2. CASTING
• It is a manufacturing process in which molten metal is
poured in a mould or cavity and allowed tosolidify
• Molten metal on solidification gets the shape of themould
• Mould has the shape of the product to bemade
4. SAND CASTING
• Molten metal: metal in the form of a liquid
• Mould: negative print of the product to be cast (cavity
whose geometry determines the shape of the cast part),
open and closed mould
• Moulding: process of making mould of desired shape using
sand, pattern and core
Mould consists of two halves
a) Cope: upper half of the mould
b) Drag: bottom half of the mould
8. • Pouring basin: top of the mould for pouring the molten
metal at the required rate into the mouldcavity
• Sprue: vertical passage made through the cope for
connecting pouring basin with the gate
• Runner: for connecting the sprue and gate
• Gates: passage for connecting the base of the runner with
the mould cavity
• Riser: passage made in the cope to permit molten metal to
rise up after filling the mould cavity
9.
10. • Pattern: model or replica of the component to be made
by casting( mould formingtool)
Types of patterns are
• One piece pattern
• Split pattern
• Loose piece pattern
• Match plate pattern
• Cope and Drag pattern
18. • Core: solid mass prepared using dry sand, in order to
introduce into the mould cavity, to form a hole
• Core produces a hollow casting
Types of core
• Horizontal core
• Vertical core
• Hanging core
31. MOULDING SAND PROPERTIES
• FLOWABILITY: behave like a fluid, sand to get compacted to
uniform density
• GREEN STRENGTH: strength of the sand in moistcondition
• DRY STRENGTH: strength of the sand in dry condition
• POROSITY/ PERMEABILITY: ability to allow the passage of
mould gases
• REFRACTORINESS: ability of the sand to withstand high
temperature
32. • ADHESIVENESS: ability of the sand to stick on to the mould
walls
• CHEMICAL STABILITY: resist chemical reaction
• COLLAPSIBILITY: ability of the sand to collapse after the
casting solidifies
• FINENESS: ability of the sand to produce smooth surfaced
castings
• COEFFICIENT OF EXPANSION: less coefficient of expansion
• DURABILITY: ability of the sand to be used again and again
33. Advantages
• Production process is simple
• Cost of casting is low
• Sand can be reused
Disadvantages
• More chances of defects
• Does not impart good surfacefinish
34. METAL MOULD CASTING
• Process in which molten metal is poured/forced into metal
mould cavities
• It requires less floor space
35. 1. Permanent Mould Casting
• The moulds(dies) are made in two halves, hinged together to
facilitate quick opening and closing and removal ofcasting
• Filling the mould is achieved due togravity
• One half is movable called movable die
• Other half is stationary called stationary die
• Ejector pins are used for ejecting out the casting from the
die
• Clamps are used for clamping the two halves of the die
together
36.
37.
38.
39.
40. 2. DIE CASTING
• Molten metal is forced into mould cavity under pressure
• Pressure is obtained by compressed air orhydraulically
• Two types
a) Hot chamber process
b) Cold chamber process
• Ejector pins are used for ejecting out the casting from the die
• Clamps are used for clamping the two halves of the die
together
41. a. Hot Chamber Die Casting
• Plunger is activated by compressed air or by hydraulic
pressure
• Intake Port allows the molten metal to enter thecylinder
• Plunger moves downward, closes the intake port and
applies pressure on the moltenmetal
• Molten metal is forced into the die cavity
• After solidification, plunger moves upward, uncovers intake
port and hot molten metal enters thecylinder
42.
43.
44. b. Cold Chamber Die Casting
• Metal is melted separately and transferred to the cylinder
using a hand ladle
• Molten metal is forced into the die cavity by applying
pressure on the plunger
• After solidification, die is opened and the casting is ejected
45.
46.
47. CASTING DEFECTS
• Blowholes: holes below the surface of casting, not visible
from outside
• Inclusions: foreign material in the casting
• Swell: localized enlargement of the casting
• Scab: erosion or breaking down a portion of the mould
• Honey combing: small cavities present on the castingsurface
• Misrun: molten metal fails to reach all the sections of the
mould
• Fin: thin projection of metal, which is not a part of thecasting
• Shift: mismatching of casting sections
56. Forging is a process in which material is shaped
by the application of localized compressive forces exerted
manually or with power hammers, presses or special forging
machines.
The process may be carried out on materials in either hot or cold
state.
The term forging usually implies hot forging carried out at
temperatures which are above the recrystallization temperature of
the material.
Forging is an effective method of producing many useful
shapes.
2
57. Typical forged parts include rivets, bolts, crane hooks, connecting
rods, gears, turbine shafts, hand tools, railroads, and a variety of
structural components used to manufacture machinery.
The forged parts have good strength and toughness;
hence they can be used reliably for highly stressed and
critical applications.
