
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Superalloys
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Titanium and Titanium alloys
• Titanium (Ti) is expensive, has high strength-to-weight ratio and
corrosion resistance.
• Used as components for aircrafts, jet-engines, racing-cars and
marine crafts.
33
Other nonferrous metals
1. Beryllium
2. Zirconium
3. Low-melting-point metals:
- Lead
- Zinc
- Tin
4. Precious metals:
- Gold
- Silver
- Platinum
34
Refractory metals
• Refractory metals have a high melting point and retain
their strength at elevated temperatures.
• Applications are electronics, nuclear power and chemical
industries.
• Molybdenum, columbium, tungsten and tantalum are
referred to as refractory metal.
1. Shape-memory alloys (i.e. eyeglass frame, helical spring)
2. Amorphous alloys (Metallic Glass)
3. Nanomaterials
4. Metal foams
Special Metals and Alloys
35
Classification of Ceramics
• Traditional ceramics
– clays: kaolinite
– silica: quartz, sandstone
– alumina
– silicon carbide
• New ceramics
– oxide ceramics : alumina
– carbides : silicon carbide, titanium carbide, etc.
– nitrides : silicon nitride, boron nitride, etc.
• Glass products
– window glass, containers
– light bulb glass, laboratory glass
– glass fibers
– optical glass
• Glass ceramics - polycrystalline structure
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Classification of Polymers
• Thermoplastics - reversible in phase by heating and cooling.
Solid phase at room temperature and liquid phase at elevated
temperature.
• Thermosets - irreversible in phase by heating and cooling.
Change to liquid phase when heated, then follow with an
irreversible exothermic chemical reaction. Remain in solid
phase subsequently.
• Elastomers – Rubbers
Characteristics of Plastics are:
 immune to corrosion
 Good insulator
 unsuitable for higher temperatures
 to improve their properties additives are added.
37
Thermosets
• A thermosetting plastic, also known as a thermoset, is
polymer material that irreversibly cures. The cure may be
done through heat (generally above 2000C), through a
chemical reaction (epoxy, for example).
 Amino resins, Epoxies
 Phenolics, Polyesters, Polyurethanes
 Silicones
 Thermosets are usually liquid or malleable prior to curing
and designed to be molded in to their final form, or used as
adhesives. Others are solids like that of the molding
compound used in semiconductors & integrated circuits.
 Once hardened, a thermoset resin cannot be reheated and
melted back to a liquid form.
38
Thermoplastics
• Thermoplastics, also known as a thermosoftening plastic
is a polymer that turns to a liquid when heated and freezes
to a very glassy state when cooled sufficiently.
• Thermoplastic polymers differ from thermosetting
polymers in that they can be remelted and remoulded.
– Acetals, Acrylics - PMMA
– Acrylonitrile-Butadiene-Styrene - ABS
– Cellulosics, Fluoropolymers - PTFE , Teflon
– Polyamides (PA) - Nylons, Kevlar
– Polysters – PET, Polyethylene (PE) - HDPE, LDPE
– Polypropylene (PP), Polystyrene (PS)
– Polyvinyl chloride (PVC)
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Elastomers
Characteristics of Rubber are
 rough, elastic material
 unaffected by water
 attacked by oil and steam
 Usage: gaskets, flexible couplings, vibration mount
 Natural rubber
 Different Synthetic rubbers
– butadiene rubber, butyl rubber, styrene-butadiene rubber
– chloroprene rubber, ethylene-propylene rubber
– isoprene rubber, nitrile rubber
– Polyurethanes, silicones, thermoplastic elastomers 40
What is a composite Material?
41
Wood is a good example of a natural composite, combination
of cellulose fiber and lignin. The cellulose fiber provides
strength and the lignin is the "glue" that bonds and stabilizes
the fiber.
Bamboo is a very efficient wood composite structure. The
components are cellulose and lignin, as in all other wood,
however bamboo is hollow. This results in a very light yet stiff
structure. Composite fishing poles and golf club shafts copy this
natural design.
The ancient Egyptians manufactured composites!!! Adobe
bricks are a good example. The combination of mud and straw
forms a composite that is stronger than either the mud or the
straw by itself.
Composite Material Defined
Two or more chemically distinct materials which when
combined have improved properties over the individual
materials. Composites could be natural or synthetic.
―A composite material is composed of two or more physically
distinct phases/materials whose combination produces
aggregate properties that are different from those of its
constituents‖
Examples:
– Cemented carbides (WC with Co binder)
– Plastic molding compounds containing fillers
– Rubber mixed with carbon black
– Wood (a natural composite)
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Why Composites are Important
 Composites can be very strong and stiff, yet very light in
weight, so strength-to-weight ratio and stiffness-to-weight
ratio are several times greater than steel or aluminum.
 Fatigue properties are generally better than for common
engineering metals.
 Toughness is often greater too
 Composites can be designed that do not corrode like steel
 Possible to achieve combinations of properties not
attainable with metals, ceramics, or polymers alone.
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Components of composite materials
44
Composites are combinations of two materials in which one of
the material is called the reinforcing phase, is in the form of
fibers, sheets, or particles, and is embedded in the other material
called the matrix phase.
Typically, reinforcing materials are strong with low densities
while the matrix is a ductile/tough material. When a composite
designed and fabricated correctly, it combines the strength of
reinforcement with the toughness of matrix to achieve a
combination of desirable properties not available in a single
conventional material.
Reinforcement: fibers
Carbon, Boron, Organic,
Glass, Ceramic, Metallic
Matrix materials
Polymers, Metals,
Ceramics
Interface
Bonding surface
The Reinforcing Phase
 Function is to reinforce the matrix phase
 Imbedded phase is most commonly one of the following shapes:
 Fibers
 Particles
 Flakes
 In addition, the secondary phase can take the form of an
infiltrated phase in a skeletal or porous matrix
 Example: a powder metallurgy part infiltrated with polymer
45
Fig: Possible physical shapes of imbedded phases in
composite materials: (a) fiber, (b) particle, (c) flake
Composite Structures
 Laminar composite structure – conventional
 Sandwich structure
 Honeycomb sandwich structure
46
Consists of a relatively thick core of low density foam
bonded on both faces to thin sheets of a different material.
Fig: Laminar composite
structures: (b) sandwich structure
using foam core
47
Sandwich Structure – Foam Core
 An alternative to foam core
 Either foam or honeycomb achieves high
strength -to - weight and stiffness - to - weight ratios
Fig: Laminar composite structures:
(c) sandwich structure using
honeycomb core
48
Sandwich Structure –
Honeycomb Core

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Classification Scheme for Composites
1. Metal Matrix Composites (MMCs) - mixtures of ceramics
and metals, such as cemented carbides and other cermets
2. Ceramic Matrix Composites (CMCs) - Al2O3 and SiC
imbedded with fibers to improve properties, especially in
high temperature applications
– The least common composite matrix
3. Polymer Matrix Composites (PMCs) - thermosetting resins
are widely used in PMCs
– Examples: epoxy and polyester with fiber reinforcement, and
phenolic with powders
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Advantages of Composites
50
Higher Specific Strength (strength-to-weight ratio)
Composites have a higher specific strength than many other
materials. A distinct advantage of composites over other
materials is the ability to use many combinations of resins
and reinforcements, and therefore custom tailor the
mechanical and physical properties of a structure.
