Production engineering

Introduction to Cutting - Common
Machining Operations
Figure 21.1 Some examples of common machining
operations.
Cutting processes remove material
from the surface of a workpiece by
producing chips.
Turning, in which the workpiece is rotated
and a cutting tool removes a layer of
material as the tool moves to the left.
Cutting off: in which the cutting tool
moves radially inward and separates the
right piece from the bulk of the blank.
Slab milling: in which a rotating cutting
tool removes a layer of material from the
surface of the workpiece.
End milling: in which a rotating cutter
travels along a certain depth in the work-
piece and produces a cavity.

OBJECTIVE OF METAL
CUTTING
• Quick material removal
• High class surface finish
• Economy in tool cost
• Less power consumption
• Minimum ideal time to machine tool

Basic element of machining
• Work piece
• Tool
• Chip

Orthogonal and oblique cutting
The process of metal cutting is divided in to
following two main classes
• Orthogonal cutting
• Oblique cutting

Comparison between orthogonal and
oblique cutting

Orthogonal cutting Oblique Cutting
The cutting edge of the tool is perpendicular to
the direction of feed motion.
The cutting edge of the tool is inclined to the
direction of feed motion
Chip flow is expected to in a direction
perpendicular to the cutting edge
The chip flow angle is more than zero.
There are only two components of force; these
components are mutually perpendicular.
There are three mutually perpendicular forces
acting while cutting proces
The cutting edge is larger than cutting width The cutting edge may or may not be larger
than cutting width.
Chips are in the form of a spiral coil Chip flow is in a sideways direction
High heat concentration at cutting region Less concentration of heat at cutting region
compared to orthogonal cutting
For a given feed and depth of cutting, the force
acts on a small area as compared with oblique
cutting, so tool life is less
Force is acting on a large area, results in more tool life.
Surface finish is poor
Good surface finish obtained.
Used in grooving, parting, slotting, pipe cutting Used almost all industrial cutting, used in
drilling, grinding, milling.

Classification of cutting tools
All cutting tool used in metal cutting can
broadly classified as
• Single point tools,i.e., those having only one
cutting edge; such as lathe tools, shaper tools,
planer tools, boring tools.
• Multi-point tools,i.e.,those having more than
one cutting edge; such as milling cutter, drills,
grinding wheel ,etc.

Classification of cutting tools
• The cutting tools can also be classified
according to motion as
• Linear motion tools; lathe, boring, broaching,
planing, shaping tools, etc.
• Rotary motion tools; milling cutters, grinding
wheels etc.
• Linear and rotary tools; drills, honing tools,
boring heads, etc.

Important term related to geometry
of single point tools
• Shank. It is the main body of solid tool and it is the part of tool
which is gripped in tool holders
• Face . It is the top surface of tool between the shank and point of the
tool. In the cutting action, the chips flow along this surface only.
• Point. It is the wedge shaped portion where the face and flank of the
tool meet. it is the cutting part of the tool. It is also called nose,
• Flank. Portion of the tool which faces the work is termed as flank.
• Base. It is actually the bearing surface of tool on which it is held in a
tool post.
• Heel. It is the curved portion at the bottom of tool where the base
and flank of tool meet.
• Nose radius. It is the cutting tip(nose) of single point tool carries a
sharp cutting point, the cutting tip is weak. In order to prevent these
harmful effect nose is provide with radius called nose radius

Principle angle of single point tool
• Rake angle
• Lip angle
• Clearance angle
• Relief angle
• Cutting angle

CHIP FORMATION
TYPES OF CHIPS
• DISCONTINUOUS OR SEGMENTAL
CHIPS
• CONTINUOUS CHIP

DISCONTINUOUS OR
SEGMENTAL CHIPS
• This type of chips are produced during machining of
brittle materials like cast iron and bronze.
• These chip are produced in the form of small segments.
• In machining of such materials, as the tool advances
forward, the shear plane angle gradually reduces until
the value of compressive stress acting on shear plane
become too low to prevent rapture.
• At this stage, any further advancement of tool results in
the fracture of metal ahead of it, thus producing a
segment of chip.

DISCONTINUOUS OR
SEGMENTAL CHIPS
• Further advancement of tool, the processes of
metal fracture and production of chip segments go
on being repeated, and this is how the
discontinuous chips are produced
• Such chips are also sometimes produced in the
machining of ductile materials when low cutting
speeds are used and adequate lubrication is not
provided.
• This causes excessive friction between the chip
and tool face, leading to the fracture of chip into
small segments.

OTHER FACTORS RESPONSIBLE
FOR DISCONTINUOUS CHIPS
• SMALLER RAKE ANGLE ON TOOL
• TOO MUCH DEPTH OF CUT

CONTINUOUS CHIP
• Continuous type of chip is produced while
machining a ductile materials, like mild
steel,under favorable cutting conditions, such
as high cutting speed and minimum friction
between the chip and tool face. Otherwise, it
will break and form the segmental chip.
• The friction at the chip-tool interface can be
minimized by polishing the tool face and
adequate use of coolant.

OTHER FACTOR RESPONSIBLE
FOR CONTINUOUS CHIPS
• BIGGER RAKE ANGLE
• FINER FEED
• KEEN CUTTING EDGE

CONTINUOUS CHIP WITH
BUILT-UP EDGE
• Such a chip is usually formed while machining ductile
material, when high friction exists at the chip tool
interface.
• The upward flowing chip exerts pressure on the tool
face. the normal reaction of the chip on the tool face is
quite high, and is maximum at the cutting edge or nose
of the tool.
• This gives rise to an excessively high temperature and
the compressed metal adjacent to the tool nose gets
welded to it.
• This extra metal welded to the nose or point of tool is
called built up edge.

CONTINUOUS CHIP WITH
BUILT-UP EDGE
• This metal is highly strain hardened and
brittle. With the result, as the chip flows up
the tool, the built-up edge is broken and
carried away with chip while the rest of it
adheres to the surface of work piece, making
it rough.

ADVERSE EFFECTS OF BUILT-
UP EDGE
• ROUGH SURFACE FINISH ON WORKPIECE
• FLUCTUATING CUTTING FORCE,CAUSING
VIBRATION IN CUTTING TOOL
• CHANCES OF CARRYING AWAY SOME
MATERIAL FROM THE TOOL BY BUILT-UP
SURFACE,PRODUCING CRATER ON TOOL
FACE AND CAUSING TOOL WEAR.

AVOIDING THE FORMATION OF
BUILT-UP EDGE FORMATION
• The coefficient of friction at the chip-tool
interface should be minimized by means of
polishing the tool face and adequate supply of
coolant during the operation.
• The rake angle should be kept large.
• High cutting speeds and low feeds should be
employed.