Forgeability is the ease with which a given metal can be
forged into the required shape.
57
58. For forging the metal must be heated to a temperature at which it
will possess high plastic properties both at the beginning and
end of the process.
Excess temperature may result in the formation of oxides also the
insufficient temperature will not introduce sufficient plasticity
in the metal to shape.
So Temperature at which forging is finished has an
important influence on the properties of forging.
58
59. Advantages of Forging
Since forging gives a finished product, excess metal removal
is not required as in machined products.
and toughness are
Forging improves directional properties.
Mechanical properties like strength
improved.
Metals can be easily shaped to the required dimensions in
forging dies.
Heavy products can be formed easily compared to other
process.
59
60. Limitations of Forging
The initial and maintenance cost of equipments and dies is
high.
Intricate shapes cannot be produced by forging.
The shape and size is limited as compared to casting process.
The forged part costs more than the cast part.
60
61. Different types of forging operations
Upsetting
Drawing down
Fullering
Edging
Swaging
Forge welding
Deep drawing
Punching
Blanking
61
62. Upsetting
Upset forging involves increasing the cross section
of a material at the expense of its corresponding
length.
Upset forging was initially developed for making
bolt heads in a continuous manner, but presently it
is the most widely used of all forging processes.
62
63. Fig (a) Solid cylindrical billet upset between two flat dies.
(b) Uniform deformation of the billet without friction. (c)
Deformation with friction. Note barreling of the billet
caused by friction forces at the billet-die interfaces.
63
64. Drawing Down
Drawing is used to reduce the cross-sectional area of the work
piece with concurrent increase in length
Fig Drawing operation
64
65. Fullering
Fullering is used to reduce the cross-sectional area of a portion
of the stock. The metal flow is outward and away from the
centre of the fuller.
Fullering
65
66. Edging
Edging is the process of concentrating material using an
concave shaped open die. The process is called edging,
because it is usually carried out on the ends of the workpiece.
Fig Edging
67. Swaging
Swaging is used to produce a bar with a smaller diameter (using concave
dies).
Two swage blocks top swage and bottom swage are used for the swaging operation.
The job is held between the top and bottom swages and is hammered.
Screwdriver blades and soldering iron tips are typical
examples of swaged products.
68. Forge Welding
Forge welding is a solid state process that joins two pieces
of metal by heating them to a high temperature and then
hammering them together.
The process is one of the simplest methods of joining
metals and has been used since ancient times.
69. Deep drawing
Deep drawing is the process of forming a flat metal piece
into a hollow shape (or cup shape) by means of a punch
which causes the blank (metal piece) to flow in to the die
cavity.
During this operation the flat metal piece is placed over a
circular die opening. The punch moves down and forces
the blank in to the die cavity.
69
70. Punching/Blanking
Punching or blanking is a process in which the punch removes a
portion of material from the larger piece or a strip of sheet metal.
If the small removed piece is discarded, the operation is
called punching, whereas if the small removed piece is the
useful part and the rest is scrap, the operation is called
blanking.
70
73. Some common forging processes
are:
Open die hammer forging
Hand forging
Impression die drop forging
Press Forging
Roll forging
74. Open Die Hammer Forging.
It is the simplest forging process which is quite flexible but
not suitable for large scale production.
It is a slow process.
The resulting size and shape of the forging are dependent
on the skill of the operator.
This process is most often used to make near final shape of
the part so that some further operation done on the job
produces the final shape.
76. Impression Die Drop Forging (Closed Die Forging)
The process uses shaped dies to control the flow of
metal. The heated metal is positioned in the lower cavity
and on it one or more blows are struck by the upper die.
This hammering makes the metal to flow and fill the die
cavity completely.
Excess metal is squeezed out around the periphery of the
cavity to form flash.
On completion of forging, the flash is trimmed off with
the help of a trimming die.
77.
78. Auto Forging:
This is a modified form of impression die forging, used mainly
for non ferrous metals.
In this a cast perform, as removed from the mold while hot, is
finish forged in a die.
The flash formed during die forging is trimmed later in the
usual manner.
As the four steps of the process casting, transfer from mold to
the forging die, forging, and trimming are in most applications
completely mechanized, the process has acquired the name
Auto forging.
79. Net - shape forging (Precision Forging)
The metal is deformed in cavity so that no flash is formed and
the final dimensions are very close to the desired component
dimensions.
There is minimum wastage of material and need for subsequent
machining operation is almost eliminated.
The process uses special dies having greater accuracies than
those in impression die forging, and the equipment used is also
of higher capacity.
Typical precision forged components are gears, turbine blades,
fuel injection nozzles, and bearing casings.
Because of very high cost of toolings and machines, precision
forging is preferred over conventional forging only where
volume of production is extremely large.