Corrosion Resistance
Composites products provide long-term resistance to severe
chemical and temperature environments. Composites are the
material of choice for outdoor exposure, chemical handling
applications, and severe environment service.
Advantages of Composites
51
Design flexibility
Composites have an advantage over other materials because
they can be molded into complex shapes at relatively low
cost. This gives designers the freedom to create any shape or
configuration. Boats are a good example of the success of
composites.
Low Relative Investment
One reason the composites industry has been successful is
because of the low relative investment in setting-up a
composites manufacturing facility. This has resulted in many
creative and innovative companies in the field.
Advantages of Composites
52
Durability
Composite products and structures have an exceedingly long
life span. Coupled with low maintenance requirements, the
longevity of composites is a benefit in critical applications. In
a half-century of composites development, well-designed
composite structures have yet to wear out.
In 1947 the U.S. Coast Guard built a series of forty-foot patrol
boats, using polyester resin and glass fiber. These boats were used
until the early 1970’s when they were decommissioned because the
design was outdated. Extensive testing was done on the laminates
after decommissioning, and it was found that only 2-3% of the
original strength was lost after twenty-five years of hard service.
Disadvantages of Composites
53
 Composites are heterogeneous
Properties in composites vary from point to point in the
material. Most engineering structural materials are
homogeneous.
 Many of the polymer based composites are subject to
attack by chemicals or solvents, just as the polymers
themselves are susceptible to attack.
 Composite materials are generally expensive.
 Manufacturing methods for shaping composite materials
are often slow and costly.
Disadvantages of Composites
54
 Composites are highly anisotropic
The strength in composites vary as the direction along
which we measure changes (most engineering structural
materials are isotropic).
As a result, all other properties such as, stiffness, thermal
expansion, thermal and electrical conductivity and creep
resistance are also anisotropic.
The relationship between stress and strain (force and
deformation) is much more complicated than in isotropic
materials.
The experience and intuition gained over the years about the
behavior of metallic materials does not apply to composite materials.

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Disadvantages of Composites
55
 Composites materials are difficult to inspect with conventional
ultrasonic, eddy current and visual NDI methods such as
radiography.
American Airlines Flight 587, broke apart over New York on Nov.
12, 2001 (265 people died). Airbus A300’s 27-foot-high tail fin
tore off. Much of the tail fin, including the so-called tongues that
fit in grooves on the fuselage and
connect the tail to the jet, were
made of a graphite composite.
The plane crashed because of
damage at the base of the tail that
had gone undetected despite
routine nondestructive testing and
visual inspections.
The Crystal Structure of Metals
 When metals solidify from a molten state, the atoms
arrange themselves into various orderly
configurations, called crystals; this atomic
arrangement is called crystal structure or crystalline
structure.
 The smallest group of atoms showing the
characteristic lattice structure of a particular metal is
known as a unit cell. It is the building block of a
crystal, and a single crystal can have many unit cells.
56
The Crystal Structure of Metals
The following are the four basic atomic arrangements in metals:
l. Simple cubic (SC); examples: alpha - polonium
2. Body-centered cubic (bcc); examples: alpha iron, chromium,
molybdenum, tantalum, tungsten, and vanadium.
3. Face-centered cubic (fcc); examples: gamma iron, aluminium,
copper, nickel, lead, silver, gold, and platinum.
4. Hexagonal close-packed (hcp); examples: beryllium, cadmium,
cobalt, magnesium, alpha titanium, zinc, and zirconium.
• These structures when represented in illustrations; each sphere
represents an atom. The distance between the atoms in these
crystal structures is on the order of 0.1 nm.
57
Simple Cubic
Fig The Simple cubic (sc) crystal structure: (a) hard-ball model; (b)
unit cell;
• Each layer is stacked on the previous layer perfectly.
• There are 8 eighths (one in each corner) for a total
of ONE atom in the unit cell.
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Coordination Number
• CN, the coordination number, which is the number of
closest neighbours to which an atom is bonded.
59 5
Atomic Packing Factor
(No. of atoms/unit cell) X volume of each atom
Volume of unit cell
APF =
In crystallography, atomic packing factor (APF), packing
efficiency is the fraction of volume in a crystal structure that
is occupied by constituent particles. It is dimensionless and
always less than unity.
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4
• Rare due to poor packing (only Po has this structure)
• Close-packed directions are cube edges.
• Coordination # = 6
(# nearest neighbors)
Simple Cubic Structure (SC)
APF for a simple cubic
structure = 0.52
61
Body-Centered Cubic Crystal Structure
Fig The body-centered cubic (bcc) crystal structure: (a) hard-ball model;
(b) unit cell;
• Each layer is offset from the layer before. Arrangements duplicate
themselves every other layer.
• There are 8 eights (one in each corner) and one full atom in the centre
for a total of Two atoms in the unit cell.
62
a
R
9
• APF for a body-centered cubic structure = 0.68
Unit cell contains:
1 + 8 x 1/8
= 2 atoms/unit cell
Atomic Packing Factor: BCC
• Coordination # = 8
63
Face-Centered Cubic Crystal Structure
Fig: The face-centered cubic (fcc) crystal structure: (a) hard-ball model;
(b) unit cell;
• Each layer is offset from the layer before. Arrangements
duplicate themselves every third layer.
• There are 8 eighths (one in each corner), and 6 halves (one
on each face of the cube) for a total of Four atoms in the unit
cell.
64
Unit cell contains:
6 x 1/2 + 8 x 1/8
= 4 atoms/unit cell
a
7
• APF for a body-centered cubic structure = 0.74
Atomic Packing Factor: FCC
Coordination # = 12
65
Hexagonal Close Packed Crystal Structure
Fig: The hexagonal close-packed (hcp) crystal structure: (a) unit
cell; and (b) single crystal with many unit cells.
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• Coordination # = 12
Number of atoms per unit cell :
12 (corner atoms) x 1/6 + 3 (interior atoms) + 2
(face atoms) x 1/2= 6 atoms / unit cell
• APF = 0.74
Hexagonal Close-packed Structure
(HCP)
67
Definition of Heat Treatment
Heat treatment is an operation or combination of
operations involving heating at a specific rate,
soaking at a temperature for a period of time and
cooling at some specified rate.
The aim is to obtain a desired microstructure to
achieve certain predetermined properties (physical,
mechanical, magnetic or electrical).
