6.Cutting

8/7/2019 6.Cutting

http://slidepdf.com/reader/full/6cutting 1/83

Technion – Israel Institute of Technology

6. Cutting

Department of Mechanical Engineering

034030 Manufacturing Processes

8/7/2019 6.Cutting


2Common Cutting Processes

8/7/2019 6.Cutting


3Factors Influencing Cutting Process

8/7/2019 6.Cutting


4Turning Operation

8/7/2019 6.Cutting


5Two-Dimensional Cutting Process

)cos(

sin

α φ

φ

−

==c

o

t

t r

Cutting ratio:

8/7/2019 6.Cutting


6Chip Formation

V s =γ &

Shear-strain rate:

( ) φ α α φ sincoscosc s

V V V ==

−

8/7/2019 6.Cutting


7Types of Chips

C o n t i n

u o u s w i t h

n a r r o w

s h e a r z o n e

C o n t i n u o u s w i t h

b u i l t - u p e d g e

S e

g m e n t e d

D i s c o

n t i n u o u s

8/7/2019 6.Cutting


8Built-up Edge

S u r f a c e f i n i s h i n t u r n i n g

S u r f a c e f i n i s h i n m i l l i n g

8/7/2019 6.Cutting


9Chip Breakers

8/7/2019 6.Cutting


10Oblique Cutting

8/7/2019 6.Cutting


11Cutting Tool

8/7/2019 6.Cutting


12Forces Acting on a Cutting Tool

Fc -cutting forceFt - thrust force

R - resultant force

F - friction force,

N - normal forceβ- friction angle

Fs - shear forceFn- normal force

( ) ( )

( ) ( )

α

α

β µ

α β φ α β φ

α β α β β β

tan

tan

tan

sin;cos

sin;coscos ;sin

t c

c t

n s

t c

F F

F F

N

F

R F R F

R F R F R N R

−

+

===

−+=−+=

−=−===

8/7/2019 6.Cutting


13Thrust Force

( )α β −= tanc t F F

Note that at high rake angles,the thrust force may benegative, which has importantimplications in the design ofmachine tools and incontrolling the stability of the

cutting process

AISI 1112cold-rolledsteel

8/7/2019 6.Cutting


14Shear and Normal Stresses

φ sinAs

o t w

=

o

s

s

s

t w

F

A

F φ τ sin==

o

n

s

n

t w

F

A

F φ σ

sin==

Area of the shear plane:

Average shear stress:

Average normal stress:

8/7/2019 6.Cutting


15Shear-Angle Relationships

( )

( )α β

φ α β φ τ

−

−+==

cos

sincos

o

c

s

s

t w

F

A

F

Merchant model:

( ) ( )

2245

0

β α

φ

φ α β φ φ α β φ φ

τ

−+=

=−+−−+=

o

d

d sinsincoscos

If we assume that β is independent of φ

M e r c h a n t m o d e l

8/7/2019 6.Cutting


16Specific Energy

m se f s

o

c

o

c t

c

u u u u t w F

V t w V F u

V F

+++===

=

:removedmaterialofvolumeunitperenergyTotal

cuttingininputpowerTotal

Surface energy, u se

, resulted from the for-mation of 2 new surfaces can be neglected;

energy of momentum change , u m , can besignificant at cutting speeds above 125 m/s.

( )

o

t c

o o

c

f t w

r F F

t w

Fr

V t w

FV

u

α α cossin

:frictionforenergySpecific

+===

V t w

V F u

o

s s s =

:shearingforenergySpecific

8/7/2019 6.Cutting


17Temperatures in Cutting

• Sources of heat generation◦ Shear zone◦ Chip-tool interface◦ Tool-workpiece interface

• Effects of the temperature rise◦ Reduces the strength, hardness,

and wear resistance of thecutting tool

◦

Causes dimensional changes inthe part being machined, makingcontrol of accuracy difficult

◦ Can induce thermal damage tothe machined surface, affectingits properties and service life

8/7/2019 6.Cutting


18Tool Wear Patterns

8/7/2019 6.Cutting


19Tool Wear

Flank face

Rake face

Crater wear

Flank face

Rake face

Flank wear

Flank face

BUE

Rake face

Thermal

cracking

8/7/2019 6.Cutting


20Flank Wear

8/7/2019 6.Cutting


21Taylor Tool-Life Curves

.Const T n =

Taylor equation:

8/7/2019 6.Cutting


22Crater Wear

1) High-speed steel2) C-1 carbide3) C-5 carbide

8/7/2019 6.Cutting


23Chipping

8/7/2019 6.Cutting


24Tool-Condition Monitoring

8/7/2019 6.Cutting


25Machined Surfaces

• Factors affecting surface integrity◦ Temperatures generated during

processing◦ Residual stresses◦ Metallurgical transformations◦ Plastic deformation, tearing and

cracking

P r

o d u c e d b y t

u r n i n g

P r o d u c e d b y s

h a p i n g

8/7/2019 6.Cutting


26Properties of Cutting Tool Materials

8/7/2019 6.Cutting


27Hardness of Cutting Tools

8/7/2019 6.Cutting


28Coated Tools

Typical wear patterns of high-

speed-steel uncoated andtitanium-nitride coated tools

Multiphase coatings on atungsten-carbide substrate

8/7/2019 6.Cutting


29Carbide Inserts and Toolholders

8/7/2019 6.Cutting


30Insert Edge Strength

8/7/2019 6.Cutting


31Cubic Boron Nitride Inserts

Inserts with polycrystallinecubic boron nitride tips (toprow), and solid-polycrystalline

cBN inserts (bottom row)