82. Sl no Open Die Forging Closed Die Forging
1 Work piece is struck between
two flat surfaces
Cavities or impressions are cut in the
dies and the metal is forced to occupy
the cavity in the die
2 Used when number of
components to be forged is less.
Used when number of components to
be forged is more
3 Used for large sized parts Used for small and medium sized
parts
4 More time is needed Requires less time
5 Less dimensional accuracy Good dimensional accuracy
6 Complicated shapes cannot be
obtained
Complicated shapes can be obtained
7 Skilled labour is needed Skilled labour is not needed
8 Initial cost is less Initial cost is more
Comparison between Open Die forging and Closed Die forging
83. Press Forging
Press forging, which is mostly used for forging of large sections
of metal, uses hydraulic press to obtain slow and squeezing
action instead of a series of blows as in drop forging.
The continuous action of the hydraulic press helps to obtain
uniform deformation throughout the entire depth of the
work piece.
Therefore, the impressions obtained in press forging are
more clean.
Dies are generally heated during press forging to reduce
heat loss, promote more uniform metal flow and production
of finer details.
85. Roll Forging
This process is used to reduce the thickness of round or flat bar
with the corresponding increase in length.
Examples of products produced by this process include leaf
springs, axles, and levers.
The process is carried out on a rolling mill that has two semi
cylindrical rolls that are slightly eccentric to the axis of
rotation.
Each roll has a series of shaped grooves on it. When the rolls
are in open position, the heated bar stock is placed between the
rolls.
With the rotation of rolls through half a revolution, the bar is
progressively squeezed and shaped.
The bar is then inserted between the next set of smaller grooves
and the process is repeated till the desired shape and size are
achieved.
86. Forging Defects
The common forging defects are the following.
Cracks: Cracks occur due to uneven heating, forging at low
temperature or incorrect cooling of the forged part.
Laps: Laps form when metal folds over itself while forging.
Dirt, Slag and Sand: Dirt, Slag and Sand may be found in
the ingot used for forging.
Blow holes: Blow holes may remain in the forgings if they
are present in the ingots.
Cold Shuts: Cold shuts are small cracks at the surface
caused by poor die design.
Mismatch: Due to the improper alignment of the lower and
upper die.
88. • Process of plastically deforming metal by passing it
between rolls
• Cylindrical rolls are used to reduce the cross sectional
area of a bar or plate with a corresponding increase in the
length
• Process of rolling basically consists of passing metal
between two rolls rotating in opposite direction at the
same speed
Two types
• Hot rolling
• Cold rolling
89.
90. 1. Hot Rolling
Process in which metal is fed to the rolls after being heated
above the recrystallizationtemperature
91.
92. 2. Cold Rolling
In cold rolling, metal is fed to the rolls when it is below the
recrystallization temperature
93.
94. Types of rolling mills
a) Two high mill
b) Three high mill
c) Four highmill
d) Cluster mill
e) Tandem mill
96. • Two rolls
• Lower roll will be fixed
• Upper roll can be moved to adjust the space between the
rolls
• Both the rolls rotate at the same speed but in opposite
directions
99. • Three rolls positioned one over another
• Upper and lower rolls rotate in the same direction
• Middle roll rotates in the oppositedirection
• Middle roll is fixed
• Upper and lower rolls are moved to adjust the rollgap
104. • Used for rolling very thin sheet or foils
• It consists of a Pair of working rolls of very small diameter,
supported by a number of back up rolls on eitherside
107. • Series of rolling mills are placed one after another
• Different reduction takes place at each stand, the strip
will be moving at different velocities
108. EXTRUSION
->A round billet is placed in a chamber and forced through a die opening by a ram.
The die may be round or of various other shaped
->Typical parts made are railings for sliding doors, window frames, aluminium ladders
,tubing and structural and architectural shapes
->It may be defined as the manufacturing process in which a block of metal enclosed
in a container is forced to flow through the opening of a die.The metal is subjected to
plastic deformation and it undergoes reduction and elongation during extrusion.The
section of the product will depend upon the shape of the die opening.
->manufacture of solid ,hollow sections from non-ferrous metals and their alloys(Al
alloy, Co,brass)
->steel and other ferrous metal can also processed in a hot extrusion and using
molten glass lubricants
->two type -hot extrusion
-cold extrusion
->4 basic types of extrusion
109. Direct Extrusion (Forward Extrusion)
• ->it is similar to forcing toothpaste through a opening of a tube
• ->note that the billet in this process slides relative to the
container wall
• ->At the end of extruding operation a small piece of
metal,called butt-end scrap,remaning in the container and cannot be extruded.
• ->But in forging scrap ie flash comes out of the die, but in extrusion parts come out die product
110.
111. b)Indirect Extrusion (Reverse ,Inverted,
Backward)
->Here the die moves towards the billet and there is no relative motion of the billet-container
interface
,except the
die
Comparison
->In the direct extrusion, when the ram moves the billet must slide the interface b/w billet and the
container. These large friction forces must be overcome by very high ram forces which produce
very high residual stresses on the container.