68
Objectives of Heat Treatment Processes
The major objectives are
• to increase strength, hardness and wear resistance
(hardening)
• to increase ductility, toughness and softness (tempering,
annealing)
• to obtain fine grain size (annealing, normalising)
• to remove internal stresses induced by differential
deformation by cold working, non-uniform cooling from
high temperature during casting and welding (stress
relief annealing)
69
• to improve machinability (annealing and normalizing)
• to improve cutting properties of tool steels (hardening
and tempering)
• to improve surface properties (surface hardening,
corrosion resistance-stabilizing treatment and surface
treatment)
• to improve electrical properties (recrystallization,
tempering, age hardening)
• to improve magnetic properties (hardening, phase
transformation)
70
Objectives of Heat Treatment Processes
Annealing
• It alters the physical and chemical properties of a material to
increase its ductility and reduce its hardness, making it more
workable.
• It involves heating of material above recrystallization
temperature, maintaining it for some time and then cooling.
• In the cases of copper, steel, silver and brass, this process is
performed by heating the material (until glowing) for a while and
then slowly cooling to room temperature in still air.
• Copper, silver and brass can be cooled slowly in air, or quickly
by quenching in water, unlike ferrous metals, such as steel, which
must be cooled slowly to anneal.
• In this fashion, the metal is softened and prepared for further
work -- such as shaping, stamping, or forming.
71
Hardening
• Hardening is used to increase the hardness of a metal. A
harder metal will have a higher resistance to plastic
deformation than a less hard metal.
• Hardening is a form of heat treatment in which a metal
part is heated and then quenched. The quenched metal
undergoes a martensitic transformation, increasing the
hardness and brittleness of the part.
• Martensitic transformation, is a hardening mechanism specific for steel. The steel must be
heated to a temperature where the iron phase changes from ferrite into austenite, i.e. changes
crystal structure from BCC to FCC.
• In austenitic form, steel can dissolve more carbon. Once the carbon has been dissolved, the
material is then quenched with a high cooling rate so that the carbon does not have time to form
precipitates of carbides. When the temperature is low enough, the steel tries to return to the low
temperature crystal structure BCC. This change is very quick and is called a martensitic
transformation. This phase is called martensite, and is extremely hard.
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Quenching
• Quenching is the rapid cooling of a work piece to obtain
favourable material properties… For instance, it can
reduce crystallinity and thereby increase the hardness of
both alloys and plastics.
• It is commonly used to harden steel by
introducing martensite, in which case the steel must be
rapidly cooled, the temperature at which austenite becomes
unstable.
• Extremely rapid cooling can prevent the formation of crystal
structure, resulting in amorphous metal or "metallic glass".
• If the percentage of carbon is less than 0.4 %, quenching is
not possible.
73
Tempering
• Tempering is used to increase the toughness of iron-
based alloys.
• Tempering is usually performed after hardening, to reduce
some of the excess hardness, and is done by heating the
metal to some temperature below the critical point for a
certain period of time, then allowing it to cool in still air.
• The exact temperature determines the amount of hardness
removed, and depends on both the composition of the alloy
and on the desired properties in the finished product.
• For instance, very hard tools are often tempered at low
temperatures, while springs are tempered to much higher
temperatures.
74
Normalizing
• Normalizing is for making the material softer but does not
produce the uniform material properties of annealing.
• A material can be normalized by heating it to a specific
temperature and then letting the material cool to room
temperature outside of the oven.
• Normalising refines the grain size, improves the uniformity
of microstructure and properties of hot rolled steel.
• Normalizing is used in some plate mills, in the production
of large forgings such as railroad wheels and axles, some
bar products. This process is less expensive than
annealing.
75
Carburizing
• In carburization iron or steel absorbs carbon, when the
metal is heated in the presence of carbon bearing materials
like charcoal or carbon monoxide, with the intent of
making the metal harder.
• Depending on the amount of time and temperature, the
affected area can vary in carbon content. Longer
carburizing times and higher temperatures typically increase
the depth of carbon diffusion.
• When the iron or steel is cooled rapidly by quenching, the
higher carbon content on the outer surface becomes hard via
the transformation from austenite to martensite, while the
core remains soft and tough as a ferritic and/or pearlite
microstructure.
76
Carburizing
• This manufacturing process can be characterized by the
following key points:
 It is applied to low-carbon work pieces;
 work pieces are in contact with a high-carbon gas, liquid or
solid;
 it produces a hard work piece surface;
 work piece cores largely retain their toughness and ductility;
 it produces case hardness depths of up to 0.25 inches (6.4 mm).
• In some cases it serves as a remedy for undesired
decarburization that happened earlier in a manufacturing
process.
77
Properties of materials
Mechanical properties of materials
Strength, Toughness, Hardness, Ductility,
Elasticity, Fatigue and Creep
Chemical properties
Oxidation, Corrosion, Flammability, Toxicity, …
Physical properties
Density, Specific heat, Melting and boiling point,
Thermal expansion and conductivity,
Electrical and magnetic properties
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Mechanical Properties
• Subgroup of physical properties.
• response to force or stress
– force – a push or pull
– stress – force causing a deformation or distortion
(force per unit area)
Stress is the applied force or system of forces that tends to
deform a body. From the perspective of what is happening
within a material, stress is the internal distribution of forces
within a body that balance and react to the loads applied to
it.
79 80
Types of Stresses
Tension Compression
TorsionShear
Mechanical Properties Examples
• Workability
– malleability – can be flattened
– ductility – can be drawn into wire (stretched), bent,
or extruded
• Brittleness - breaks instead of deforming when stress is
applied
81
• elasticity
– ability to return to original shape after being deformed by
stress
– rubber ball or piece of elastic
• plasticity
– retains new shape after being deformed by stress
– wet clay ball or piece of saran wrap
Mechanical Properties Examples
82
• hardness
– resistance to denting or scratching
– Brinell Hardness, Vickers hardness and Rockwell
test are used to measure hardness.
Mechanical Properties Examples
83
Mechanical Properties Examples
• Strength is the ability of a material to resist deformation.
The strength of a component is usually considered based on
the maximum load that can be borne before failure.
• Toughness is the ability of a material to absorb energy and
plastically deform without fracturing.
Impact strength is the ability to withstand sudden impact without
fracture.
• Impact strength/Toughness –- Charpy test, IZOD test.
• Universal testing machine is used to find compressive
strength, tensile strength and bending strength.
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Mechanical Properties Examples
• Fatigue is the phenomenon of sudden fracture of a component
after a period of cyclic loading in the elastic regime. Failure is
the end result of a process involving initiation and growth of a
crack, usually at the site of stress concentration on the surface.
Eventually after reaching a critical size, the crack will
propagate suddenly, and the structure will fracture.
• Creep (cold flow) is the tendency of a material to deform
permanently under the influence of mechanical stresses. It can
occur as a result of long-term exposure to high levels of stress
that are still below the yield strength of the material.
A yield strength of a material is defined as the stress at which
a material begins to deform plastically. Prior to the yield point the
material will deform elastically and will return to its original shape
when the applied stress is removed.
85
Methods of Manufacturing
1. Shaping processes
Casting, forging, rolling etc..