8/7/2019 6.Cutting


32Historical Tool Improvement

8/7/2019 6.Cutting


33Cutting Fluids

• Positive effects◦ Reduce friction and wear, hence improving tool life and surface finish

◦ Reduce forces and energy consumptions◦ Cool the cutting zone, thus reducing workpiece temperature and

distortion and improving tool life◦ Wash away chips◦

Protect the newly machined surfaces from environmental corrosion

• Negative effects◦ Increase the extent of alternate heating and cooling in interrupted

cutting operations, such as milling, and can cause thermal fatigue◦ May cause the chip to become curlier, thus concentrating the stresses

and heat near the tool tip, reducing the tool life◦ Can represent biological and environmental hazard

34

8/7/2019 6.Cutting


34Proper Application of Cutting Fluids

35

8/7/2019 6.Cutting


35Characteristics of Machining

36

8/7/2019 6.Cutting


36Production Rates

37

8/7/2019 6.Cutting


37Lathe Operations

38

8/7/2019 6.Cutting


38Components of a Lathe

39

8/7/2019 6.Cutting


39Numerical-Control Lathe and Turret

40

8/7/2019 6.Cutting


40Collets

8/7/2019 6.Cutting


42T i O i

8/7/2019 6.Cutting


42Turning Operation

43Ri h H d T l A l

8/7/2019 6.Cutting


43Right-Hand Tool Angles

44C i S d f T i

8/7/2019 6.Cutting


44Cutting Speeds for Turning

45T i l CNC P t

8/7/2019 6.Cutting


45Typical CNC Parts

46M hi i f C l Sh

8/7/2019 6.Cutting


46Machining of Complex Shapes

47C tti S Th d

8/7/2019 6.Cutting


47Cutting Screw Threads

48Ch d Di f Th d C tti

8/7/2019 6.Cutting


48Chasers and Die for Thread Cutting

49T i

8/7/2019 6.Cutting


49Tapping

50B i d B i Mill

8/7/2019 6.Cutting


50Boring and Boring Mill

51D illi g d R mi g O ti

8/7/2019 6.Cutting


51Drilling and Reaming Operations

52Types of Drills

8/7/2019 6.Cutting


52Types of Drills

53Trepanning

8/7/2019 6.Cutting


53Trepanning

54Reamers

8/7/2019 6.Cutting


54Reamers

55Drilling Machines

8/7/2019 6.Cutting


55Drilling Machines

56Shapes Made with Multi Tooth Tools

8/7/2019 6.Cutting


Shapes Made with Multi-Tooth Tools

57Basic Types of Milling Cutters

8/7/2019 6.Cutting


Basic Types of Milling Cutters

58Peripheral Milling

8/7/2019 6.Cutting


Peripheral Milling

59Peripheral Cutters

8/7/2019 6.Cutting


Peripheral Cutters

60Face Milling

8/7/2019 6.Cutting


Face Milling

61Face Milling Cutter

8/7/2019 6.Cutting


Face Milling Cutter

62Position of Cutter in Face Milling

8/7/2019 6.Cutting


Position of Cutter in Face Milling

63Effect of Insert Shape on Feed Marks

8/7/2019 6.Cutting


Effect of Insert Shape on Feed Marks

64Surface Features in Face Milling

8/7/2019 6.Cutting


Surface Features in Face Milling

65Edge Defects in Face Milling

8/7/2019 6.Cutting


Edge Defects in Face Milling

8/7/2019 6.Cutting


67Ball Nose End Mills

8/7/2019 6.Cutting


Ball Nose End Mills

68Column-and-Knee Milling Machines

8/7/2019 6.Cutting


Column and Knee Milling Machines

69CNC Milling Machines

8/7/2019 6.Cutting


CNC Milling Machines

70Planing and Shaping

8/7/2019 6.Cutting


Planing and Shaping

71Typical Parts Made by Broaching

8/7/2019 6.Cutting


Typical Parts Made by Broaching

72Broaching

8/7/2019 6.Cutting


Broaching

73Chipbreaker Features on Broaches

8/7/2019 6.Cutting


Chipbreaker Features on Broaches

Flat broach

Round broach

74Sawing Operation

8/7/2019 6.Cutting


Sawing Operation

75Saw Teeth

8/7/2019 6.Cutting


Saw Teeth

76Gear Cutting

8/7/2019 6.Cutting


Gear Cutting

77Parts Made on Machining Centers

8/7/2019 6.Cutting


Parts Made on Machining Centers

78Horizontal-Spindle Machining Center

8/7/2019 6.Cutting


Horizontal Spindle Machining Center

79Swing-Around Tool Changer

8/7/2019 6.Cutting


Swing Around Tool Changer

8/7/2019 6.Cutting


81Hexapod Machining Center

8/7/2019 6.Cutting


p g

82Chatter and Vibration

8/7/2019 6.Cutting


83Economics of Machining

8/7/2019 6.Cutting


g

( )[ ]n c

o

T n

C V

11 −=

/

Optimum cutting speed:

( )

timechanging

tooltheisTwhere

/

c

c o T n T 11 −=

Optimum tool life:

Documents

6.Cutting