Mechanism of machining, Types, Tools, Me

COURSE OUTLINE
MANUFACTURING TECHNOLOGY 2
Lesson 1.
Mechanics of
Metal Cutting
1
Lesson 2.
Turning
Machines
2
Lesson 3.
Reciprocating
Machine Tools
3
Lesson 4.
CNC Machines
4
Lesson 5.
Programming
of CNC
Machine Tools
5

FIRST LESSON
We will cover these Knowledge:
 Manufacturing Process
 Classification of Manufacturing
Process
 Basic Mechanics of Metal
cutting
 Factors Affecting Machinability
3

FIRST LESSON
SUMMARY
 It’s important for UG
Mechatronics students to
understand the
Manufacturing Process and
its types.
 Understand the mechanics
of chip formation and types
of chip formation.
 Describe about cutting
tools, types and cutting
tools materials.
 Describe about Tool life,
Tool wear, Surface finish,
Cutting fluid and
Machinability.

5
MANUFACTURING TECHNOLOGY
COURSE PROGRESS
Session 1. Manufacturing
Session 2. Mechanics of Chip Formation and Chip types
Session 3. Cutting tool and its Types
Session 4. Nomenclature of single point cutting tool
Session 5. Types of Cutting
Session 6. Cutting tool materials and properties
Session 7. Types of tool failure, Tool wear and Tool life
Session 8. Simple tool life calculations
Session 9. Surface finish, Cutting Fluids, Machinability

6
MANUFACTURING
 ‘Manufacturing’ is derived from the Latin, manus = hand and
factus = made, that is, the literal meaning is “made by hand”.
 ‘Manufacturing’ means the making of goods and articles by
hand and/or by machinery.
 ‘Manufacturing Technology’ or “Production Technology” can be
defined as the study of the various processes required to
produce parts and to assemble them into machines and
mechanisms.

7
MANUFACTURING PROCESS
 Production of Goods in large quantities by using machines.

8
TYPES

9
MATERIALS REMOVAL PROCESS
 Material removal process is a type of manufacturing process in
which the final product is obtained by removing excess metal
from the stock.
 Machining is a general term used to describe material removal
process.

10
MACHINING
• Feed : The distance at which the tool
travels during its single spindle revolution.
• Speed: Cutting speed is considered the
speed of a tool that cuts the work piece.
• Depth of Cut: The depth of cut is the
distance that the tool bit moves into the
work.

11
MATERIAL REMOVAL PROCESS TYPES

12
CONVENTIONAL MACHINING PROCESS
 Material removed from the surface of the work piece by
means of sharp cutting tools.
 Examples : Turning, Milling, Drilling, etc…

13
ABRASIVE MACHINING PROCESS
means of hard abrasive particles.
 Examples : Grinding

14
UNCONVENTIONAL MACHINING PROCESS
means of various form of energy other than sharp cutting
tools.
 Examples : EDM, WJM, AJM, etc…

15
SESSION OUTCOME
Understand what is manufacturing.
Understand types of manufacturing
process.
Understand the Material removal
process.
At the end of the session students able to

16
MECHANISM OF MATERIAL REMOVAL
 Relative motion between the
cutting tool and the work piece
develops a cutting action.
 Cutting action involves shear
deformation of work material to
form a chip.
 The cutting itself is a process of
extensive plastic deformation to
form a chip that is removed
afterward and new surface
exposed.

17
Generating shape :
Relative motion between
tool and work piece.

18
Forming to create
shape: Shape of the
cutting tool.

19
MACHINING OPERATIONS
 Turning
 Drilling
 Milling
 Shaping &
Planing
 Broaching
 Sawing

20
TURNING OPERATIONS
Turning : Single point cutting tool removes material from a
rotating work piece to form a cylindrical shape

21
DRILLING OPERATIONS
Drilling : Used to create a round hole, usually by means of
a rotating tool (drill bit) with two cutting edges

22
MILLING OPERATIONS
Milling : Rotating multiple-cutting-edge tool is moved
across work to cut a plane or straight surface
 Two forms: peripheral milling and face milling

23
CHIP FORMATION
 The cutting tool produces
internal shearing action in the
metal.
 The metal below the cutting
edge yields and flows
plastically in the form of chip.
 When the ultimate stress of
the metal is exceeded,
separation of metal takes
place.