2. Machining processes
Turning, Milling, drilling, grinding etc..
3. Joining processes
Welding, soldering, riveting etc..
86
Moulding
Mould
A mould is a cavity or void made in a compact sand mass,
which when filled molten metal, will produce a casting of the
desired shape.
The mould made in the sand is known as sand mould.
The process of producing a mould or cavity in the sand is
called moulding.
A casting can be defined as a molten material that has
been poured into a prepared cavity and allowed to
solidify.
Casting
Sand Casting
Making of castings in moulds of sand or similar
material.
The principal metals used are cast irons and
steel, brass and other copper alloys, aluminium
and magnesium alloys.
The softer alloys of lead, tin etc. are usually cast
in steel moulds or dies.
The principal raw material used in moulding.
The sand in moulding is silica, the oxide of silica.
The factors to be controlled in the preparation of
sand for making moulds are clay content,
moisture content, grain size permeability, and
strength of the sand.
Moulding Sand
89
Green sand
It is moist sand containing about 5% moisture. Moulds and
cores may be made from green sand.
 Both moulds and cores may be baked to drive out the
moisture.
 However, the most commonly used moulds are of that is not
dried. They are called green sand moulds.
The moisture content and permeability may be closely
controlled to prevent the trapping of gases which could cause
voids in the casting.
Green sand moulds are those sand moulds, in which
moisture is present in the sand at the time of pouring the
molten metal.
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Main Constituents of Mould Sand
• Silica sand Binder
• Additives Water
Binder impart sufficient strength and cohesiveness to the
moulding sand so as to retain its shape after the mould has
been rammed and the pattern withdrawn.
Additives are added to the moulding sand to improve upon
some of its existing properties or to impart new properties to
it.
Water content is mainly responsible for enabling the clay to
impart the desired strength to the sand.
91
Green-Sand Moulding
The sand is mixed with water and suitable
proportions of bonding agents, as this mixture, in wet
(or “green”) state, is used for making the moulds.
 The mould is prepared in the usual manner. Molten
metal is poured into the mould through the runner.
There is no need of baking the mould before pouring.
Most of the small and medium sized castings,
particularly non-ferrous ones, are made by green-sand
moulding.
92
Advantages of Casting
Complicated shapes can be obtained in quantities at low
cost.
Within certain limits the units are identical in size and
properties.
Replacement can be quickly obtained, provided the pattern
is kept safe.
Certain castings, being solid integral units, are more rigid
than built up units.
Cast metals and alloys, in general, resist creep under high
temperature conditions better than the wrought product.
Steps in making a Casting
• The making of a pattern, which may be in exactly the
same form as the finished product
• The actual making of the mould in sand.
• The pouring into the mould of molten metal, which is
allowed to solidify.
• The removal of casting from the sand, and its cleaning
by removing all superfluous adherent metal a process
called dressing or fettling.
94
Properties of Moulding Sands
 Permeability
 Cohesiveness
 Adhesiveness
 Plasticity
 Refractoriness
95
Making a Sand Mould
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Core and Core Prints
• Castings are often required to have holes, recesses, etc. of
various sizes and shapes. These impressions can be obtained by
using cores.
• So where core is required, provision should be made to support
the core inside the mold cavity. Core prints are used to serve this
purpose.
• The core print is an added projection on the pattern and it forms
a seat in the mold on which the sand core rests during pouring of
the mold.
• The core print must be of adequate size and shape so that it can
support the weight of the core during the casting operation.
• Depending upon the requirement a core can be placed
horizontal, vertical and can be hanged inside the mold cavity.
97
Pattern having core prints.
98
Pattern Making:
 A Pattern is a model or the replica of the object to
be cast.
 Except for the various allowances a pattern exactly
resembles the casting to be made.
 A pattern is required even if one object has to be
cast.
99
Pattern Allowances:
A pattern is larger in size as compared to the final
casting, because it carries certain allowances due to
metallurgical and mechanical reasons for example,
shrinkage allowance is the result of metallurgical
phenomenon where as machining, draft, distortion,
shake and other allowances are provided on the
patterns because of mechanical reasons.
100
Types of Pattern Allowances:
The various pattern allowances are:
1. shrinkage or contraction allowance.
2. Machining or finish allowance.
3. Draft or tapper allowances.
4. Distortion or camber allowance.
5. Shake or rapping allowance.
101
1. Shrinkage Allowance:
All most all cast metals shrink or contract volumetrically on cooling.
The metal shrinkage is of two types:
1. Liquid Shrinkage:
It refers to the reduction in volume when the metal changes from liquid
state to solid state at the solidus temperature. To account for this
shrinkage; riser, which feed the liquid metal to the casting, are
provided in the mold.
2. Solid Shrinkage:
It refers to the reduction in volume caused when metal loses
temperature in solid state. To account for this, shrinkage allowance is
provided on the patterns.
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 Almost all cast metals shrink or contract volumetrically
after solidification and therefore the pattern to obtain a
particular sized casting is made oversize by an amount
equal to that of shrinkage or contraction.
 Different metals shrink at different rates because shrinkage
is the property of the cast metal/alloy.
 The metal shrinkage depends upon:
1. The cast metal or alloy.
2. Pouring temp. of the metal/alloy.
3. Casted dimensions(size).
4. Casting design aspects.
5. Molding conditions(i.e., mould materials and molding
methods employed)
103
Rate of Contraction of Various Metals :
Material Dimension Shrinkage allowance
(inch/ft)
Grey Cast Iron
Up to 2 feet
2 feet to 4 feet
over 4 feet
0.125
0.105
0.083
Cast Steel
Up to 2 feet
2 feet to 6 feet
over 6 feet
0.251
0.191
0.155
Aluminum
Up to 4 feet
4 feet to 6 feet
over 6 feet
0.155
0.143
0.125
Magnesium
Up to 4 feet
Over 4 feet
0.173
0.155
104
2. Machining Allowance:
A Casting is given an allowance for machining, because:
i. Castings get oxidized in the mold and during heat treatment; scales etc.,
thus formed need to be removed.
ii. It is the intended to remove surface roughness and other imperfections
from the castings.
iii. It is required to achieve exact casting dimensions.
iv. Surface finish is required on the casting.
How much extra metal or how much machining allowance
should be provided, depends on the factors listed below:
i. Nature of metals.
ii. Size and shape of casting.
iii. The type of machining operations to be employed for cleaning the
casting.
iv. Casting conditions.
v. Molding process employed
105
Machining Allowances of
Various Metals:
Metal Dimension (inch) Allowance (inch)
Cast iron
Up to 12
12 to 20
20 to 40
0.12
0.20
0.25
Cast steel
Up to 6
6 to 20
20 to 40
0.12
0.25
0.30
Non ferrous
Up to 8
8 to 12
12 to 40
0.09
0.12
0.16
106
3. Draft or Taper Allowance:
 It is given to all surfaces perpendicular to parting line.
 Draft allowance is given so that the pattern can be easily
removed from the molding material tightly packed around
it with out damaging the mould cavity.
