Manufacturing Technology I Lecture 3 - · PDF fileManufacturing Technology I Lecture 3 „Fundamentals of Cutting ... Which type of chip formation is existent, is generally affected

1

Manufacturing Technology I

Lecture 3

„„Fundamentals of CuttingFundamentals of Cutting““

Prof. Dr.-Ing. F. Klocke

Structure of the lecture

� Examples: turning of steel

� The cutting part - Terms and symbols

� The cutting operation

� Loads of the cutting part

� Influences exerted by the geometry of a cutting part on its characteristics under load

� Too wear

� Types of tool wear and tool wear measurements

� Wear mechanisms of the cutting process

� Summary

2







� Wear



� Summary

Example: turning of steel, roughing

source: Widia

3

Example: turning of steel, finishing

source: Widia







� Tool wear



� Summary

4

chip wedge

h

workpiece face flank

h chip thickness(prior to chip removal)

depth of cut(after chip removal)

hch

clearance angleαααα0

leading edge angleββββ0

effective cutting angleγγγγ0

hch

γγγγ0

ββββ0

αααα0

direction of cut

Terms at a simple cutting part

thickness of cut

chip thickness

tool orthogonal rake

tool orthogonal wedge angle

tool orthogonal clearance

( before deformation )

( after deformation )

transient surface

shaft

face

minor cutting edge

direction of cut

direction of feed

main cutting edge

face chamferof the major cutting edge

flank chamfer of the major cutting edge

main flank

cutting edge corner,with corner radius

minor flank

land of the minorcutting edge flank

Cutting edges and surfaces on the cutting part of a turning tool

source: ISO 3002/1

major cutting edge

shank

major first face

major first flank

major second flank

corner

minor second flank

minor first flank

major second face

5

Tool-in-hand system

source: ISO 3002/1

assumed

working plane Pf tool cutting edge

normal plane Pn

tool cutting edge

plane Ps

tool orthogonal plane Po

tool plane of

reference Pr

assumed direction of primary motion

tool back plane Pp

assumed direction of

feed motion

tool referenceplane Pr

base

selected point onthe cutting edge


assumed directionof feed motion

Tool-in-use system

source: ISO 3002/1

working plane Pfe

direction of feed

motion

direction of primary motion

Wirk-Rückebene

Ppe

working cutting edge

normal plane Pne = Pn


working referenceplane Pre

plane containing

base of tool

working cutting

edge plane Pse

working orthogonal

plane Poe

resultant cutting direction

direction offeed motion

working reference

plane Pre

resultant cutting direction

direction of primary motion

working plane Pfe

6

Engagement in longitudinal cylindrical turning

thickness of cut

cross-sectional area

primary motion

Angles at a selected point on the cutting edge

source: ISO 3002/1

direction of primary motion tool reference plane Pr

section C-D

assumed

working

plane Pf

section E-F

tool

referenceplane Pr

section A-B


major

cutting edge

section Z


tool back plane Pp

tool cutting edge

inclination

7







� Tool wear



� Summary

Chip formation

transient

surface

trace of the

shear plane

shear zone

material

cutting material

cross-sectional area

8

Strain rates of different manufacturing processes

strain rate

Superplastic Forming

Deep Drawing

Hot Rolling

Cold Rolling

Bar- and Tube-Drawing

High Speed Forging

Wire-Drawing

Explosive Forming

Split-Hopkinson-Bar-Test

Cutting

Process:

s/

1 ϕ&

410

−510

−1

110

210

310

− 210

− 110

− 310

410

510

610

710

strain tensor:

⋅

⋅=⋅

yxy

xyx

xy εγ

γεε

2

22

Calculation of the strain rate

⋅

⋅=⋅

yxy

xyx

ij εγ

γεε

2

22

oxy γψΦγ −+=

strain rate

x

vxx

∂

∂=ε&

shearing strain rate

y

vy

y∂

∂=ε&

z

vz

z∂

∂=ε&

x

v

y

v yxxy

∂

∂+

∂

∂=γ&

y

v

z

vzy

yz∂

∂+

∂

∂=γ&

z

v

x

v xzzx

∂

∂+

∂

∂=γ&

rate

of

de

form

ati

on

chvr

cvr

tool

workpiece

oγψΦ −+

yu

0x

h

chh

xu

xF

chx

yF

0=

=−+

ξ

γψΦch

xo

h

uarctan

strain tensor:

h

chh

hch

y

chx

h

h

x

x

λε

ε

==

=0

The outcome of the time derivation

is the strain rate!

workpiece

too

l

source: Leopold

ψ

Φ

hy lnt

λϕ∂

∂⋅= 2&

∂

∂⋅=

0

2x

xln

t

chxϕ&

⋅−+

−+⋅=

⋅−+

−+⋅

=⋅ho

ol

cho

och

xyln

ln

h

hln

x

xln

λγψΦ

γψΦλ

γψΦ

γψΦϕ

2

2

2

2

2 0

9

Types of chip formation

continuous chip segmented chip shearing chip

• very equal metallogra-

phic structure

• local hard deformed metallogra-

phic structure• local nearly no deformed metal-

lographic structure

• fractional seperation of segments

Which type of chip formation is existent, is generally affected by the friction on the face.