24
TYPES OF CHIP FORMATION
 Continuous
 Built-up edge
 Serrated or
segmented
 Discontinuous

25
Continuous Chip
• Continuous chips have a continuous
segment.
• This chip is form during cutting of
ductile material like aluminum, mild
steal, cooper etc. with a high cutting
speed.
• The friction between tool and material
is minimum during this process
• Continuous chip formation results in
less heat generation, reduced tool
wear, and improved surface finish
compared to other metal cutting

26
FACTORS
 A ductile metal such as mild steel is to be used.
 The large rake angle of the tool.
 High cutting speed.
 Minimal friction between the chip and tool interface.
 Small depth of cut.

27
ADVANTAGES
 The surface finishes better.
 Less heat generates.
 Long tool life.
 Less friction.
 Low power consumption.

28
DISADVANTAGES
 It is difficult to handle.
 Difficult to dispose

29
Discontinuous Chip
• The chips formed during machining
process is not continuous i.e. formed
with breakage is called discontinuous
chips.
• Discontinuous types of chips are
formed when hard and brittle metals
like brass, bronze and cast iron is
machined.

30
FACTORS
 Low feed rate.
 Small rake angle of the tool.
 High cutting speed.
 High friction forces at the chip tool interface.
 Too much depth of cut.

31
ADVANTAGES
 The formation of discontinuous types of chips in brittle
materials provides good surface finish, increases the tool
life and reduces the consumption of power.

32
DISADVANTAGES
 When discontinuous chips are formed in the ductile materials, the work piece
result in poor surface finish and excessive wear and tear of the tool takes
place.

33
CONTINUOUS CHIP WITH BUILT UP EDGE
• When the chip is flows in upward direction and high friction is exist in
between the interface of the chip and tool.
• Due to the high friction between the chip and tool a very intense heat is
generated at the nose of the tool.
• The compressed metal adjacent to the tool nose gets welded to it.
• This compressed metal welded to the nose is called built up edge.

34
CONTINUOUS CHIP WITH BUILT UP EDGE
When the chip flows through this built up edge, it gets broken and carried
away by the chip and called as built up edge chips, the rest of the built up
edge is adhere to the surface of the work piece and makes it rough.

35
FACTORS
 Excessive feed rate.
 The small rake angle of the tool.
 Low cutting speed.
 Lack of coolant and this increase the friction between the chip tool interfaces.

36
ADVANTAGES
 The making of the BUE has one advantage i.e. it protects the tool from
getting damaged from high friction and temperature generated during
the machining process and hence the tool life increases.

37
DISADVANTAGES
 The formation of these types of chips results in rough surface finish, change
in the rake angle and cutting forces.

38
SERRATED CHIP OR SEGMENT CHIP
This type of chip formation occurs while machining the difficult-to-machine
materials (such as titanium alloys, nickel-based super alloys, and austenitic
stainless steel) at high cutting velocities.

39
FACTORS
 Using difficult-to-machine materials (such as titanium alloys, austenitic
stainless steels etc…)
 High cutting velocities.

40
COMPARISION

41
CONDITIONS

42
SESSION OUTCOME
Understand the Mechanism of Material removal
Understand types of Machining operation.
Understand the types of chip formation and its
factors.

43
CUTTING TOOLS
Cutting tools is a wedge-shaped and
sharp-edged tools used to remove
excess layers of material from a work
piece by shearing during machining to
obtain the desired shape, size, and
accuracy.

44
TYPES OF CUTTING TOOL
Single Point Cutting Tool
Multipoint Cutting Tool

45
SINGLE POINT CUTTING TOOL
Single points cutting tool has only one
main cutting edge that can remove
material at once in a single pass. Single
point cutting tool is used in turning,
shaping, planning, and similar operations.