 The amount of taper depends upon:
i. Shape and size of pattern in the depth direction in
contact with the mould cavity.
ii. Moulding methods.
iii. Mould materials.
iv. Draft allowance is imparted on internal as well as
external surfaces; of course it is more on internal
surfaces.
107 108

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Fig: Taper in design
109
Table 2 : Draft Allowances of Various Materials:
Pattern material
Height of the
given surface
(inch)
Draft angle
(External surface)
Draft angle
(Internal surface)
Wood
1
1 to 2
2 to 4
4 to 8
8 to 32
3.00
1.50
1.00
0.75
0.50
3.00
2.50
1.50
1.00
1.00
Metal and plastic
1
1 to 2
2 to 4
4 to 8
8 to 32
1.50
1.00
0.75
0.50
0.50
3.00
2.00
1.00
1.00
0.75
110
4. Distortion or Camber allowance:
A casting will distort or wrap if:
i. It is of irregular shape,
ii. All it parts do not shrink uniformly i.e., some parts shrinks
while others are restricted from during so,
iii. It is u or v-shape,
iv. The arms possess unequal thickness,
v. It has long, rangy arms as those of propeller strut for the
ship,
vi. It is a long flat casting,
vii. One portion of the casting cools at a faster rate as
compared to the other.
111 112
5. Shake Allowance:
 A pattern is shaken or rapped by striking the same with a
wooden piece from side to side. This is done so that the
pattern a little is loosened in the mold cavity and can be
easily removed.
 In turn, therefore, rapping enlarges the mould cavity which
results in a bigger sized casting.
 Hence, a –ve allowance is provided on the pattern i.e., the
pattern dimensions are kept smaller in order to compensate
the enlargement of mould cavity due to rapping.
 The magnitude of shake allowance can be reduced by
increasing the taper.
113
Die Casting
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Die Casting
115 116
Casting Defects
Blowholes:
 Blowholes/Pinholes: These defects can appear in any region of a
casting. They are caused when gas is trapped in the metal during
solidification.
 Caused due to excess moisture content in moulding sand or low
permeability/venting.
Scab
 It is caused when sand erodes from mould due to uneven
ramming and the recess is filled with metal.
Scar and blister
 Due to improper permeability or venting. A scar is a shallow
blow. It generally occurs on flat surf; whereas a blow occurs on
a convex casting surface. A blister is a shallow blow like a scar
with thin layer of metal covering it.
117
Casting Defects
Wash
 They appear as rough spots or areas of excess metal, and are caused
by erosion of moulding sand by the flowing metal.
 This is due to loose ramming of moulding sand, and not having enough
strength and if the molten metal flowing at high velocity.
 The former can be taken care of by proper choice of moulding sand
and the latter can be overcome by the proper design of the gating
system.
Misrun
 A mis-run is caused when the metal is unable to fill the mould cavity
completely and thus leaves unfilled cavities.
 A mis-run results when the metal is too cold to flow to the extremities
of the mould cavity before freezing.
 Long, thin sections are subject to this defect and should be avoided in
casting design.
118
Casting Defects
Cold shut
• A cold shut is caused when two streams while meeting in the mould
cavity, do not fuse together properly thus forming a discontinuity in
the casting.
• When the molten metal is poured into the mould cavity through more-
than-one gate, multiple liquid fronts will have to flow together and
become one solid.
• If the flowing metal fronts are too cool, they may not flow together, but
will leave a seam in the part and is called a cold shut, and can be
prevented by superheat in the poured metal and sufficiently thick walls
in the casting design.
• The mis-run and cold shut defects are caused either by a lower fluidity
of the mould or when the section thickness of the casting is very small.
Fluidity can be improved by changing the composition of the metal
and by increasing the pouring temperature of the metal. 119
Casting Defects
Hot Tear
Hot tears are cracks which appear when the solidifying melt does not
have sufficient strength to resist tensile forces produced during
solidification.
They may be due to
 excessively high temperature of casting metal,
 increased metal contraction,
 incorrect design of the gating system or casting,
 poor deformability of the cores, and
 non-uniform cooling which gives rise to internal stresses.
This defect can be avoided by improving the design of the casting and
by having a mould of low hot strength and large hot deformation.
120

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Extrusion is defined as the process of shaping material, by
forcing it to flow through a shaped opening in a die.
Extruded material emerges as an elongated piece with the
same profile as the die opening.
Drawing is defined as the process of shaping material, by
pulling the material through a shaped opening in a die
(draw die).
This process of drawing is not to be confused with the
drawing process related to the forming of sheet metals
Extrusion and Drawing
121
Extruded items
 Railings for sliding doors
 Window frames
 Tubing having various
cross-sections
 Aluminum ladders
 Numerous structural and
architectural shapes
 Rods and wires Including:
 Rods for shafts
 Machine and structural
components
 Electrical wiring
 Tension-loaded structural
members
 Welding Electrodes
 Springs, Cables & Paper clips
 Spokes for bicycle wheels
 Stringed musical instruments
Drawing Products
122
Extrusion
• Metal is compressed and forced to flow through a shaped
die to form a product with a constant cross section
• A ram advances from one end of the die and causes the
metal to flow plastically through the die
Figure Direct extrusion schematic showing the various equipment components.
(Courtesy of Danieli Wean United, Cranberry Township, PA.)
123
Extrusion
• Definition:
– Process of forcing a billet through a die above its
elastic limit, taking shape of the opening.
• Purpose:
– To reduce its cross-section or to produce a solid or
hollow cross section.
• Analogy: “Like squeezing toothpaste out of a tube”.
124
Extrusion
 Extruded products always have a constant cross-section.
 It can be a semi-continuous or a batch process.
 Extrusions can be cut into lengths to become discrete
parts like gears, brackets, etc.
 A billet can also extruded individually in a chamber, and
produces discrete parts.
 Typical products: railings, tubing, structural shapes, etc.
125
Typical Extruded Products
(Left) Aluminum products. (Right) Steel products.
Figure Typical shapes produced by extrusion.
(Courtesy of Aluminum Company of America, Pittsburgh, PA.). (Courtesy of Allegheny
Ludlum Steel Corporation, Pittsburgh, PA.)
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Extrusion
• Can be performed at elevated temperatures or room
temperatures, depending on material ductility.
• Commonly extruded materials include aluminum,
magnesium (low yield strength materials), copper, and
lead.
• Steels and nickel based alloys are far more difficult to
extrude (high yield strength materials).
• Lubricants are essential to extrude high strength alloys
to avoid tendency of material to weld to die walls.
127
Advantages of Extrusion
• Many shapes can be produced that are not possible
with rolling
• No draft is required
• Amount of reduction in a single step is only limited
by the equipment, not the material or the design
• Dies are relatively inexpensive
• Small quantities of a desired shape can be produced
economically
128
Extrusion Methods
Methods of extrusion:
Hot extrusion is usually done by either the direct or indirect methods.