->But in the indirect extrusion ,the billet does not move relative to the container ,instead the die
moves. The friction involved is only b/w the die and the billet and this is independent of the billet
length
->Extrusion ratio
Ratio of cross-sectional area of the billet to the cross-section area of the product. It is 40:1
for hot extrusion of steel and may be as high as 400:1 for Al
112.
113. Metal flow in extrusion
It depends on
1)Friction at billet-container interface and billet-die
interface 2)thermal gradients within the billet
->The most homogeneous(uniform) flow pattern is obtained when
there is no friction at the interface.This type of flow occuresd when
the lubricant is very effective or indirect extrusion where there is no
friction at the billet- container interfaces
Dead zone
->when the friction along all the interfaces is high, a dead-metal zone
develops
->note the high-shear area as the metal flows into the die exist
->In the third config the high shear zone extends further back into the billet
->In the hot extrusion, the metal near the container walls cools
rapidly,there by metal becomes stronger : as a result ,the metal in the
central region of the billet flows towards the die more easily than that at
115. ->Drawing operation in which the cross sectional area of a bar or tube is reduced or changed in
shape by pulling it throughout a converging die
->In drawing the bar is under tension but in extrusion the bar is under compression (Rod or wire)
->It is a finishing process or is further processed in to other shapes by bending or melting
->Small pistons,shafts,spindles,raw metal for making fastners such as bolts and screws.
->Wire and wire products have a wide range of operations such as electrical wiring (dia
0.025mm),electronic equipments,cavles,springs,musicalinstruments,
paper clips,fencing,welding electrodes etc.
117. 1. SOLDERING
• Method of joining two or more metal pieces by means ofa
fusible alloy or metal called solder(filler alloy), applied in
molten state
• The melting temperature of filler metal is lower than 450°C
and also lower than the melting point of the components to
be joined
118. • No direct melting of the metals beingjoined
• During the process, the filler alloy(solder) flows between
the two closely adjacent surfaces of the work pieces by
capillary action
• Solder is melted by using a soldering iron, which isheated
by electrical resistance
• Soldering iron tips are made of copper core platedwith
iron. The copper is used for heat transfer and the iron
plating is used for durability
119.
120.
121.
122. 2. BRAZING
• Metal pieces are joined by heating the closely placedparts
and then filler alloy called spelter applied in the molten
state which upon solidification produces the desiredjoint
• Melting temperature of filler metal is more than 450°C but
lower than the melting temperature of the components to
be joined
123. • No direct melting of the metals beingjoined
• Brazing gives a much stronger joint compared to soldering
• During the process, the filler alloy(spelter) flows between
the two closely adjacent surfaces of the work pieces by
capillary action
• Torch brazing is the most versatile method
(Oxygen-Acetylene)
128. 3. WELDING
• Process of joining similar or dissimilar metals by the
application of heat, with or without the application of
pressure and with or without the addition of fillermaterial
Two types
• Plastic welding
• Fusion welding
129. • Plastic welding: metals to be joined are to be heated tothe
plastic state and then forced together by external pressure
without the addition of filler material. Eg. forgewelding,
resistance welding…etc
• Fusion welding: no pressure is involved but a very high
temperature is produced in or near the joint. The metal at
the joint is heated to the molten state and allowed to
solidify. A filler material may be used during the welding
process. Eg. Oxy-acetylene welding, carbon arc welding…etc
131. GAS WELDING
• Welding process that uses a fuel gas combined with oxygen
to produce a flame
• Fusion welding process
• It joins metals using the heat of combustion ofoxygen/air
and fuel gas(acetylene, hydrogen, propane or butane)
132. RESISTANCE WELDING
• Parts to be joined are heated to a plastic state over a limited
area by their resistance to flow of electric current(resistance
heating) and then by mechanically pressingtogether
• Pressure is applied continuously till the weld coolsdown
• It is generally used for joining thin plates and structures
134. ARC WELDING
• Method of fusion welding in which the metals at the joint
is heated to molten state by an electric arc
• Arc column is generated between an anode(electrode) and
the cathode(metal to be joined)
• Temperature of the arc is about 6000⁰C to 7000⁰C
135. ELECTRODES
• Non- consumable electrodes: carbon, graphiteor
tungsten(they are not consumed during weldingoperation)
• Consumable electrodes: steel(consumed during welding
operation), electrode may be bare(uncoated) or fluxcoated
137. How an arc is
formed?
• The arc is like a flame
of intense heat that is
generated as the
electrical current
passes through a
highly resistant air
gap.
139. Arc Welding
• It is a fusion welding processes which
uses an electric arc to produce the heat
required for melting the metal.