46
MULTIPOINT CUTTING TOOL
A multi-point cutting tool contains more
than two main cutting edges that
simultaneously engage in cutting action
in a pass.

47
CLASSIFICATION

48
COMPARISON

49
SESSION OUTCOME
Understand the classification of cutting tools
Differentiate single and multi point cutting tools.

50
SINGLE POINT CUTTING TOOL NOMENCLATURE

51
TERMINOLOGY
Shank:
The main body of the tool is known
as the shank. It is the backward part
of the tool which is held by tool
post.
Face:
The top surface tool on which chips
passes after cutting is known as a
face. It is the horizontal surface
adjacent of cutting edges.
Flank:
Sometime flank is also known as
cutting face. It is the vertical surface

52
TERMINOLOGY
Flank:
Sometime flank is also known as
cutting face. It is the vertical surface
adjacent to the cutting edge.
According to cutting edge, there are
two flank side flank and end flank.
Nose or Cutting Point:
The point where both cutting edge
meets known as cutting point or
nose. It is in front of the tool.

53
TERMINOLOGY - ANGLES
End Cutting Edge Angle:
The angle between the end cutting
edge or flank to the plane
perpendicular to the side of the
shank is known as the end cutting
angle.
This angle usually varies from 5 to
15 degree
Side Cutting Edge Angle:
The angle between the side cutting
edge or flank to the plane parallel to
the side of the shank known as side
cutting edge angle.

54
Back Rack Angle:
The angle form to smooth flowing of
chips from the face, known as rack
angle. It allows to smooth flow of
chips.
The back rack angle is the angle
between the face and the plane
perpendicular to the end cutting
edge.
Softer the material, greater should be
the positive rake angle. The back rake
angle may be positive negative or

55
Side Rack Angle:
The angle between the face and plane
perpendicular to the side cutting edge
is known as the side rack angle. It
allows chips to flow smoothly when
material cut by side cutting edge.
The amount by which a chip is bent
depends upon this angle. When the
side rack angle increases, the
magnitude of chip bending decreases.
Smoother surface furnish is produced
by a larger side rake angle.

56
End Relief Angle:
It is also known as a clearance angle.
It is the angle that avoids tool
wear. It avoid the rubbing of flank
with a work piece.
End cutting angle made by end flank
to the plane perpendicular to the
base.
This angle may vary from 6 to 10
degrees.

57
Side Relief Angle:
It is the angle made by the side flank to
the plane perpendicular to the base. It
avoid rubbing of side flank with a work
piece.
This angle allows the tool to fed
sideways into the job in order to cut the
work material without rubbing.
When the side relief angle is very small,
the tool will rub against the job and
therefore it will get overheated and
become blunt and the surface finish
obtained will be poor.

58
SESSION OUTCOME
Understand Single Point Cutting Tool Terminologies.

59
FUNCTIONS AND EFFECTS OF CUTTING TOOL ANGLES
 Back Rack angle:
• It helps to control the chip flow in a convenient direction.
• It reduces the cutting force required to shear the metal and consequently helps
to reduces power requirements and increase tool life.
• It also helps counteract the pressure against the cutting tool from the work by
pulling the tool into the work.
• It provides keenness to the cutting edge and improves the surface finish.

60
 Side Rack angle:
• It performs similar functions as performed by back rake angle.
• Side rake angle along with back rake angle controls the chip flow direction.
• It partly counteracts the resistance of the work to the movement of the cutter.
• For example, brass requires a back and side rake angle of almost 0°, while
aluminum uses a back rake of 35° and a side rake of 15°.

61
 End Relief angle:
• It allows the tool to cut freely without rubbing against the work surface.
• This angle varies from 0° to 15°, and usually 8°.
• Excessive relief angle reduces strength of the tool.

62
 Side Relief angle:
• It avoids the rubbing of flank against the work piece when the tool is fed
longitudinally.
• This angle is 6° to 10° for steel, 8° for aluminum.
• It maintains that no part of the tool besides the actual cutting edge can
touch the work.