– Direct extrusion
 Solid ram drives the entire billet to and through a stationary die.
 Must provide additional power to overcome friction between billet
surface and die walls.
– Indirect extrusion
 A hollow ram pushes the die back through a stationary, billet.
 No relative motion and no friction between billet and die walls.
 Lower forces required, can extrude longer billets.
 More complex process, more expensive equipment required.
129
Extrusion Methods
Fig. Direct and Indirect extrusion.
In direct extrusion, the ram and billet both move and friction
between the billet and the chamber opposes forward motion.
For indirect extrusion, the billet is stationary. There is no billet-
chamber friction, since there is no relative motion. 130
Extrusion of Hollow Shapes
• Mandrels may be used to produce hollow shapes or shapes
with multiple longitudinal cavities.
Fig. Two methods of extruding hollow shapes using internal mandrels.
(a) the mandrel & ram have independent motions; (b) they move as a single unit.
131
Cold Extrusion
Fig. (Right)
Steps in the
forming of a
bolt by cold
extrusion, cold
heading and
thread rolling.
Fig.
(a) Reverse
(b) forward
(c) combined
forms of cold
extrusion.
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Drawing
• Cross section of a round rod / wire is reduced by
pulling it through a die.
• Work has to be done to overcome friction. Force increases
with increasing friction.
• Cannot increase force too much, or material will reach
yield stress.
• Maximum reduction in cross-sectional area per pass =
63%.
• To produce a desired size or shape, multiple draws may be
required through a series of progressively smaller dies.
• Intermediate annealing may also be required to restore
ductility and enable further deformation.
133
Deep Drawing
Blanking
Deep Drawing
Redrawing
Ironing
Doming
Necking
Seaming
134
135
Examples of
Deep
Drawing
136
Tube and Wire Drawing
• Tube sinking does not use a
mandrel
– Internal diameter precision is
sacrificed for cost and a floating
plug is used
Fig. Tube drawing with a floating
plug.
Fig. Schematic of wire drawing with a
rotating draw block. The rotating motor on
the draw block provides a continuous pull
on the incoming wire. 137
Examples of Sheet metal parts
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Bending
• Beyond yield strength but below the ultimate
tensile strength
• Placed on die and bent using a simple punch.
139
Bending Mechanism
140
What is Spinning?
• Spinning is the process of forming sheet metals or
tubing into contoured and hollow circular shapes.
141
Conventional Spinning- Mandrel
142
Forging
Forging is defined as the controlled plastic
deformation of metal at elevated temperatures into a
predetermined size or shape by operations like
hammering, bending and pressing etc.
These operations can be carried out by hand
hammers, power hammers, drop hammers or by forging
machines.
Forging is generally employed for those components
which require high strength and resistance to shock or
vibration and uniform properties.
Forging Tools
• Smith’s forge or hearth
• Swage block
• Tongs
• Punches and drafts
• Swages
• Flatter
• Anvil
• Sledge hammers
• Chisels
• Fullers
• Set hammer
• Beck iron
144

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Forging Operations
• Upsetting
• Drawing
• Setting down
• Cutting
• Bending
• Welding
• Punching
• Rotary swaging
• Cold heading
• Riveting and stacking
• Hobbing
• Coining
• Embossing
145
Forging Operations
Upset forging
Upsetting
FINISHED PART
Bending (on Anvil)Setting down Punching 146
Forging Operations
Cold heading
Riveting
CoiningHobbing Embossing
Stamping
147
Rolling
•Rolling is a process of compressing and squeezing a
metal piece between two rolls rotating in opposite
directions.
•It is the method of forming metal into desired shapes by
plastic deformation as the metal passes between the
rolls.
•Rolling is used to produce structural shapes like
channels, I-beams, rail-road rails, bars of circular or
hexagonal cross-section and sheets, plates etc.
Types of Rolls
• Grooved Roll
produce structural shapes, like channels, angles etc.
• Plain Roll
produce sheets, plates, strips etc.
149
Methods of Rolling
• Hot Rolling
• Cold Rolling
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Rolling Mills
• Two-high reversing mill
• Three-high mill
151
Rolling
152
Welding
Welding is the process of joining two pieces
of metal by application of heat.
 Soldering and brazing are adhesive bonds,
whereas welding is a cohesive bond.
Arc Welding
Arc welding is used in fusion processes for joining metals
and alloys.
The heat required is developed by striking an arc between a
metal rod and the parts to be joined.
By applying intense heat, metal at the joint between two
parts is melted and caused to intermix - directly, or more
commonly, with an intermediate molten filler metal. Upon
cooling and solidification, a metallurgical bond is created.
Since the joining is an intermixture of metals, the final
weldment potentially has the same strength properties as the
metal of the parts.
Energy for the arc is provided by AC transformed from the
mains supply to 50-100V, 10-300A. DC may be used at 40-60V.
Arc Welding Prepared joints for Arc Welding

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Welding Operation
Before welding, earthing connections should be
checked, voltage and amperage has to be
adjusted.
welding rod is selected to suit the nature and
thickness of the metal to be joined.
157 158
Gas Welding
In gas welding, combustion is obtained by
mixing oxygen with a fuel to support combustion
at high temperature.
The most common fuel is acetylene. The fuel gas
could also be hydrogen, natural or producers gas.
Oxy-Acetylene Welding
CaC2 + 2H2O = C2H2 + Ca(OH)2
Calcium Carbide Water Acetylene Hydrated lime
Types of Flames
• Carburizing flame - excess of acetylene
• Neutral flame - aprox. equal volume of O2 and C2H2
• Oxidizing flame
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Machining
(a) Purpose of Machining
• Most of the engineering components such as gears, bearings,
clutches, tools, screws and nuts etc. need dimensional and form
accuracy and good surface finish for serving their purposes.
• Preforming like casting, forging etc. generally cannot provide
the desired accuracy and finish.
• Such preformed parts are called blanks, and need semi-finishing
or finishing and is done by machining and grinding. Grinding is
also basically a machining process.
• Machining to high accuracy and finish enables a product to:
• fulfill its functional requirements
• improve its performance
• prolong its service
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(b) Principle of Machining
• The basic principle of machining is illustrated in Figure.
• A metal rod of irregular shape, size and surface is
converted into a finished rod of desired dimension and
surface by machining by proper relative motions of the
tool-work pair.
163
Definition of Machining:
• Machining is an essential process of finishing by
which jobs are produced to the desired dimensions
and surface finish by gradually removing the excess
material from the preformed blank in the form of
chips with the help of cutting tool(s) moved past the
work surface(s).
164
Machining Requirements
The essential requirements for machining work are schematically illustrated as
The blank and the cutting tool are properly mounted (in fixtures) and moved
in a powerful device called machine tool enabling gradual removal of
material from the work surface resulting in its desired dimensions and
surface finish.
Additionally environment like cutting fluid is generally used to ease
machining by cooling and lubrication. 165
Basic functions of Machine Tools
• Machine Tools basically produce geometrical surfaces like
flat, cylindrical or any contour on the preformed blanks by
machining work with the help of cutting tools.