CHIP THICKNESS RATIO
• During the cutting action of metal it will be
observed that the thickness of deformed or
upward flowing chip is more than the actual depth
of cut.
• It is because the chip flows upwards at slower rate
than the velocity of cut.
• The velocity of the chip flow is directly affected
by the shear plane angle.
• The smaller this angle the slower will be the chip-
flow velocity and, therefore, larger will be the
thickness of chip.

• Chip thickness ‘r’ is given by
…… 1
• Chip reduction coefficient ’k’
………2

• Product of thickness and length of metal cut.
• …….3
• Two right angle triangles OAP and OBP

• Considering right angle triangle OAP, we have:
• ( AP=t1)
• ……..4
• Considering the right angle triangle OBP, we have

• …………5

• Comparing eq. 4&5 for OP, we get
•

Mechanics of Cutting
Velocities in the Cutting Zone
• Since tc > to ⇒ Vc (velocity of chip) < V (cutting speed)
• Since mass continuity is maintained,
• From Velocity diagram, obtain equations from
trigonometric relationships (Vs velocity at shearing
plane):
• Note also that
 



cos
sin
or0
V
VVrVtVVt cccc
   sincoscos
cs VVV


V
V
t
t
r c
c
 0
35

Cutting Forces and Power
• Knowledge of cutting forces and power involves:
1. Data on cutting forces
– important to minimize distortions, maintain required
dimensional accuracy, help select appropriate toolholders
2. Power requirements
– enables appropriate tool selection
Copyright © 2010 Pearson Education South Asia Pte Ltd
36
Forces acting in
the cutting zone
during 2-D (orthogonal)
cutting
Force circle to
determine
various forces in
cutting zone

• Forces considered in orthogonal cutting include
– Cutting, friction (tool face), and shear forces
• Cutting force,Fc acts in the direction of the cutting
speed V, and supplies the energy required for cutting
– Ratio of Fc to cross-sectional area being cut (i.e. product of
width and depth of cut, t0) is called: specific cutting force
• Thrust force,Ft acts in a direction normal to the cutting
force
• These two forces produces the resultant force, R
– see force circle (last slide)
• On tool face, resultant force can be resolved into:
– Friction force, F along the tool-chip interface
– Normal force, N to  to friction force37

• It can also be shown that ( is friction angle)
• Resultant force, R is balanced by an equal and
opposite force along the shear plane
• It is resolved into shear force, Fs and normal force, Fn
• Thus,
• The magnitude of coefficient of friction,  is
 cossin RNRF 


cossin
sincos
tcn
tcs
FFF
FFF





tan
tan
tc
ct
FF
FF
N
F



38

Thrust Force
• The toolholder, work-holding devices, and machine tool
must be stiff to support thrust force with minimal
deflections
– If Ft is too high ⇒ tool will be pushed away from workpiece
– this will reduce depth of cut and dimensional accuracy
• The effect of rake angle and friction angle on the direction
of thrust force is
• Magnitude of the cutting force, Fc is always positive as the
force that supplies the work is required in cutting
• However, Ft can be +ve or –ve; i.e. Ft can be upward with
a) high rake angle, b) low tool-chip friction, or c) both
     tanorsin ctt FFRF
39

Power
• The power input in cutting is
• Power is dissipated in
– shear plane/zone (due to energy required to shear material)
– Rake face (due to tool-chip interface friction)
• Power dissipated in shearing is
• Denoting the width of cut as w, (i.e. area of cut: wt0),
the specific energy for shearing, is
VFPower c
ssVFshearingforPower
Vwt
VF
u ss
s
0

40

Power
• The power dissipated in friction is
• The specific energy for friction, uf is
• Total specific energy, ut is
cFVfrictionforPower
00 wt
Fr
Vwt
FV
u c
f 
fst uuu 
41

Measuring Cutting Forces and Power
• Cutting forces can be measured using a force
transducer, a dynamometer or a load cell mounted
on the cutting-tool holder
• It is also possible to calculate the cutting force from the
power consumption during cutting (provided
mechanical efficiency of the tool can be determined)
• The specific energy (u,) in cutting can be used to
calculate cutting forces.
42

EXAMPLE 21.1
Relative Energies in Cutting
In an orthogonal cutting operation, to=0.13 mm, V=120
m/min, α=10° and the width of cut 6 mm. It is observed that
tc=0.23 mm, Fc=500 N and Ft=200 N. Calculate the
percentage of the total energy that goes into overcoming
friction at the tool–chip interface.
44

Solution
The percentage of the energy can be expressed as
where
We have
cc
c
F
Fr
VF
FV

EnergyTotal
EnergyFriction
565.0
23.0
13.00

ct
t
r
 
  N539500200
andcos,sin
2222


ct
c
FFR
RFRF 
45

Solution
Thus,
Hence
 
N28632sin539
3210cos539500


F

   %32or32.0
500
565.0286
Percentage 
46

Temperatures in Cutting
• Temperature rise (due to heat lost in cutting ⇒ raising
temp. in cutting zone) - its major adverse effects:
1. Lowers the strength, hardness, stiffness and wear
resistance of the cutting tool (i.e. alters tool shape)
2. Causes uneven dimensional changes (machined parts)
3. Induce thermal damage and metallurgical changes in
the machined surface (⇒ properties adversely affected)
• Sources of heat in machining:
a. Work done in shearing (primary shear zone)
b. Energy lost due to friction (tool-chip interface)
c. Heat generated due to tool rubbing on machined surface
(especially dull or worn tools)
47

• Expression: mean temperature in orthogonal cutting:
where,
– T: (aka Tmean) mean temperature in [K]
– Yf: flow stress in [MPa]
– ρc: volumetric specific heat in [kJ/m3·K]
– K: thermal diffusivity (ratio of thermal conductivity to
volumetric specific heat) in [m2/s]
– Equation shows that T:
• increases with material strength, cutting speed (V), depth of cut (t0);
• decreases with ρc and K
3 0
000665.0
K
Vt
c
Y
T
f


48

• Mean temperature in turning on a lathe is given by
where,
– V : cutting speed
– f : feed of the tool
– Approximate values of the exponents a,b:
• Carbide tools: a = 0.2, b = 0.125
• High-speed steel tools: a = 0.5, b = 0.375
– Also note how this relation shows the increase in
temperature with increased cutting speed and feed
ba
mean fVT 
49