63
 End Cutting Edge angle:
• It avoids rubbing between the edge of the tool and workspace.
• It influences the direction of chip flow.
 Side Cutting Edge angle:
• Increase in side cutting edge angle tends to widen and thin the chip.
• An excessive side cutting edge angle redirects feed forces in radial
direction which may cause chatter.

64
 Nose Radius
• A sharp point at the end of tool is undesirable, because it is highly stressed, short lived and
leaves groove in the path of cut. Therefore Nose Radius is favorable for long tool life and good
surface quality.
• It affects the tool life, radial force, and surface quality of work piece.
• If nose radius is too large chatter will occur.
• There is an optimum value of the nose radius at which the tool life is maximum.
• If the nose radius exceeds optimum value, the tool life decreases.
• Larger nose radius means larger area of contact between tool and work piece. Resulting more
frictional heat is generated. Also, cutting force increases due to which the work part may start

65
FACTORS INFLUENCING RAKE ANGLE
 Type of Work piece
material
 Type of Tool Material
 Depth of Cut
 Rigidity of Tool holder
 Condition of machine

66
TOOL SIGNATURE
1. Back rack angle
2. Side rake angle
3. End relief angle
4. Side relief angle
5. End cutting edge
angle
6. Side cutting edge
angle
The tool signature or
tool designation is
used to denote a
standardized system of
specifying the principal
tool angles of a single-
point cutting tool.

67
SESSION OUTCOME
Understand the Functions and Effects of tool angles.
Understand the factors effect the Rake angle.
Understand the standard system Specifying of tool
angles.

68
TYPES OF CUTTING
 Orthogonal Cutting
 Oblique Cutting

69
ORTHOGONAL CUTTING
 Orthogonal cutting, the cutting edge
of the tool is perpendicular to the
direction of motion.

70
OBLIQUE CUTTING
 Oblique cutting-cutting edge travels,
making an angle with the normal of
cutting edge.

72
CUTTING TOOL MATERIALS
 Carbon tool steel.
 High-speed steel tool (HSS)
 Cemented carbide.
 Ceramics tool.
 Cubic boron nitride Tool (CBN)
 Diamond tool.

73
CUTTING TOOL MATERIALS PROPERTIES
 Carbon tool steel.
 High-speed steel tool (HSS)
 Cemented carbide.
 Ceramics tool.
 Cubic boron nitride Tool (CBN)
 Diamond tool.

74
CARBON TOOL STEEL
 These contain small amounts of silicon, chromium, manganese, and vanadium
to refine 0.6–1.5% carbon.
 Properly hardened and tempered.
 This material's wear resistance and hot hardness are very low.

75
HIGH SPEED STEEL (HSS)
 They contain very high concentrations of vanadium, cobalt, molybdenum,
tungsten, and chromium.
 They can be hardened to various depths with proper heat treatment.
 The high toughness and good wear resistance make high-speed steel suitable
for all types of cutting tools of complex size at relatively
moderate cutting speeds.
 The most commonly used tool for taps, drills, reamers, gear tools, end cutters,
slitting, brochures, etc. is using high-speed steel material.

76
CEMENTED CARBIDE
 These are the most important tool materials nowadays due to their high hot
hardness and wear resistance in the hot state.
 These materials are produced from powder metallurgy by sintering tungsten
carbide grains in a cobalt matrix.
 In addition to tungsten carbide, the mixture may contain other carbides such as
titanium carbide (TIC) and or tantalum carbide (Tac).
 The disadvantage of cemented carbides is that have low toughness.

77
CERAMICS
 Ceramics materials are made of fine grain, high purity aluminum
oxide (Al2O3) without pressurizing and sintering.
 White or Cold-Pressed Ceramics- contains 100% Al2O3
 Black or Hot-Pressed Ceramics - contains 70% Al2O3 and 30% Tic.
 Both types of ceramics materials are suitable for continuous operation such as
finish turning of cast iron and steel at very high speeds.

78
DIAMOND
 Diamond is the most hardened material.
 It is used for finishing and cutting very hard materials like mirrors, ceramics, etc.