• The welder creates an electric arc that melts the base
metals and filler metal (consumable) together so that
they all fuse into one solid piece of metal
140. Arc Welding
• Many things around usare welded…
– Pipelines that bring fresh water
– Towers that carry electricity to houses
– Cars and buses that take people where they need to go
• Arc welding continues to be used extensively in the
construction of steel structures and in industrial fabrication.
• The process is used primarily to weld iron and steels
(including stainless steel) but aluminium, nickel and copper
alloys can also be welded with this method.
• It dominates other welding processes in the maintenance
and repair industry, and though flux-cored arc welding is
growing in popularity
• Is popular because it can be used in the field without
complicated equipment and gases
141. Arc Welding
• It is a manual arc welding process that uses a
consumable electrode coated in flux to lay the
weld.
• An electric current, in the form of either alternating
current or direct current from a welding power
supply, is used to form an electric arc between
the electrode and the metals to be joined.
• As the weld is laid, the flux coating of the
electrode disintegrates, giving off vapors that
serve as a shielding gas and providing a layer of
slag, both of which protect the weld area from
atmospheric contamination.
142. Arc Welding
• Arc welding is a process that melts and joins metals
by heating them with an arc established between a
sticklike covered electrode and the metals.
• The core wire conducts the electric current to the arc
and provides filler metal for the joint.
• The electrode holder is essentially a metal clamp
with an electrically insulated outside shell for the
welder to hold safely.
• The heat of the arc melts the core wire and the
flux covering at the electrode tip into metal
droplets.
• Molten metal in the weld pool solidifies into the weld
metal while the lighter molten flux floats on the top
surface and solidifies as a slag layer.
144. Principle of Arc
• A suitable gap is kept between the work
and electrode
• A high current is passed through the
circuit.
• The electric energy is converted into heat
energy, producing a temperature of
3000°C to 4000°C.
• This heat melts the edges to be welded
and molten pool is formed.
• On solidification the welding joint is
145. Arc Welding
• Process:
– Intense heat at the arc melts the tip of the electrode
– Tiny drops of metal enter the arc stream and are
deposited on the parent metal
– As molten metal is deposited, a slag forms over the
bead which serves as an insulation against air
contaminants during cooling
– After aweld ‘pass’ is allowed the cool, the oxide layer is
removed by a chipping hammer and then cleaned
with a wirebrush before the next pass.
146. Arc Welding
• Because of the versatility of the process
and the simplicity of its equipment and
operation, shielded metal arc welding is
one of the world's most popular welding
processes.
149. Basic Steps of Arc Welding
• Prepare the base materials: remove paint
and rust
• Choose the right welding process
• Choose the right filler material
• Assess and comply with safety requirements
• Use proper welding techniques and be sure
to protect the molten puddle from
contaminants in the air
• Inspect the weld
150. ARC WELDING
• An electric arc is generated
between an electrode and the
parent metal
• The electrode carries the electric current
to form the arc, produces a gas to
control the atmosphere and provides
filler metal for the weld bead
• Electric current may be AC or DC.
151. Comparison of A.C. and D.C. arc
welding Direct Current (from
Generator)1. Less efficiency
2. Power consumption more
3. Cost of equipment is more
4. Low voltage –safer operation
5. Suitable for both ferrous non ferrous metals
6. Preferred for welding thin sections
7. Positive terminal connected to the work
8. Negative terminal connected to the electrode
153. Arc Welding Defects
The most common quality problems associated with SMAW
include
• 1. Weld spatter
Weld spatter, while not affecting the integrity of the weld,
damages its appearance and increases cleaning costs. It can
be caused by excessively high current, a long arc, or arc
blow, a condition associated with direct current characterized
by the electric arc being deflected away from the weld pool by
magnetic forces. Arc blow can also cause porosity in the
weld, as can joint contamination, high welding speed, and a
long welding arc, especially when low-hydrogen electrodes
are used.
• 2. Porosity
Porosity, often not visible without the use of advanced
nondestructive testing methods, is a serious concern because
it can potentially weaken the weld.
154. Arc Welding Defects
• 3. Poor fusion
Another defect affecting the strength of the weld is poor
fusion, though it is often easily visible. It is caused by low
current, contaminated joint surfaces, or the use of an
improper electrode.
• 4. Shallow penetration
Shallow penetration, another detriment to weld strength, can
be addressed by decreasing welding speed, increasing the
current or using a smaller electrode.
• 5. Cracking.
Any of these weld-strength-related defects can make the
weld prone to cracking, but other factors are involved as
well. High carbon, alloy or sulfur content in the base
material can lead to cracking, especially if low-hydrogen
electrodes and preheating are not employed. Furthermore,
the workpieces should not be excessively restrained, as this
introduces residual stresses into the weld and can cause
cracking as the weld cools and contracts.
155. Advantages of arc welding
• 1. Simple welding equipment
• 2. Portable
• 3. Inexpensive power source
• 4. Relatively inexpensive equipment
• 5. Welders use standard domestic current.