Temperature Distribution
• The temperature increases with cutting speed
• Chips can become red hot and create a safety hazard
for the operator
• The chip carries away most (90%) of the heat
generated during machining (see right)
– Rest carried by tool and workpiece
• Thus high machining speed (V ) ⇒
1. More energy lost in chips
2. Machining time decreases
(i.e. favorable machining economics)
50

Techniques for Measuring Temperature
• Temperatures and their distribution can be determined
using
– thermocouples (placed on tool or workpiece)
– Electromotive force (thermal emf) at the tool-chip interface
– Measuring infrared radiation (using a radiation pyrometer)
from the cutting zone (only measures surface temperatures)
51

Tool Life: Wear and Failure
• Tool wear is gradual process; created due to:
1. High localized stresses at the tip of the tool
2. High temperatures (especially along rake face)
3. Sliding of the chip along the rake face
4. Sliding of the tool along the newly cut workpiece
surface
• The rate of tool wear depends on
– tool and workpiece materials
– tool geometry
– process parameters
– cutting fluids
– characteristics of the machine tool
52

• Tool wear and the changes in tool geometry are
classified as:
a) Flank wear
b) Crater wear
c) Nose wear
d) Notching
e) Plastic deformation of the tool tip
f) Chipping and Gross fracture
53

54
a) Features of tool wear in a turning operation. VB: indicates average flank wear
b) – e) Examples of
wear in cutting
tools
b) Flank
wear
c) Crater
wear
d) Thermal
cracking
e) Flank
wear and
built-up edge
(BUE)

Tool Life: Wear and Failure:
Flank Wear
• Flank wear occurs on the relief (flank) face of the tool
• It is due to
– rubbing of the tool along machined
surface (⇒ adhesive/abrasive wear)
– high temperatures (adversely
affecting tool-material properties)
• Taylor tool life equation :
CVTn

V = cutting speed [m/minute]
T = time [minutes] taken to develop a certain flank wear land (VB, last slide)
n = an exponent that generally depends on tool material (see above)
C = constant; depends on cutting conditions
note, magnitude of C = cutting speed at T = 1 min (can you show how?)
Also note: n, c : determined experimentally
55

Flank Wear
Tool-life Curves
• Tool-life curves are plots of experimental data from
performing cutting tests on various materials under
different cutting conditions (e.g. V, f, t0, tool material,…)
• Note (figure below)
– As V increases ⇒ tool life decreases v. fast
– Condition of work piece material has large impact on tool life
– There’s large difference in tool life among different compositions
56
Effect of workpiece hardness and
microstructure on tool life in
turning ductile cast iron. Note the
rapid decrease in tool life
(approaching zero as V increases).

Crater Wear
• Factors influencing crater wear are
1. Temperature at the tool–chip interface
2. Chemical affinity between tool and workpiece materials
• Crater wear occurs due to “diffusion mechanism”
– This is the movement of atoms across tool-chip interface
– Since diffusion rate increases with increasing temperature,
⇒ crater wear increases as temperature increases (see ↓)
– Note how quickly crater wear-rate
increases in a small temperature
range
– Coatings to tools is an effective
way to slow down diffusion process
(e.g. titanium nitride, alum. oxide)
57

Crater Wear
• Location of the max depth of
crater wear, KT, (slide 52)
coincides with the location of the
max temperature at the tool–chip
interface (see right)
– Note, how the crater-wear pattern
coincides with the discoloration
pattern
– Discoloration is an indication of
high temperatures
58
Interface of a cutting tool (right)
and chip (left) in machining plain
carbon-steel. Compare this with
slide 46.

Other Types of Wear, Chipping, and Fracture
• Nose wear is the rounding of a sharp tool due to
mechanical and thermal effects
– It dulls the tool, affects chip formation, and causes rubbing of
the tool over the workpiece
– This raises tool temperature, which causes residual stresses
on machined surface
• Tools also may undergo plastic deformation because
of temperature rises in the cutting zone
– Temp. may reach 1000 ºC (or higher in stronger materials)
• Notches or grooves occur at boundary where chip no
longer touches tool
– Boundary is called depth- of-cut (DOC) line with depth VN
– Can lead to gross chipping in tool (due to small area)59

Factor affecting tool life
• Cutting speed
• Tool geometry
• Work materials
• Rigidity of machine tool
& work.
• Feed and depth of cut
• Tool materials
• Nature of cutting
• Use of cutting fluids.

Types of cutting materials
• High carbon steel
• Coated H.S.S
• Satellite
• High speed steel
• Cemented carbide
• Cemented oxides or ceramics
• Diamond

Characteristics of a Good Cutting
Fluid
1. Good cooling
capacity
2. Good lubricating
qualities
3. Resistance to
rancidity
4. Relatively low
viscosity
5. Stability (long life)
6. Rust resistance
7. Nontoxic
8. Transparent
9. Nonflammable
62

Types of Cutting Fluids
• Most commonly used cutting fluids
– Either aqueous based solutions or cutting oils
• Fall into three categories
– Cutting oils
– Emulsifiable oils
– Chemical (synthetic) cutting fluids
63

Cutting Oils
• Two classifications
– Active
– Inactive
• Terms relate to oil's chemical activity or
ability to react with metal surface
– Elevated temperatures
– Improve cutting action
– Protect surface
64

Active Cutting Oils
• Those that will darken copper strip immersed
for 3 hours at temperature of 212ºF
• Dark or transparent
• Better for heavy-duty jobs
• Three categories
– Sulfurized mineral oils
– Sulfochlorinated mineral oils
– Sulfochlorinated fatty oil blends
65

Inactive Cutting Oils
• Oils will not darken copper strip
immersed in them for 3 hours at 212ºF
• Contained sulfur is natural
– Termed inactive because sulfur so firmly
attached to oil – very little released
• Four general categories
– Straight mineral oils, fatty oils, fatty and
mineral oil blends, sulfurized fatty-mineral
oil blend
66

Emulsifiable (Water Soluble) Oils
Mineral oils containing soap like material
that makes them soluble in water and
causes them to adhere to work piece
Emulsifiers break oil into minute particles
and keep them separated in water
› Supplied in concentrated form (1-5 /100 water)
Good cooling and lubricating qualities
Used at high cutting speeds, low cutting
pressures
67

Chemical Cutting Fluids
Also called synthetic fluids
Introduced about 1945
Stable, preformed emulsions
› Contain very little oil and mix easily with
water
Extreme-pressure (EP) lubricants added
› React with freshly machined metal under heat
and pressure of a cut to form solid lubricant
Reduce heat of friction and heat caused by
plastic deformation of metal
68

Advantages of Synthetic Fluids
1. Good rust control
2. Resistance to rancidity for long periods
of time
3. Reduction of amount of heat generated
during cutting
4. Excellent cooling qualities
69