• The physical functions of a Machine Tool in machining
are:
 firmly holding the blank and the tool.
 transmit motions to the tool and the blank.
 provide power to the tool-work pair for the machining
action.
 control of the machining parameters, i.e., speed, feed and
depth of cut.
166
Machine Tool - definition
• A machine tool is a non-portable power operated and
reasonably valued device or system of devices in
which energy is expended to produce jobs of desired
size, shape and surface finish by removing excess
material from the preformed blanks in the form of
chips with the help of cutting tools moved past the
work surface(s).
167
Lathe
The main function of a lathe is to remove the metal from
the piece of work to give it the required shape & size.
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 This is accomplished by holding the work securely &
rigidly on the machine & then turning it against a
cutting tool, which will remove metal from the work in
the form of chips.
 If the tool is moved parallel to the axis of rotation of
the work then a cylindrical surface is produced as
shown.
 If the tool is moved perpendicular to the axis of
rotation of the work, then a flat surface is produced as
shown.
169
Working Principle of a lathe
170
Diagram of a Lathe
171
Schematic Diagram of a Lathe
172
Diagram of a Lathe
173
Specification of a lathe
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Principal parts of a Lathe
 Bed: - the body structure supported at both ends. The head
stock, tail stock, carriage etc. are mounted on it. The bed
provides required strength and rigidity to the machine.
 Head stock:-the head stock is mounted on the bed at the left end
permanently. It has got a gear box for getting different speeds
for the spindle and work piece.
 Tail stock: - this is mounted on the right hand end of the bed
which can however clamp at any position. Tail stock supports
one end of work piece and used for holding the tool for drilling
and reaming operations.
175
Lathe Bed
176
 Carriage: -the carriage consists of so many parts that serve to
support the cutting tool and control the action of the cutting tool. It
can be moved along the bed ways provided at the top of the bed.
 Lathe centers: -these are tapered components fit in to spindles
provided in the tail stock and head stock. The center fitted to the tail
stock is called dead center which supports the work piece and that
connected to the head stock is called live center since it will rotate
along with the spindle.
 Tool post: -tool post is mounted on the carriage to hold the cutting
tool and enable the cutting tool to be adjusted to a convenient
position.
 Lead screw: -this is a long threaded shaft used for cutting threads
and to give automatic movements to carriage and cross slide to
achieve the tool movements in the longitudinal and lateral
directions with respect to the bed.
Principal parts of a Lathe
177
Compound Rest & Tool Post
178
Chucks
179
Holding & Turning job
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Various operations performed on lathe
Facing
 facing is the operation of producing flat end surface that is
normal to the axis of rotation.
 While facing cutting tool is moved right angles to the axis of
rotation and the cutting edge must be set at the same height at
the centre of the work.
181
TURNING
182
Drilling:
 Drilling is a process used extensively by which through or
blind holes are originated or enlarged in a work piece.
 This process involves feeding of a cutting tool (drill) into a
rotating work piece fixed on a chuck.
183
Boring
 It is the operation of enlarging the previously drilled hole
with the aid of single point cutting tool called boring tool.
 The feed is given parallel to the axis of revolution.
184
REAMING
The process of making a hole smoothly and
accurately, holes may be reamed by a straight
shank or taper shank reamer.
185
Thread Cutting (Internal & External)
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Knurling
The process of indentation of various forms on
cylindrical work surfaces, a knurl tool is held in tool
post and pressed against the rotating work piece with a
cross slide and then it is fed for required length with the
carriage.
187
Chamfering
 It is the beveling or turning at the end of the work
piece.
 This operation is done to remove burrs from the end of
work piece.
188
Drilling Machine
189 190
Shaper
It is reciprocating type of machine tool used for producing flat
surfaces. Surfaces may be horizontal, vertical or inclined.
191
Working Principle of a Shaper
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Machining
vertical surfaces:
Machining
horizontal surfaces:
193
Milling Operations
 Milling is the removal of metal by feeding the work
past a rotating multi toothed cutter.
 In this operation the material removal rate (MRR) is
enhanced as the cutter rotates at a high cutting speed.
 The surface quality is also improved due to the multi
cutting edges of the milling cutter.
194
195
Milling Cutters
 The action of the milling cutter is totally different from that
of a drill or a turning tool.
 In turning and drilling, the tools are kept continuously in
contact with the material to be cut.
 whereas milling is an intermittent process, as each tooth
produces a chip of variable thickness.
196
UP MILLING DOWN MILLING
197
1.Face milling
2. Side milling
3.End milling
4.T-slot milling
5.Angular milling
6.Form milling
7.Gear cutting
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Grinding Machine
 The process of metal removal by a rotating abrasive
wheel is called grinding.
 The wheels are made of abrasive materials called
silica, bauxite, mixed with the bonding material and
casting in the form of wheels of different diameters
and shapes.
 The feed is given to the work while the wheel rotates.
199 200
Surface Grinding Machine
work
201 202
Computer Integrated Manufacturing
• Computer-integrated manufacturing (CIM), integrates the
software and hardware needed for computer graphics,
computer-aided modelling and computer-aided design and
manufacturing activities, from initial product concept through its
production and distribution in the marketplace.
• This comprehensive and integrated approach began in the 1970s
and has been particularly effective because of its capability of
making possible the following tasks:
 Responsiveness to rapid changes in product design modifications
and to varying market demands.
 Better use of materials, machinery, and personnel.
 Reduction in inventory.
 Better control of production and management of the total
manufacturing operation.
203
Computer Integrated Manufacturing
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Elements in CIM
1. Computer numerical control (CNC).
First implemented in the early 1950s, this is a method of
controlling the movements of machine components by the direct
insertion of coded instructions in the form of numerical data.
2. Adaptive control (AC).
The processing parameters in an operation are automatically
adjusted to optimize the production rate and product quality and to
minimize manufacturing cost. For example, machining forces,
temperature, surface finish, and the dimensions of the part can be
constantly monitored; if they move outside the specified range, the
system adjusts the appropriate variables until the parameters are
within the specified range.
205
Elements in CIM
3. Industrial robots.
Introduced in the early 1960s, industrial robots have rapidly been
replacing humans, especially in operations that are repetitive,
dangerous, and boring. As a result, variability in product quality is
decreased and productivity improved. Robots are particularly
effective in assembly operations, and some (intelligent robots) have
been developed with sensory perception capabilities and movements
that simulate those of humans.
4. Automated materials handling.
Computers have made possible highly efficient handling of
materials and components in various stages of completion (work in
progress), as in moving a part from one machine to another, and
then to points of inspection, to inventory, and finally, to shipment.
206
Elements in CIM
5. Automated assembly systems.
These systems continue to be developed to replace assembly by
human operators, although humans still have to perform some
operations. Assembly costs can be high, depending on the type of
product; consequently, products are now being designed so that
they can be assembled more easily, and faster by automated
machinery, thus reducing the total manufacturing cost.