• 6. Process is fast and reliable
• 7. Short learning curve
• 8. Equipment can be used for multiple functions
• 9. Electric arc is about 5,000 oC
• 10. Used for maintenance, repair, and field
construction
156. Disadvantages
• Not clean enough for reactive metals
such as aluminium and titanium.
• The deposition rate is limited because
the electrode covering tends to overheat
and fall off.
• The electrode length is ~ 35 mm and
requires electrode changinglower the
overall production rate.
157. Flux-Cored Arc Welding (FCAW)
• Uses an arc between a continuous filler
metal electrode and a workpiece
• Shielding is provided by a flux contained
within the electrode
• Additional shielding may be obtained from
an externally supplied gas or gas mixture
• Commonly used in construction because it
is a fast welding process and is easily
portable
161. • The heat is generated by an electric arc between base
metal and a consumable electrode.
• In this process electrode movement is manuallycontrolled
hence it is termed as manual metal arcwelding
• In shielded metal arc welding, the protection to the weld
pool is provided by covering of a) slag formed over the
surface of weld pool/metal and b) inactive gases generated
through thermal decomposition of flux/coating materials on
the electrode
162. • This process can use both AC and DC. The constantcurrent
DC power source is invariably used with all types of
electrode irrespective of base metal (ferrous and non-
ferrous)
• AC can be unsuitable for certain types of electrodes and base
materials
• SHIELDED METAL ARC WELDING welding normally uses
constant current type of power source with weldingcurrent
50-600A and voltage 20-80V
• Welding current (A) is generally selected in range of 40-60
times of electrode diameter (mm)
170. Milling Processes
Operations that create flat or curved
surfaces by progressively removing
material
Cutting tools rotate as the work piece is
secured and fed into the tool
Machining Processes
174. Machining
A material removal process in which a sharp cutting tool
is used to mechanically cut away material so that the
desired part geometry remains
• Most common application: to shape metal parts
• Machining is the most versatile and accurate of all
manufacturing processes in its capability to produce
a diversity of part geometries and geometric features
Casting can also produce a variety of shapes, but
it lacks the precision and accuracy of machining
175. Classification of Machined Parts
1. Rotational - cylindrical or disk-like shape
2. Nonrotational (also called prismatic) - block-like or
plate-like
Figure 22.1 - Machined parts are classified as: (a) rotational, or (b)
nonrotational, shown here by block and flat parts
176. Machining Operations and Part Geometry
Each machining operation produces a characteristic part
geometry due to two factors:
1. Relative motions between the tool and the
workpart
• Generating – part geometry is determined by
the feed trajectory of the cutting tool
2. Shape of the cutting tool
• Forming – part geometry is created by the
shape of the cutting tool
178. Figure 22.3 - Forming to create shape: (a) form turning, (b) drilling,
and (c) broaching
179. Figure 22.4 - Combination of forming and generating to create
shape: (a) thread cutting on a lathe, and (b) slot milling
180. Turning
A single point cutting tool removes material from a
rotating workpiece to generate a cylindrical shape
• Performed on a machine tool called a lathe
• Variations of turning that are performed on a lathe:
Facing
Contour turning
Chamfering
Cutoff
Threading
183. Contour Turning
Instead of feeding the tool parallel to the axis of rotation, tool follows a
contour that is other than straight, thus creating a contoured form
Figure (c) contour turning
185. Cutoff
Tool is fed radially into rotating work at some location to cut
off end of part
Figure (f) cutoff
186. Threading
Pointed form tool is fed linearly across surface of rotating
workpart parallel to axis of rotation at a large feed rate,
thus creating threads
Figure (g) threading
193. Figure 22.9 - (a) Part produced on a six-spindle automatic bar
machine; and (b) sequence of operations to produce the part: (1)
feed stock to stop, (2) turn main diameter, (3) form second
diameter and spotface, (4) drill, (5) chamfer, and (6) cutoff
194. Boring
• Difference between boring and turning:
Boring is performed on the inside diameter of an
existing hole
Turning is performed on the outside diameter of
an existing cylinder
• In effect, boring is an internal turning operation
• Boring machines
Horizontal or vertical - refers to the orientation of
the axis of rotation of machine spindle