5. Longer durability than cutting or soluble
oils
6. Nonflammable - nonsmoking
7. Nontoxic.
8. Easy separation from work and chips
9. Quick settling of grit and fine chips so
they are not recirculated in cooling system
10. No clogging of machine cooling system
due to detergent action of fluid
11. Can leave a residue on parts and tools
70

Functions of a Cutting Fluid
• Prime functions
– Provide cooling
– Provide lubrication
• Other functions
– Prolong cutting-tool life
– Provide rust control
– Resist rancidity
71

Work holding device
• When cutting operations are performed on the
machine, lots of forces are created. To counter
these forces the job and the tool must be held
rigidly so there is no vibration or jerk during
cutting.
• The tool is held rigidly in the tool post with the
assistance of bolts. The work piece is held by
various types of work holding devices depending
on its shape, length, diameter and weight of the
work piece and the location of turning on the
work

The following are the work holding
devices used
1.Chucks
2.Faceplates
3.Drivingplates
4.Carriers
5.Mandrels
6.Centres
7.Rests

Chucks
• Chucks are efficient and
accurate devices for
holding the work on the
lathe during the
operation. The most
common types of chucks
are

Three jaw chucks
• (a) Three Jaw Chucks. It has
three jaws fixed radially to a
cylindrical body at its front, and
it has a hole at its center to
allow long work pieces to
project backward in the
spindle.
• This work holding device is for
holding regular shaped work
pieces such as round or
hexagonal rods about its axis.
The chuck cannot be used for
work pieces of irregular shapes

• Four Jaw Chucks. In outside
appearance, It looks like three jaw
chuck, but its mechanism differs.
Its jaws are threaded and they are
engaged with separate adjusting
screws. So, all the jaws can be
moved separately and adjusted
independently.
• This enables the chuck to
successfully hold irregular or
eccentric work pieces in addition
to the normal cylindrical shaped
jobs. It is also possible to reverse
these same jaws so that the work
piece is gripped from the inside
surfaces

Magnetic Chucks.
• The work piece is held by magnetic forces.

Combination Chucks.
• The features of the three-jaw chuck and
four jaw chuck are combined. The jaws
can be moved in unison or individually if
desired

Face Plates
• It is a cast iron disk
with a threaded hole in
the centre for screwing
onto the nose of the
spindle. It also has a
number of holes and
slots for securing the
work piece

Lathe is one of the oldest important machine tools in the
metal working industry. A lathe operates on the principle of a
rotating work piece and a fixed cutting tool.
 A rope wound round the work with its own end attached to a
flexible branch of tree and other end being pulled by man
caused job to rotate intermittently. With its further
development a strip of wood called “lath” was used to support
the rope and that is how the machine came to be known as
“lathe”.
The cutting tool is feed into the work piece, which rotates
about its own axis, causing the work piece to be formed to the
desired shape.
 Lathe machine is also known as “the mother/father of the
entire tool family”.

 The Lathe Machine is one of the oldest and most
important machine tools. As early as 1569, wood lathes
were in use in France. The lathe machine was adapted to
metal cutting in England during the Industrial Revolution.
Lathe machine also called “Engine Lathe” because the
first type of lathe was driven by a steam engine.

 Henry Maudsley was born on an
isolated farm near Gigghleswick in
North Yorkshire and educated at
University Collage London. He was
an outstandingly brilliant medical
student, collecting ten Gold Medals
and graduating with an M.D. degree
in 1857.

• This term ‘engine’ is associated with the lathe owing to the fact
that early lathes were driven by steam engine. It is also called
centre lathe. The most common form of lathe, motor driven and
comes in large variety of sizes and shapes.

 Engine lathes are classified according to the various designs of
headstock and methods of transmitting power to the machine.
1. Belt Driven Lathe
2. Motor Driven Lathe
3. Gear Head Lathe
 The power to the engine lathe spindle may be given with the help
of a belt drive from an overhead line shaft but most modern
machines have a captive motor with either a cone pulley driven or
an geared headstock arrangement.

• A bench top model usually of low power used to make precision
machine small work pieces.
• It is used for small w/p having a maximum swing of 250 mm at
the face plate. Practically it consists of all the parts of engine
lathe or speed lathe.

• A lathe that has the ability to follow a template
to copy a shape or contour.

 A tool room lathe having
features similar to an engine lathe
is much more accurately built and
has a wide range of spindle speeds
ranging from a very low to a quite
high speed up to 2500 rpm.
 This lathe is mainly used for
precision work on a tools, dies,
gauges, and in machining work
where accuracy is needed.
 This lathe machine is costlier
than an engine lathe of the same
size.

• A lathe in which the work piece is automatically fed
and removed without use of an operator. It requires
very less attention after the setup has been made
and the machine loaded.

 Once tools are set and the machine is started
it performs automatically all the operations to
finish the job.
 After the job is complete, the machine will
continue to repeat the cycles producing identical
parts.
 An operator can maintain five or six such a types of
lathes at a time simply look after the general
maintenance of the machine and cutting tools.

• Turret lathe is the adaptation of the engine lathe where the
tail stock is replaced by a turret slide(cylindrical or
hexagonal). Tool post of the engine lathe is replaced by a
square cross slide which can hold four tools.

 It has heavier construction and provides wider range of
speeds.
 The saddle carrying the turret head moves along the
whole length of the bed. Much longer jobs can be
machined.
 Turret head directly mounted on the saddle. The front
tool post can carry 4 tools and rear tool post may have 1
or 2 tools. Turret may have4 to 6 tools.
 More than one tool may be set to operate
simultaneously. There is no lead screw.

 A highly automated lathe, where both cutting, loading, tool
changing, and part unloading are automatically controlled by
computer coding.
 E.g. CNC Lathe M/C.(Computer Numerical Control Machine)

• This is heavy rugged casting
made to support the working
parts of lathe and also guide
and align major parts of
lathe.
• Made to support working
parts of lathe.
• On top section are machined
ways.
• Guide and align major parts
of lathe.

• The headstock houses
the main spindle, speed
change mechanism, and
change gears.
• The headstock is
required to be made as
robust as possible due to
the cutting forces
involved, which can
distort a lightly built
housing.

• Induce harmonic
vibrations that will
transfer through the
work piece, reducing the
quality of the finished
work piece.