6. Computer-aided process planning (CAPP).
By optimizing process planning, this system is capable of
improving productivity, product quality, and consistency and hence
reducing costs. Functions such as cost estimating and monitoring
world standards (time required to perform a certain operation) are
also incorporated into the system.
207
Elements in CIM
7. Just-in-time production (JIT).
The principle behind JIT is that
(1)supplies of raw materials and parts are delivered to the
manufacturer just in time to be used,
(2)parts and components are produced just in time to be made
into subassemblies, and
(3)products are assembled and finished just in time to be
delivered to the customer.
As a result, inventory carrying costs are low, defects in components
are detected right away, productivity is increased, and high-quality
products are made at low cost.
208
Elements in CIM
8. Group technology (GT).
The concept behind group technology is that parts can be grouped
and produced by classifying them into families according to
similarities in design and the manufacturing processes employed
to produce them. In this way, part designs and process plans can
be standardized and new parts (based on similar parts made
previously) can be produced efficiently and economically.
9. Cellular manufacturing (CM).
This system utilizes workstations that consist of a number of
manufacturing cells, each containing various production machines
controlled by a central robot, with each machine performing a
different operation on the part, including inspection.
209
Elements in CIM
10. Flexible manufacturing systems (FMS).
These systems integrate manufacturing cells into a large production
facility, with all of the cells interfaced with a central computer.
Although very costly, flexible manufacturing systems are capable of
producing parts efficiently, but in relatively small quantities, and of
quickly changing manufacturing sequences required for different
parts. Flexibility enables these systems to meet rapid changes in
market demand for all types of products.
11. Expert systems (ES).
Consisting basically of complex computer programs, these systems
have the capability of performing various tasks and solving difficult
real-life problems, much as human experts would, including
expediting the traditional iterative process in design optimization.
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Elements in CIM
12. Artificial intelligence (AI).
Computer-controlled systems are now capable of learning from
experience and of making decisions that optimize operations
and minimize costs, ultimately replacing human intelligence.
13. Artificial neural networks (ANN).
These networks are designed to simulate the thought processes
of the human brain, with such capabilities as modelling and
simulating production facilities, monitoring and controlling
manufacturing processes, diagnosing problems in machine
performance, and conducting financial planning and managing
a company’s manufacturing strategy.
211
Lean Production
Lean production is a methodology that involves a
thorough assessment of each activity of a company, with
the basic purpose of minimizing waste at all levels and
calling for the elimination of unnecessary operations that
do not provide any added value to the product being
made.
This approach, also called lean manufacturing, identifies
all of a manufacturer’s activities from the viewpoint of the
customer and optimizes the processes used in order to
maximize added value.
212
Lean Production
• Lean production focuses on
(a) The efficiency and effectiveness of each and every
manufacturing operation,
(b) The efficiency of the machinery and equipment used, and
(c) The activities of the personnel involved in each operation.
This methodology also includes a comprehensive
analysis of the costs incurred in each activity and
those for productive and for non productive
labour.
213
Lean Production
• The lean production strategy requires a fundamental
change in corporate culture, as well as an
understanding of the importance of cooperation and
teamwork among the company’s workforce and
management.
• Lean production does not necessarily require cutting
back on a company’s physical or human resources;
rather, it aims at continually improving efficiency and
profitability by removing all waste in the company’s
operations and dealing with any problems as soon as
they arise.
214
Agile Manufacturing
• The principle behind agile manufacturing is ensuring agility
and hence flexibility-in the manufacturing enterprise, so that
it can respond rapidly and effectively to changes in product
demand and the needs of the customer.
• Flexibility can be achieved through people, equipment,
computer hardware and software, and advanced
communications systems.
• As an example of this approach, it has been predicted that
the automotive industry could configure and build a car in 3
days and that, eventually, the traditional assembly line will
be replaced by a system in which a nearly custom made car
will be produced by combining several individual modules.
215
Agile Manufacturing
• The methodologies of both lean and agile production
require that a manufacturer benchmark its operations.
• Benchmarking involves assessing the competitive
position of other manufacturers with respect to one’s
own position (including product quality, production
time, and manufacturing cost) and setting realistic
goals for the future.
• Benchmarking thus becomes a reference point from
which various measurements can be made and to
which they can be compared.
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Environmentally Conscious
Manufacturing
• An inherent feature of virtually all manufacturing processes is
waste. The most obvious examples are material removal
processes, in which chips are removed from a starting work piece
to create the desired part geometry. Waste in one form or another
is a by-product of nearly all production operations.
• Another unavoidable aspect of manufacturing is that power is
required to accomplish any given process. Generating that power
requires fossil fuels, the burning of which results in pollution of
the environment.
• At the end of the manufacturing sequence, a product is created
that is sold to a customer. Ultimately, the product wears out and
is disposed of, perhaps in some landfill, with the associated
environmental degradation.
217
Environmentally Conscious
Manufacturing
• More and more attention is being paid by society to the
environmental impact of human activities throughout the
world and how modern civilization is using our natural
resources at an unsustainable rate.
• Global warming is presently a major concern. The
manufacturing industries contribute to these problems.
• Environmentally conscious manufacturing refers to
programs that seek to determine the most efficient use of
materials and natural resources in production, and
minimize the negative consequences on the environment.
218
Environmentally Conscious
Manufacturing
• Other associated terms for these programs include green
manufacturing, cleaner production, and sustainable
manufacturing.
• They all boil down to two basic approaches:
(1) design products that minimize their environmental impact,
(2) design processes that are environmentally friendly.
• Product design is the logical starting point in environmentally
conscious manufacturing.
219
Design For Environment (DFE)
• The term design for environment (DFE) is sometimes used for the
techniques that attempt to consider environmental impact during
product design prior to production.
• Considerations in DFE include the following:
(1) select materials that require minimum energy to produce,
(2) select processes that minimize waste of materials and energy,
(3) design parts that can be recycled or reused,
(4) design products that can be readily disassembled to recover the parts,
(5) design products that minimize the use of hazardous and toxic materials,
(6) give attention on how the product will be disposed at the end of its useful
life.
• To a great degree, decisions made during design dictate the materials
and processes that are used to make the product. These decisions limit
the options available to the manufacturing departments to achieve
sustainability.
220
Design For Environment (DFE)
• However, various approaches can be applied to make plant
operations more environmentally friendly. They include the
following:
(1) adopt good housekeeping practices—keep the factory clean,
(2) prevent pollutants from escaping into the environment (rivers and
atmosphere),
(3) minimize waste of materials in unit operations,
(4) recycle rather than discard waste materials,
(5) use net shape processes,
(6) use renewable energy sources when feasible,
(7) provide maintenance to production equipment so that it operates at
maximum efficiency,
(8) invest in equipment that minimizes power requirements. 221
Organization for Manufacture
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Organization for Manufacture
223
Organization for Manufacture
224
Organization for Manufacture
225
Organization for Manufacture
226
THE END
227