195. Figure 22.12 - A vertical boring mill –for large, heavy workparts
196. Drilling
• Creates a round hole in
a workpart
• Contrasts with boring
which can only enlarge
an existing hole
• Cutting tool called a drill
or drill bit
• Customarily performed
on a drill press Figure 21.3 (b) drilling
197. Through Holes vs. Blind Holes
Through-holes - drill exits the opposite side of work
Blind-holes – drill does not exit work on opposite side
Figure 22.13 - Two hole types: (a) through-hole, and (b) blind hole
198. Reaming
Used to slightly
enlarge a hole,
provide better
tolerance on
diameter, and
improve surface
finish
Figure 22.14 -
Machining operations
related to drilling:
(a) reaming
200. Counterboring
Provides a stepped hole,
in which a larger
diameter follows a
smaller diameter
partially into the hole
Figure 22.14 (c) counterboring
201. Upright Drill
Stands on the floor
Bench Drill
Similar but smaller
and mounted on
a table or bench
Figure 22.15 - Upright drill press
203. Work Holding for Drill Presses
• Workpart can be clamped in a vise, fixture, or jig
Vise - general purpose workholder with two jaws
Fixture - workholding device that is usually
custom-designed for the particular workpart
Drill jig – similar to fixture but also provides a
means of guiding the tool during drilling
204. Milling
Machining operation in which work is fed past a rotating
tool with multiple cutting edges
• Axis of tool rotation is perpendicular to feed direction
• Creates a planar surface; other geometries possible
either by cutter path or shape
• Other factors and terms:
Milling is an interrupted cutting operation
Cutting tool called a milling cutter, cutting edges
called "teeth"
Machine tool called a milling machine
205. Figure 21.3 - Two forms of milling:
(a) peripheral milling, and (b) face milling
206. Peripheral Milling vs. Face
Milling
• Peripheral milling
Cutter axis is parallel to surface being machined
Cutting edges on outside periphery of cutter
• Face milling
Cutter axis is perpendicular to surface being milled
Cutting edges on both the end and outside
periphery of the cutter
207. Slab Milling
The basic form of peripheral milling in which the cutter
width extends beyond the workpiece on both sides
Figure 22.18
(a) slab milling
208. Slotting
• Width of cutter is less than workpiece width, creating
a slot in the work
Figure 22.18
(b) slotting
210. End Milling
Cutter diameter is less
than work width, so a
slot is cut into part
Figure 22.20 - (c) end milling
211. Profile Milling
Form of end milling in
which the outside
periphery of a flat part is
cut
Figure 22.20 (d) profile milling
212. Pocket Milling
Another form of end milling
used to mill shallow
pockets into flat parts
Figure 22.20 (e) pocket milling
213. Surface Contouring
Ball-nose cutter is fed back and
forth across the work along a
curvilinear path at close
intervals to create a three
dimensional surface form
Figure 22.20 (f) surface contouring
216. Figure 22.24 (b) ram type knee-and-column machine; ram can
be adjusted in and out, and toolhead can be swiveled
217. *A numerical control
system in which the
data
handling, control
sequences, and
response to input is
determined by an on-
board computer
system at the
machine tool.
*
218. CNC Machines- How do they look like?
Slides
Controller
Servo Motors
Display Console
Controller
Automated
Tool changer
Coolant
control
Chip collection and
removal
219. *
*A CNC machine consist of following 6 major
elements:
i. Input Device
ii. Machine Control Unit
iii. Machine Tool
iv. Driving System
v. Feedback Devices
vi. Display Unit
221. *
In open loop systems the slide may overshoot or may not reach
desired position because of inertia, wear and tear and
friction, hence inaccurate machining.
In closed loop systems the position sensors are used to correct
slide movements and achieve higher accuracy and repeatability
222. *
*Controlled by G and M codes.
*These are number values and co-ordinates.
*Each number or code is assigned to a particular operation.
*Typed in manually to CAD by machine operators.
*G & M codes are automatically generated by the computer
software.
223. *
*The tool or material moves automatically.
*Tools can operate in 1-5 axes.
*Larger machines have a machine control unit (MCU) which
manages operations.
*Movement is controlled by motors (actuators).
*Feedback is provided by sensors (transducers)
*Tool magazines are used to change tools automatically.
224. *
*CNC instructions are called part program commands.
*When running, a part program is interpreted one
command line at a time until all lines are completed.
*Commands, which are also referred to as blocks, are
made up of words which each begin with a letter
address and end with a numerical value.