Lathe operations
• All operations performed on a lathe can
divided into two groups.
• Standard or common operations
• Special or rare operation

Standard or common operations
• Plain and step turning
• Eccentric turning
• Facing
• Drilling
• Reaming
• Boring
• Knurling
• Threading
• Chamfering
• forming

Special or Rare operation
• Grinding
• Milling
• Spherical and elliptical turning
• Spinning
• Tapping

Plain and step turning
• Both these operations are simple operation and
can be done by holding the job in many
different ways. The common methods of
holding the work are:
• Between centre
• On a face plate
• In chucks
• On mandrel

Work holding devices
• Chucks
• Collet
• Face
plate

Turning operation
• Tuning operation performed on lathe machine
• Job (work piece) – rotary motion
• Tool – linear motions

Operating/Cutting
Conditions
1. Cutting Speed (v)
2. Feed (f)
3. Depth of Cut (d)

Turning operation
• Turning –a machining process in which a
single-point tool remove material from the
surface of a rotating work piece. (Lathe).
• Rotational speed:
• Depth of cut

Turning operation
• Feed rate
• Timining of machining:
• Material Removal Rate:

Difference between shaper and planer
Shaper planer
In a shaper machine work is held stationary
and the cutting tool on the ram is moved back
and forth across the work
In a planar machine, the tool is stationary and
work piece travels back and forth under the
tool.
Shaper can be used for shaping much smaller
jobs
A planer is meant for larger jobs than can be
undertaken on a shaper. Jobs as large as 6
meter wide and twice as long can be machined
on a planer.
A shaper is a light machine A planer is a heavy duty machine
Shaper can employ light cuts and finer feed Planer can employ heavier cuts and coarse
feed
Shaper uses one cutting tool at a time. Planer uses several tools to cut simultaneously.
The shaper is driven using quick return
mechanism
The drive on the planer table is either
by gears or by hydraulic means.
It is less rigid and less robust. Due to better rigidity of planer machine,
compared to that of a shaper, planer can give
more accuracy on machined surfaces

Shaping, Planing and Slotting
Operations
• Shaping, planning and slotting can be defined as
the process of removing metal from a surface in
horizontal, vertical and inclined position to
produce a flat or plane surface, slots and grooves
by means of a relative reciprocating motion
between the tool and workpiece.
• The difference between the three processes of
shaping, planing and slotting is that in shaping
and slotting, the tool is reciprocating and the
workpiece is fed in to the cutting tool while in
planning, the workpiece is reciprocating and the
tool is fed in.

• The tool reciprocates horizontally in the
shaping and vertically in slotting.
• The cutting is intermittent in all the three
processes because in the relative reciprocating
motion the tool cuts only in forward
working(or cutting)stroke followed by the idle-
return stroke.

The Shaper
• The machine tool used for shaping operation is
called shaper.
• It is designed for machining flat surfaces on small
sized jobs. If the size of the job is large, then
planing is used.
• In a shaper, the work piece is held stationary
during cutting, while the tool reciprocates
horizontally. The feed and depth of cut are
normally provided by moving the work. Such
shaper is called a horizontal shaper.

Types of Shaping Machines
• Shaping machines are the reciprocating type
of machine tools in which the work piece is
held stationary and the tool reciprocates.
• Most shapers have reciprocating motion in
horizontal position(horizontal shapers) but
shapers are also designed with reciprocating
motion in vertical position (vertical shapers)
or slotting machines or slotters.

Metal forging
Hot working Cold working
: Metal is fed to the rolls after being
heated above the recrytallization
temperature
1: Metal is fed to the rolls when it is below
the recrystallization temperature
Co-efficient of friction between two rolls
and the stock is higher, it may even
caused shearing of the metal in contact
with rolls
Co-efficient of friction between two rolls
and the stock is comparatively lower.
Experiment measurement are difficult to
make.
Experiment measurement can be carried
out easily in cold rolling.
Heavy reduction in area of the work piece
can be obtained
Heavy reduction is not possible.
Mechanical properties are improved by
breaking cast structure are refining grain
sizes below holes and others, similar
deformation in ingot (get welded) and or
removed the strength and the toughness
of the job should increases
Hotness increased excessive cold working
greatness crackers ductility of metal
reduction. Cold rolling increased the
tensile strength and yield strength of the
steel.

Rolls radius is generally larger in siz. Rolls radius is smaller
Hot roll surface has(metal oxide) on it ,
this surface finish is not good
The cold rolled surface is smooth and
oxide free
Hot rolling is used un ferrous as well as
non ferrous metals such as industries for
steel , aluminum, copper , brass, bronze ,
alloy to change ingot into slabs
Cold rolling is equally applicable to
both plain and alloys steels and non
ferrous metals and their alloys

Types of Forging Processes
• Impression die forging
• Cold forging
• Open die forging
• Seam less rolled ring forging

Impression Die Forging
• Impression-die forging, occasionally called closed-die
forging, is performed with dies that have the inverse of the
desired shape of the part.
• The process is illustrated by three-step sequence in Figure .
• The raw work piece is shown as a cylindrical element
similar to that used in open-die forging operation. As the
die closes to its last position, flash is shaped by metal that
flows beyond the die cavity and into the little gap between
the die plates. Although this flash should be cut away from
the part in a subsequent trimming operation, it actually
serves an significant function during impression-die forging
operation

Fig.1 Sequence in impression-die forging: (1) just prior to initial contact with raw
work piece, (2) partial compression, and (3) final die closure, causing flash to form in
gap between die plates.

Cold forging
• Cold forging is generally done at room temperature or at a
temperature where there is no changes in the micro structure of
the metal. It's a compressive process where metal workpieces are
plastically shaped by contoured dies by squeezing it between the
dies.
• The process starts with a chemically lubricated bar slug forced
inside a closed die under very high pressures. The metal then flows
and takes the desired shape.
• The Material used can be lower end alloys and carbon steels to 300
and 400 series stainless steel, selected aluminum alloys, bronze and
brass.
• There is a constant quest to optimize the production processes and
decrease the costs. In this direction techniques like numerical
analysis and simulations are now increasingly used.

Cold Forging Methods
• Cold forging can be done by the following
three processes
• Forward Extrusion
• Backward Extrusion
• Upsetting or Heading

Forward Extrusion
• In this process the metal flows in the direction
of the ram force. It reduces the slug diameter
by increasing its length. Typically used to
produce stepped cylinders and shafts.

Backward Extrusion
• Here the metal flow is opposite to the ram
force. It generates hollow parts. Typical
Application for mass production

Upsetting or Heading
• In this process the metal flows perpendicularly
to the ram force thereby increasing the
diameter and reducing the length.
• Typically employed for making fasteners

Application of the Cold Forging
Process
• Cold forgings are very popular with the
automobile industry for manufacturing
steering and suspension parts, anti lock-
braking systems, axles, bits, clutch hubs, gears,
pinions, pins, step and intermediate shafts
and sleeves.