79
CHARACTERISTICS OF CUTTING TOOL MATERIALS
 Cutting tools should have high strength, hardness even at higher or lower
temperatures.
 It should not change any of the material properties (ductility, hardness,
strength) in the long rung.
 It should have high toughness and should have the ability to withstand shock
and vibration.
 The tool should be cheap in price.
 Easily manufactured.
 It should have a low coefficient of friction.

80
TOOL WEAR
 Wear is a gradual process.
 Tool wear can be defined as the change in
the shape of a tool from its original shape
during the cutting operation, as a result
of the gradual loss of tool material called
tool wear.
 Rate of wear depends upon:
 Work piece material
 Tool material
 Coating
 Tool geometry
 Cutting fluid
 Characteristics of tool

81
TOOL WEAR - DISADVANTAGES
 Tools stop to produce work piece as per required dimensions.
 The tools overheated.
 Excessive surface roughness is observed.
 Tool failure increases the cutting forces and hence the power requirement
will be higher.
 May cause tools breakdown.
 Decreases accuracy of a tool product and tool life.

82
TOOL WEAR MECHANISM
 Wear
 Abrasive wear
 Adhesive wear
 Diffusion wear
 Chemical wear
 Plastic deformation
 Fracture

83
ABRASIVE WEAR
 Related to hardness
 Caused by hard particles in
work piece material
 Caused by particles of the built-
up-edge
 Caused by the transformed
surface (hardened)

84
ADHESIVE WEAR
 Appears at low cutting
temperatures or Cutting
Speeds
 High pressure cause
pressure welds on the top
surface irregularities.

85
DIFFUSION WEAR
 Diffusion is exchange of
chemical elements between tool
and material.
 New compounds or composition
of surface layer is created
(Oxidation, cutting fluid reaction
etc.)

86
PLASTIC DEFORMATION
 All cutting tools, all materials – after some amount of tool wear the contact
surface is too large .
 Massive heat generation leads to rapid temperature increase
 The hardness of material decreases (limiting temperature)
 The high cutting force load leads to loss of geometry and appearance of
plastic deformation(usually together with rapid wear of combined thermo-
mechanical load).

87
FRACTURE
 Cutting force becomes excessive
and/or dynamic, leading to brittle
fracture.
 Premature failure.

88
TYPES OF ABRASIVE WEAR
Flank wear – Occurs flank (Side of
tool)
Crater wear – Occurs top rake face
Principle locations and types of wear
that occur.

89
FLANK WEAR
Flank wear occurs on the relief
face of the tool.
Rubbing of the tool along the
machined surface , cause
abrasive wear.
High temperature affect the
tool material properties.

90
FLANK WEAR
Flank wear will be greater near the nose of the tool, and it is not uniform
along the cutting edge.
It generally results from high temperatures, which affect the tool and
work piece.
This type of wear occurs on all tools when cutting any type of work
material.

91
FLANK WEAR - REASONS
Flank wear increases rapidly with increasing cutting speed and increases in
feed and depth of cut can also result in larger flank wear.
Abrasion by hard panicles in the work piece.
Shearing of micro welds between tool and work piece.
Abrasion by fragments of built-up edge, which strike against the flank face of
the tool.

92
FLANK WEAR - CUTTING TIME
Tool wear is a function of
cutting time.

93
FLANK WEAR - CUTTING SPEED
Tool wear is a function of
cutting Speed.

94
FLANK WEAR - REMEDIES
Reduce cutting speed, feed, and depth of cut.
Use the hard grade of carbide & prevent the formation of built-up breakers.

95
CRATER WEAR
The wear on the rake face of the tool is
called crater wear.
In crater wear, chips erode the rake face of
the tool.
Chips flow across the rake face develop
severe friction between the chip and rake
face.
It does not degrade the use of tools until it
creates cutting-edge failure.