225. *
Important things to know:
*Coordinate System
*Units, incremental or
absolute positioning
*Coordinates: X,Y,Z, RX,RY,RZ
*Feed rate and spindle speed
*Coolant Control:
On/Off, Flood, Mist
*Tool Control: Tool and tool
parameters
Programming consists of a series
of instructions in form of letter codes
•Preparatory Codes:
G codes- Initial machining setup and
establishing operating conditions
N codes- specify program line number
to executed by the MCU
•Axis Codes: X,Y,Z
Used to specify motion of the slide along
X, Y
,Z direction
•Feed and Speed Codes: F and S
Specify feed and spindle speed
•Tool codes: T – specify tool number
•Miscellaneous codes – M codes
For coolant control and other activities
227. *
* O - Program number (Used for program identification)
* N - Sequence number (Used for line identification)
* G - Preparatory function
* X - X axisdesignation
*Y - Y axis designation
* Z - Z axisdesignation
* R - Radiusdesignation
* F – Feed ratedesignation
* S - Spindle speed designation
* H - Tool length offset designation
* D - Tool radius offset designation
* T - ToolDesignation
* M - Miscellaneous function
229. *
*M00 Program stop
*M01 Optional program stop
*M02 Program end
*M03 Spindle on clockwise
*M04 Spindle on counterclockwise
*M05 Spindle stop
*M06 Tool change
*M08 Coolant on
*M09 Coolant off
*M10 Clamps on
*M11 Clamps off
*M30 Program stop, reset to start
230. Advantages of CNC
i. - Easier to program;
ii. - Easy storage of existing programs;
iii. - Easy to change a program
iv. - Avoids human errors
v. - CNC machines are safe to operate
vi. - Complex geometry is produced as cheaply as simple ones
vii. - Usually generates closer tolerances than manual machines
231. *
i. Costly setup, skilled operators
ii. Computers, programming
knowledge required
iii.Maintenance is difficult
232. What is Additive Manufacturing?
2
3
The process of joining materials to make objects from three-
dimensional (3D) model data, usually layer by layer
Commonly known as “3D printing”
Manufacturing components with virtually no geometric limitations or
tools.
AM uses an additive process
Design for manufacturing to manufacturing for design
Distinguished from traditional subtractive machining techniques
233. Functional principle
The system starts by applying a thin layer of the powder material to the
building platform.
A powerful laser beam then fuses the powder at exactly the points
defined by the computer-generated component design data.
Platform is then lowered and another layer of powder is applied.
Once again the material is fused so as to bond with the layer below at
the predefined points. 5
234. ADVANTAGES
Freedom of design
Complexity for free
Potential elimination of tooling
Lightweight design
Elimination of production steps
DISADVANTAGES
Slow build rates
High production costs
Considerable effort required for application design
Discontinuous production process
Limited component size.
235. Applications
Additive Manufacturing has been used
across a diverse array of industries,
including;
Automotive
Aerospace
Biomedical
Consumer goods and many others
236. CAD and CAM generally stands for Computer aided
Design and Computer aided manufacturing
Respectively. Designing usually starts with CAD
software where actual drawing of the part to be
machined is made which is followed bygenerating
tool paths on CAM software. CAD Technology =
Design Techniques + Computers .The CADProcess
is the subset of the Design process. The CAM
Process is a subset of Manufacturing Process
Integration of CAD and CAM leads toautomation.
237. CAD and Cam (Computer Aided Manufacturing) together create
a link between product design andmanufacturing.
The CAD system is used to develop a geometric model of the part
which is then used by the CAM system to generate part programs
for CNC machinetools.
Both CAD and CAM functions may be performed eitherby the
same system or separate systems in different rooms or even
countries.
A computer aided design, or CAD, system uses computers to
graphically createproduct designsand models. Thesedesignscan
be reviewed, revised, and refined for optimum end use and
application. Once finalized, the CAD design is then exported toa
computer aided manufacturing, or CAM,system.
CAM systems assist in all phases of manufacturing a product,
including process planning, production planning, machining,
scheduling, management and qualitycontrol.
238. Computer Aided Design (CAD): Is defined as the
application of computer and graphics software to
aid the product design from conceptualization to
documentation.
239. Computer Aided Manufacturing: Is defined as the
effective use of computers in manufacturing planning
and control.
240. Twotypes of activities: synthesis and analysis.
Synthesis is largelyqualitativeand hard tocaptureon
computer.
Analysiscan begreatlyenhanced with computers.
Onceanalysis is complete, design evaluation- rapid
prototyping.
Software packages for designoptimization.
241. Product is conceived byengineer.
Product is designed using CADsoftware.
CAD data is transferred to manufacturingmachine’s
memory.
Machine uses the CAD data toproduce the product,
with little humanintervention.
242.
243. • Toincrease productivity of thedesigner.
• Toimprove quality of thedesign.
• Toimprovecommunications.
• Tocreate a manufacturingdatabase.
• Tocreateand test tool pathsand optimize them.
• Tohelp in production scheduling and MRPmodels.
• Tohave effective shop floorcontrol.
245. Automotive Industry.
Aerospace and aircraftindustry.
Textile industry.
Medical industry.
Video gaming industry.
Tool and Die Manufacturing industry.
Welding and Cutting industry.
246. CAD/CAM systems allow forrapid development and
modifying of designs anddocumentation.
It Lowers the overheadcosts.
The coupling of CAD and CAM considerably shortensthe
time needed to bring a new product tomarket.
Increased productivity is generally the justificationfor
using CAD/CAM system.
It gives us Error freedrafting.
247. Expensive Software.
Special skillsrequired.
Expensive machinesrequired.
High Maintenance.
Nature of material of theobject.