Open die forging
• Forging is the process of shaping metal through the application of force.
• Open-die forging is also known smith forging. In open-die forging, a
hammer strikes and deforms the workpiece, which is placed on a
stationary anvil.
• Open-die forging gets its name from the fact that the dies (the surfaces
that are in contact with the workpiece) do not enclose the workpiece,
allowing it to flow except where contacted by the dies. Therefore the
operator needs to orient and position the workpiece to get the desired
shape.
• The dies are usually flat in shape, but some have a specially shaped
surface for specialized operations.
• For example, a die may have a round, concave, or convex surface or be a
tool to form holes or be a cut-off tool. It is different from closed die
forging in that the workpiece is not enclosed by the dies and the dies
themselves are more like tools with simple shapes and profiles rather than
resembling enclosed molds.

Open die forging
• The process of open die forging serves many
purposes, besides simply shaping the metal.
• Forging of the metal aligns and refines the grain
of the metal, which increases strength as well as
reducing porosity, which is the presence of any
air bubbles, even those too small to be seen with
the naked eye.
• It also improves the ability of the metal to
respond to machining. Forged metal parts have
improved wear resistance and other mechanical
properties over similar machined or cast parts.

Advantages of Open-Die Forging
• Reduced chance of voids
• Better fatigue resistance
• Improved microstructure
• Continuous grain flow
• Finer grain size
• Greater strength

Seam less rolled ring forging
• 1. The ring rolling process typically begins with
upsetting of the starting stock on flat dies at
its plastic deformation temperature - in the
case of grade 1020 steel, approximately 2200
degrees Fahrenheit

• 2. Piercing involves forcing a punch into the
hot upset stock causing metal to be displaced
radially, as shown by the illustration.

• 3. A subsequent operation, shearing, serves to
remove the small punchout ...

• 4. ...producing a completed hole through the
stock, which is now ready for the ring rolling
operation itself. At this point the stock is called
a preform.

• 5. The doughnut-shaped preform is slipped
over the ID roll shown here from an "above"
view

• 6. A side view of the ring mill and preform
workpiece, which squeezes it against the OD
roll which imparts rotary action.

• 7. ...resulting in a thinning of the section and
correspondence increase in the diameter of
the ring. Once off the ring mill, the ring is then
ready for secondary operations such as close
tolerance sizing, parting, heat treatment and
test/inspection

Rolling of Metals: Process and
Principles
• The process of shaping metals into semi-finished or
finished forms by passing between rollers is called
rolling.
• Rolling is the most widely used metal forming process.
It is employed to convert metal ingots to simple stock
members like slabs, sheets, plates, strips etc.
• In rolling, the metal is plastically deformed by passing it
between rollers rotating in opposite direction.
• The main objective of rolling is to decrease the
thickness of the metal. Ordinarily, there is negligible
increase in width, so that the decrease in thickness
results in an increase in length.

• Rolling is done both hot and cold. It is accomplishes in
rolling mills. A rolling mill is a complex machine having two
or more working rollers, supporting rollers, roll stands,
drive motor, reducing gear, flywheel, coupling gear etc.
• Rollers may be plain or grooved depends upon the shape of
rolled product. The metal changes its shape gradually
during the period in which it is in contact with the two
rollers.
• The range of products that can be produced by rolling is
very large. Rolling is a more economical method of
deformation than forging when metal is required in long
lengths of uniform cross-section.

• It is one of the most widely used among all
the metal working processes, because of its
higher productivity and lower cost. The
materials commonly rolled are steel, copper,
magnesium, aluminum and their alloys.

Process of Rolling
• Rolling process has three steps to complete
the product
• (i) Primary Rolling
• (ii) Hot Rolling
• (iii) Cold Rolling

Primary Rolling
• Primary rolling is used to convert metal ingot
to simple stock members like blooms and
slabs. This process refines the structure of
casted ingot, improves its mechanical
properties, and eliminates the hidden internal
defects.

(ii) Hot Rolling
• Blooms and slabs obtained from primary
rolling, again converted into plates, sheets,
rods and structural shapes, by hot rolling
process

(iii) Cold Rolling
• Cold rolling is usually a finishing process in
which products made by hot rolling are given
a final shape. These processes provide good
surface finish, closer dimensional tolerances
and enhance mechanical strength of the
material.

Sequence of operation in rolling a bar

Principles of Rolling
• The rolling is a process which consists of passing the metal through
a gap between rollers rotating in opposite direction. This gap is
smaller than the thickness of the part being worked. Therefore, the
rollers compress the metal while simultaneously shifting it forward
because of the friction at the roller-metal interfaces.
• When the work piece completely passes through the gap between
the rollers, it is considered fully worked. As a result, the thickness of
the work is decreases while its length and width increases.
• However, the increase in width is insignificant and is usually
neglected. The Fig. 2.4 shows the simple rolling operation of a
plate. The decrease in thickness is called draft, whereas the
increase in length is termed as absolute elongation. The increase in
width is known as absolute spread.

coefficient of elongation can be given
as follows

Defects in Rolled Products
• A number of defects in the rolled products
arise during rolling process. A particular defect
is usually arrived with a particular process and
does not arise in other processes
• Some of the common defects in rolled
products are given below

(i) Edge Cracking
• Edge cracking generally occurs in rolled ingots,
slabs, or plates. This is due to, either limited
ductility of the work metal or uneven
deformation, especially at the edges

(ii) Folds
• Folds are a defect generally occurs in plate
rolling. This is caused if the reduction per pass
is too small.

(iii) Alligatoring
• Alligatoring is the defect, usually occurs in the
rolling of slabs (particularly aluminum and
alloys). In this defect, the work piece splits
along a horizontal plane on exit, with the top
and bottom. This defect always occurs when
the ratio of slab thickness to the length of
contact fall within the range of 1.4 to 1.65. Fig.
2.15. Shows the defect of Alligatoring.

(iv) Scale Formation
• When the metal is hot rolled, its surface is not
smooth and it has scale (oxide) formed over it.

Types Rolling mills
• Rolling mills consists of bearings to supports the
gear box, motor, speed control devices, hydraulic
system and rolls etc. Rolling mills are dividing in
to several types they are
• Two high rolling mills,
• Three high rolling mills,
• Four high rolling mills,
• Tandem rolling mills and
• Cluster rolling mills

Two High rolling mills
• In the two high rolling mills two reversed rolls
are used for the process. One roll is operated
in one direction and the other is operated in
the opposite direction. The two high rolling
mills are divided in to two types they are
• Reversing mills
• non-reversing mills

Two High Reversing Mills
• The two high reversing type mills type are
used in the slabing mills and measuring and
for outline work in rails, mills, plates, and
structure. Compare with the other process
this is very expensive.by using this type of
mills we can increase the productivity of the
material.