• local hard deformed me-

tallographical structure• local nearly no defor-

med metallographic

structure







� Tool wear



� Summary

10

Conditions of the cutting process

chip velocity

g

compressive

stress

shearing

stress

stress

characteristics

average shearing stress

average compressive stress

Components of the total force

primary motion

total force

back force

direction of feed motion

11

Influence of parameters on the components of the total force

back force Fp

depth of cut ap

blue brittleness

adhesion

Fc1.1‘ = 890 N/mm

thickness of cut h/mm

Cu

ttin

g f

orc

e F

c

wid

th o

f cu

t b

Fc‘/ N

/mm

Graphical determination of the parameters Fc1.1’ and (1-mc)

12

Distribution of effective work during the cutting process

source: Vieregge

7000

5000

4000

3000

2000

1000

Nm

wo

rkW

material

width of cut b

tool orthogonal clearance ααααo

tool orthogonal rake γγγγo

Distribution of heat and temperature in workpiece, chip and tool

m,

KmmK

TLL HS

µ

∆α∆

69

400 41

1066

=

⋅⋅⋅=

⋅⋅=

−

material

thickness of cut


chip

13

aluminium steel / titaniumfeed 0,25 mm 0,1 mmdepth of cut 2 mm 1 mm

0

100

200

300

N

500

cu

ttin

g f

orc

e F

cForce components and chip temperatures in turning

tem

pera

ture

cutting speed







� Tool wear



� Summary

14

Influence exerted by cutting edge geometry on machining parameters

low minimum thickness of cut

low:rn

to

decreasing weardecreasing

wear

to

to

to

decreasing wear

reduced chatter vibrations

lower cutting force

reduced theprobability

of chatter

vibrations

controlled

chip flow

increasing back

force and cutting

part stability

better surface

integrity

major first face







� Tool wear


� Wear mechanisms

� Summary

15

Types of tool wear and tool wear measurements

flank wear land

major flank wear land

tool orthogonal clearance


width of flank wear land

KF crater front distance

cutting edge offset in face

direction

cutting edge offset in flank

direction

c minor flank wear land

KF





� Loads to which the cutting part is exposed


� Tool wear


� Wear mechanisms in cutting processes

� Summary

16

Wear mechanisms in cutting processes

source: Vieregge

abrasion

oxidation

Comb and transverse crack formation in milling operations

source: Lehwald, Vieregge

width of flank wear land

17

Plastic deformation of the cutting edge

work material Ti Al 6V 4

tool material HS18 - 1 - 2 - 10

cutting speed vc = 8 m/min

cross-sectional area of cut ap·f=1,5 x 0,25 mm2

cutting time tc=1 min, cycles-to-failure N = 33 · 103

20 µm

α0γ0 λs χr εr rε

5o 8o -4o 75o 90o 0,5mm

cutting part geometry

8° 10° -4° 90° 60° 1 mm

α0 γ0 λ0 ε0 κ0rε


cutting time tc = 30 min

Flank wear and formation of build-up cutting edge

vc = 2 m/min

vc = 10 m/min

vc = 20 m/min

0,1 mm

vc = 30 m/min vc = 40 m/min

HW-P30

formation of

build-up cuttingedges

wid

th o

f fl

an

k w

ear

lan

d

sλ rε εrrκoα oγ

18

Flank wear at turning tools



material Ck53N

cutting material HS12-1-4-5

depth of cut ap=2mm

cutting speed vc

wid

th o

f fl

an

k w

ear

lan

d V

B

α0γ0 λs χr εr rε

8o 10o -4o 90o 60o 1 mm

f = 0,4 mm

f = 0,25 mm

f = 0,1 mm

0,24

0,20

0,16

0,12

0,08

0,04

04 7 10 20 40 m/min 100

mm

steel C10steel Ck53

cemented carbide P30cemented carbide P30

Zone A: Fe-Co-MK

chip

tool

solution of WC to:

C CFe Co

A

B

TiC - WC (TaC/NbC)

Co – WC - solid solutionFe3W3C; (FeW)6C; (FeW)23C6 Zone B: Co-Fe-MK

Simplified representation of diffusion process in cemented carbide tools

case hardenedquenched and tempered

19

Oxidation zones of a cemented carbide turning tool

oxidation

face

oxidation zones

flank

material Ck53N

cutting material HC-P30cutting speed vc = 125 m/min

cross-sectional area ap · f = 3 · 0,25 mm²








� Tool wear


� Wear mechanisms in cutting processes

� Summary

20

� Identify the different cutting edges and areas of a turning tool!

� Specify and explain the angles for determination of the orientation and shape of the cutting part!

� Specify the types of chip formation and explain their development!

� In which plane do you measure the tool angles?

� List the orthogonal components of the total force!

� Illustrate qualitatively the dependence of feed, cutting speed, cutting depth and tool cutting edge angle on the total force components! Explain the dependence!

� Specify an empirical force equation and explain the characteristic parameters!

� Where can you identify heat sources during chip formation and how dissipates the major heat? Please identify the place of the highest cutting temperature?

List of questions I

� Specify the influencing factors for choosing the geometry of the cutting part!

� How to increase the stability of the cutting edge?

� Specify the influencing variables to reduce the probability for chatter vibrations!

� Identify and explain the types of tool wear at the cutting part!

� Signify the major tool wear measurements!

� Specify the wear mechanisms and indicate their dependence of the cutting speed.

� Explain comb and transverse crack formation!

� Illustrate the term „built-up edge formation“ and explain the progression of the flank wear land and the surface roughness dependent on the cutting speed!

List of questions II

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Manufacturing Technology I Lecture 3 - · PDF fileManufacturing Technology I Lecture 3 „Fundamentals of Cutting ... Which type of chip formation is existent, is generally affected