96
CRATER WEAR
Crater wear can increase the working rake angle and reduce the
cutting force, but it will also weaken the strength of the cutting
edge.
This is more common in ductile materials such as steel that
produce continuous chips over long periods of time.
Crater depth is the most commonly used parameter in evaluating
rake face wear.

97
CRATER WEAR - REASONS
Severe abrasion between chip-tool interfaces, especially on the rake face.
High temperature in the tool-chip interface.
Increase in feed results in rising in the temperature of the tool-chip interface.
An increase in cutting speed leads to an increase in chip velocity at the rake
face, thereby increasing the temperature at the chip-tool interface and hence
increasing crater wear.

98
CRATER WEAR - REMEDIES
By using proper coolant for rapid heat dissipation from the tool-
chip interface.
Reduced cutting speeds and feed rates.
Use tougher and hot hardness materials for tools and have a
positive rake angle.

100
NOSE WEAR
Nose wear occurs as a result of abrasion between the nose and
the metal machinability.
It is considered a part of flank wear as there is no specific
boundary between them.
It is also called corner wear.

101
TOOL LIFE
Useful cutting life of tool expressed
in time.
Time period measured from start of
cut of failure of tool,
Time period between two
consecutive resharpening or
replacement

102
TAYLORS EQUATION

103
TOOL LIFE CALCULATION
A single point cutting tool can be used
up to 15 hours at 65 m/min. If the
Taylor’s constant C=300, Calculate the
percentage of reduction in tool life on
double the cutting velocity
In a single point turning operation of steel
with cemented carbide tool, Taylors tool life
exponent is 0.2. Determine the increase in
the tool life if the cutting speed is halved.
A single point cutting tool can be used up
to 20 hours at 55 m/min. If the Taylor’s
constant C=320, Calculate the percentage
of reduction in tool life on double the
cutting velocity.

104
CUTTING FLUIDS
 A cutting fluid is any liquid or gas that is
applied directly to the machining
operation to improve cutting performance.
 Cutting fluids address two main problems:
 Heat generation at the shear zone and
friction zone, and
 Friction at the tool–chip and tool–work
interfaces.

105
FUNCTIONS OF CUTTING FLUIDS
 To prevent the tool from overheating, i.e. so that no temperature is reached where the tool's hardness and
resistance to abrasion are reduced, thus decreasing the tool life.
 To keep the work cool, preventing machining that results in inaccurate final dimensions.
 To reduce power consumption, wear on the tool, and the generation of heat, by affecting the cutting process.
This investigation wishes to establish a relationship between the surface chemistry of the lubricants involved
and how they can accomplish reducing the contact length on the rake face of the tool where most of the heat
during cutting is produced.
 To provide a good surface finish on the work.
 To aid in providing a satisfactory chip formation (related to contact length)
 To wash away the chips/clear the swarf from the cutting area.
 To prevent corrosion of the work, the tool and the machine.

106
PROPERTIES OF CUTTING FLUIDS
 High thermal conductivity for cooling .
 Good lubricating qualities.
 High flash point, should not entail a fire hazard.
 Must not produce a gummy or solid precipitate at ordinary working temperatures.
 Be stable against oxidation.
 Must not promote corrosion or discoloration of the work material.
 Must afford some corrosion protection to newly formed surfaces.
 The components of the lubricant must not become rancid easily.
 No unpleasant odor must develop from continued use.
 Must not cause skin irritation or contamination.
 A viscosity that will permit free flow from the work and dripping from the chips.

107
TYPES OF CUTTING FLUIDS

108
CORRECT METHOD TO APPLY CUTTING FLUID

109
SURFACE FINISH
Surface finish, also known as surface
texture or surface topography.
It is the nature of a surface as defined
by the three characteristics of,
 Lay
 Surface roughness, and
 Waviness.

110
LAY DIRECTIONS

111
SYMBOL

112
MACHINABILITY
Machinability refers to the ease with which a metal can be
machined to an acceptable surface finish. Machinability defines,
Surface finish
Tool life
Force and power required
Difficulty level in chip control

113
MACHINABILITY - FACTORS
Work piece material
Cutting tool material
Process Parameters
Machining Environment

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