Two high non reversing mills
• In the two high non reversing mills are
operating in the same direction. Both the rolls
are moving in the same direction
continuously. In this process less amount of
motive force is used .the material must be
carried back every time and passing the
material in to the rolls. This process is used in
the train plate mills

Three high rolling mills
• In this process we can see three rolls they are arranged in the
parallel direction one above the other. The roll is travelling in
the opposite direction at that time of process the material
may be moving in between the top and middle roll in one
direction and the middle and foot roll in the opposite
direction. Initially the work piece must be passed through the
foot roll and then middle roll then it returns in between the
middle and the first rolls. During the passes in between the
rolls the thickness of the work piece material must be
reduced. Lifted tables are arranged on the tables to move the
material in vertical direction or either sides. Because of that
arrangement the material must be suckled automatically into
the gaps present in the rolls.by using three high rolling mills
we can produce groove and plain surface on the work piece
material.

Four high rolling mills
• In this milling process four rolls are arranged one
above the other. The upper and lower rolls are
operating in one direction and the middle two
rolls are operating in opposite direction. Compare
with the upper and lower rolls the middle two
rolls are smaller in size. The upper and lower rolls
are known as backup rolls they are providing
hardness to the work rolls (middle rolls).the four
rolling are used for the rolling of the plates,
sheets and strips for cold and hot rolling

Cluster rolling mills
• Cluster rolling mill is special type of four high
rolling. In this type of rolling mills two back up
rolls are arranged to the work rolls. This type
of rolling mills is suitable for the very small
diameter materials with suitable lengths

Difference between hot and cold
Extruction
• Hot extrusion is a hot working process, which means it
is done above the material’s recrystallization
temperature to keep the material from work hardening
and to make it easier to push the material through the
die.
• Most hot extrusions are done on horizontal hydraulic
presses that range from 230 to 11,000 metric tons .
Pressures range from 30 to 700 MPa , therefore
lubrication is required, which can be oil or graphite for
lower temperature extrusions, or glass powder for
higher temperature extrusions.

Hot Extruction
• The biggest disadvantage of this process is its cost
for machinery and its upkeep
• The extrusion process is generally economical
when producing between several kilograms and
many tons, depending on the material being
extruded.
• There is a crossover point where roll forming
becomes more economical. For instance, some
steels become more economical to roll if
producing more than 20,000 kg

Cold Extruction
• Cold extrusion is done at room temperature or
near room temperature. The advantages of this
over hot extrusion are the lack of oxidation,
higher strength due to cold working, closer
tolerances, better surface finish, and fast
extrusion speeds if the material is subject to hot
shortness.
• Materials that are commonly cold extruded
include: lead, tin, aluminum, copper, zirconium,
titanium, molybdenum, beryllium, vanadium,
niobium, and steel.

Wire and bar drawing - Basic concepts:
• Bar or wire drawing is a deformation process
in which the work piece in the form of
cylindrical bar or rod is pulled through a
converging die.
• The stress applied is tensile. However, the
material is subjected to compressive stress
within the die thereby deforming plastically.

• A wire is a circular, small diameter flexible rod. Wire
drawing is an cold working process. It is an operation
to produce wire of various sizes within certain specific
tolerances.
• This process involves reducing diameter of thick wire
by passing it through a series of wire drawing dies with
successive die having smaller diameter than the
preceding one.
• Mostly die are made by chilled cast iron, tungsten
carbide, diamond or other tool material. The maximum
reduction in area of wire is less than 45% in one pass.

Rod Drawing
• Rod drawing is similar process like wire drawing
except it is rigid and has larger diameter compare
to wire.
• This process need heavier equipment compare to
wire drawing because the wire can be coiled but
a rod should be kept straight.
• The work piece is first fed into die and pulled by
a carriage which increase its length and decrease
its cross section. Now the rod is to be cut into
sections

Tube Drawing
• Tube drawing is also similar to other two
processes except it uses a mandrel to reduce
wall thickness and cross section diameter of a
tube.
• This mandrel placed with die and the work
piece is pulled by a carriage system as
describe in rod drawing. The tube is either
circular or rectangular. It also required more
than one pass to complete drawing operation

Working Process
• All drawing process works on same principle. Its
working can be summarized as follow
• First a hot rolled rod is created by other metal
forming processes like forging,
extruding, centrifugal casting etc.
• Now the rod is made pointed to facilitate the
entry into the die.
• The dust or other scale particle should clean from
the rod. This process is done by acid pickling.

• Now the prepared skin is coated with lubricant. This
process uses either sulling, coppering, phosphating or
liming process. Sulling is a process of coating with
ferrous hydroxide. In phosphating magnesium or iron
phosphate is coated. Cu and Sn are used for lubricant
high strength material. Oil and grease use for wire
drawing and soap is used for dry drawing.
• Now the rod is pulled through various dies to convert it
into desire shape. The die is affected by
several stresses so it is made by high strength alloy
steel like tungsten carbide etc

Application
• This process is used for making wire of copper,
aluminum etc. which are used in electrical
industries.
• Paper clip, helical spring etc. are wire drawing
product.
• Small diameter rods and tubes are drawing
product.
• It is used to produce large length of small
cross section.

Moulding
• Plastics
• There are two main types of plastics
• Thermoplastics
• Thermosets

Thermoplastics
• Thermoplastics which are softened by heat
and can be moulded. (Injection moulded,
blow moulded or vacuum formed). Good
examples are acrylic, polypropylene,
polystyrene, polythene and PVC

Thermosets
• Thermosets which are formed by ha heat process
but are then set (like concrete) and cannot
change shape by reheating. Good examples are
melamine (kitchen worktops), Bakelite (black
saucepan handles), polyester and epoxy resins.
• Composites are made by mixing materials
together to get enhanced properties. Polyester
resin is mixed with glass fibre to make GRP used
for boatbuilding and fishing rods. Epoxy resin plus
carbon fibre is stronger than steel but lighter

Nylon
• Very strong, nylon can be machined and will take a fine
thread. It is also slippery and can be used to make washers,
spacers and bushes.
• Nylon was originally developed as a textile but is available
in many forms with vastly different properties. Engineering
nylon grades are easy to machine with good resistance to
biological attack. Unfortunately nylons can absorb moisture
from the atmosphere and can degrade in strong sunlight
(they are unstable in ultraviolet light) unless a stabilising
chemical is added at the initial manufacture of the plastic.
Nylons are easy to mould. Nylons also have a natural 'oily'
surface that can act as a natural lubricant. Nylons are used
for everything from clothes through to gears and bearings.

Acrylic
• Comes in a range of thicknesses, colours and can be
opaque or transparent. There are two type of acrylic
extruded which is cheaper and very "plastic" and cast
which machines better but is harder and less flexible.
• Acrylics are available in a range of colours and can be
opaque, translucent or transparent. They are available in
sheet, rod, and tube for use in injection moulding, extrusion
and vacuum forming. Acrylics withstand weather and are
stable in sunlight. Almost any colour can be produced.
Transparent acrylic can be as clear as the finest optical
glass, this led them to be used in optical equipment such as
cameras. It is possible to significantly strengthen the acrylic
when it is being made, these high grade acrylics are used
use for aircraft windows

PVC and uPVC
• Stiff, hard,tough lightweight plastic. uPVC is
stabilised for outside use ans is uded for
plastic windows and plastic pipes. Plasticised
PVC is used for flexible applications such as
insulating - cables

Polythene
• This plastic has a range of uses from food
packaging to gas pipes. The plastics can be
injection moulded or extruded and is available
in two forms. High-density polyethylene
(HDPE) is a hard rigid plastic. A low-density
grade ( LDPE )is tough and flexible.

Polypropylene
• Polypropylene is a tough, cheap plastic, it has
a slightly waxy feel. It can be bent repeatedly
without breaking. Used for Medical
equipment such as syringes, stacking chairs
(chairshell is polypropylene), suitcases with
integral hinges,

Polycarbonate
• Used for making eye protection, machine
guards and riot shields. It is not as hard as
acrylic and can be cut easily but it will absorb
impacts

Bakelite
• A thermosetting plastic. Dark brown. Used as
a composite reinforced with paper or cloth.
Used to make circuit boards and heat proof
insulated parts in the electronics industry.

Epoxy resin
• A two part mix which can be used as a glue
(ARALDITE) or be reinforced with carbon fibre
to produce a very strong and light composite
materials which is used in aerospace and
Formula 1

Melamine
• A thermoset very tough and heat resistant.
White but can be produced in a full range of
colours

The History of Plastic Moulding
• Plastic moulding began in the late 1800’s to fill the
need for plastic billiard balls as opposed to the
commonly used ivory billiard balls of the time.
• In 1868, John Wesley Hyatt invented a way to make
billiard balls by injecting celluloid into a mould.
• Four years later, Hyatt and his brother invented and
patented a machine to automate the process.
• This was the first plastic injection moulding machine in
existence and it used a basic plunger to inject plastic
into a mould through a heated cylinder

• In 1946, the screw injection
moulding machine was invented
by James Hendry, which replaced
the plunger injection technique.
This is the technique most
commonly used today
• Modern rotational moulding also
has a rich history beginning in
1855 when rotation and heat
were used to produce metal
artillery shells in Britain.

• Plastics were introduced into the process in
the early 1950’s, when rotational molding was
first used to manufacture doll heads. And then
in the 1960’s the modern process of rotational
molding that allows us to create large hallow
containers with low-density polyethylene was
developed

Types of moulding
• The most popular techniques in plastic
molding are rotational molding, injection
molding, blow molding, compression molding,
extrusion molding, and thermoforming

Rotational Moulding
• Rotational Moulding, also called roto moulding, is a
manufacturing process for producing large hollow parts
and products by placing a powder or liquid resin into a
metal mould and rotating it in an oven until the resin
coats the inside of the mould.
• The constant rotation of the mould creates centrifugal
force forming even-walled products. Once the mould
cools, the hardened plastic is removed from the mould.
• Very little material is wasted during the process, and
excess material is often re-used, making it economical
and environmentally friendly

Common Uses for Rotational
Moulding
• Rotational moulding is commonly used to
make large hollow plastic products like utility
carts, storage tanks, car parts, marine buoys,
pet houses, recycling bins, road cones, kayak
hulls, and playground slides

Rotational Moulds Are Highly
Customizable And Cost Effective
• The mould itself can be highly intricate to
facilitate the moulding of a wide range of
products. Moulds can include inserts, curves and
contours as well as logos and slots for plastic or
metal inserts to be placed after a product is
moulded
• Tooling costs are lower with rotational moulds
than injection or blow moulds. The results are
lower start-up costs and cost-effective production
runs even when producing as few as 25 items at a
time.

Injection Moulding
• Injection moulding is the process of making
custom plastic parts by injecting molten
plastic material at high pressure into a metal
mould. Just like other forms of plastic
moulding, after the molten plastic is injected
into the mould, the mould is cooled and
opened to reveal a solid plastic part.
• The process is similar to a Jello mould which is
filled then cooled to create the final product.

Common Uses for Injection Molding
• Injection moulding is commonly used for making very high
volume custom plastic parts. Large injection moulding
machines can mould car parts.
• Smaller machines can produce very precise plastic parts for
surgical applications.
• In addition, there are many types of plastic resins and
additives that can be used in the injection moulding
process, increasing its flexibility for designers and
engineers.
• Injection moulds, which are usually made from steel or
aluminum, carry a hefty cost. However, the cost per part is
very economical if you need several thousand parts per
year

Blow Molding
• Blow moulding is a method of making hollow, thin-
walled, custom plastic parts. It is primarily used for
making products with a uniform wall thickness and
where the shape is important. The process is based
upon the same principle as glass blowing
• Blow moulding machines heat up plastic and inject air
blowing up the hot plastic like a balloon. The plastic is
blown into a mould and as it expands, it presses
against the walls of the mould taking its shape. After
the plastic “balloon” fills the mould, it is cooled and
hardened, and the part is ejected. The whole process
takes less than two minutes so an average 12 hour day
can produce around 1440 pieces

Common Uses for Blow Molding
• Blow moulding processes generate, in most
cases, bottles, plastic drums, and fuel tanks. If
you need a hundred thousand plastic bottles,
this is the process for you.
• Blow moulding is fast and economical with the
mould itself costing less than an injection
moulding, but more than rotational
moulding[8] … sometimes as high as 6 to 7
times as much as a roto-molding tool

Compression Molding
• Compression molding is work on compresstion. A
heated plastic material is placed into a heated
mold and then pressed into a specific shape.
Usually, the plastic comes in sheets, but can also
be in bulk. Once the plastic is compressed into
the right shape, the heating process ensures that
the plastic retains maximum strength. The final
steps in this process involve cooling, trimming,
and then removing the plastic part from the
mold.

Production engineering

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