machining

Machining

ver. 1

ME 4210: Manufacturing Processes and Engineering Prof. J.S. Colton © GIT 2009

1

Old Machine Shop –

Edison’s lab


2

Machining = Chip formation by a toolg p y


3

Big lathe with big chipsBig lathe with big chips


4

Discontinuous chipsDiscontinuous chips


5

Continuous chipsContinuous chips


6

Machine Tools and ProcessesMachine Tools and Processes

• Turning • Filingg• Boring• Milling

• Sawing• Grinding• Milling

• PlaningGrinding

• ReamingH i• Shaping

• Broaching• Honing• Tappingg

• Drilling


7

Lathe (for turning)Lathe (for turning)


8

Lathe Parts


9

Typical Insert Cutting ToolTypical Insert Cutting Toolinsert

holder


10

Old Lathe


11


12

BoringBoring


13

Old Boring MachineOld Boring Machine


14

Old Planer


15

ShaperShaper


16

TrepanningTrepanning


17

DrillingDrilling(a)


18

MillingMilling


19

Face MillingFace Milling


20

Horizontal MillHorizontal Mill


21

Old Horizontal MillOld Horizontal Mill


22

Vertical Mill


23

Milling Typesg yp


24

Broach


25

Reamers


26bridge reamer

Honing


27

Thread Tap and DieThread Tap and Die

internal externalinternal external


28

Idealized Chip-formation ProcessOrthogonal Cutting

chip

cutting toolshear zone

workpiece


29

Chip-formation Geometryp y

chipprimary shear zone

tcBtool

to φζ

αtool

V (cutting velocity)ζ

Aworkpiece


30

Turning vs Orthogonal CuttingTurning vs. Orthogonal Cutting

Terminology used in a turning• Terminology used in a turning operation on a lathe, where f is the feed rate (in./rev or mm/rev) and d is the depth of cut.

• In turning the “orthogonality” is• In turning, the orthogonality is to the left in the drawing, hence a change of coordinate system is needed. If you were doing a diametral cut-off (plunge cut) (p g )operation, no change would be needed.

• Note that feed in turning is equivalent to the depth of cut in

th l tti d thorthogonal cutting, and the depth of cut in turning is equivalent to the width of cut in orthogonal cutting.


31

Cutting Force DiagramCutting Force Diagram

R

Vβ

αRFc

F N

F

φ

RFt

FsNs

N


32

Merchant’s Force CircleMerchant s Force CircleFs α

N

α

φβ−α

VFc

Ns

FtR

αβ α

βN

F

M Eugene Merchant


33

M. Eugene Merchant

3D Cutting (Oblique)3D Cutting (Oblique)Z

VcAαn

X, V αe

iO

Y


34

Typical Insert Cutting ToolTypical Insert Cutting Toolinsert

holder


35


36


37


38

Tool CoatingsTool Coatings


39

(b)(a) (c)Chip TypesBasic types of chips and their photomicrographs produced in metalproduced in metal cutting: (a) continuous chip with narrow, straight primary shear zone; (b) secondary shear zone at the

(f)(d) (e)

shear zone at the chip-tool interface; (c) continuous chip with built-up edge; (d) continuous chip with large primary shear zone; (e) segmented or nonhomogeneous chip and (f) discontinuous chip.discontinuous chip. Source: After M. C. Shaw, P. K. Wright, and S. Kalpakjian.


40

Chip TypesChip Types

• (a) Continuous chip with narrow primary• (a) Continuous chip with narrow primary shear zone– ductile materials at high speed

b d f t ti ( hi b k )– bad for automation (use chip breakers)• (b) Secondary shear zone at chip-tool

interface– increased energy dissipation

• (c) Continuous chip with built up edge (BUE)hi h l ti ki– high plastic working

– bad for automation


41

Chip TypesChip Types• (d) Continuous chip with large primary shear

zone– soft metals at low speeds and low rake angles

poor surface finish– poor surface finish– residual stresses

• (e) Segmented chip(e) Segmented chip– low thermal conductivity materials

• (f) Discontinuous chip– low ductility materials and/or negative rake angles– good for automation


42

Segmented chipsSegmented chips


43

Chip BreakerChip Breaker

hi chip breakerchip

cutting toolshear zone

chip breaker

cutting tool

workpiece


44

Integral Chip BreakersIntegral Chip Breakers


45

Tool MarksTool Marks


46

RoughnessRoughness

2

rfRoughnessAA 318

2

≈r

fRoughnesst 8

2≈

f f d

r318 r8

ff = feedr = nose radiusAA ith ti

f

AA = arithmetic averaget = peak-to-valley r


47

Surface MarksSurface Marks

(b)(a)

Surfaces produced on steel by cutting, as observed with a scanning electron microscope: (a) turned surface and (b) surface produced by shaping. Source: J. T. Black and S. Ramalingam.


48

Formation of Built up Edge (BUE)Formation of Built-up Edge (BUE)

chipBUEdeposit

cutting toolBUE

BUEdeposit

workpiece

deposit


49

Chatter• Results from vibration

T l b i d t f th• Tool bounces in and out of the workpiece


50

Glacial ChatterGlacial Chatter


51

Chip / Tool InterfaceChip / Tool Interface


52

Tool WearTool Wear(a) (b) (c)

Rake

( )(d)

Flank

(e)(d)


53

Taylor’s Equationy q

VTn = CV = cutting speedT = tool lifen, C = Taylor constants (empirical)

C

nFrederick W. Taylor

1856-1915

log V

log T1


54

1

F W Taylor’s ContributionsF.W. Taylor s Contributions

• Metal cutting• Metal cutting• Time / motion studies

Led to Congressional– Led to Congressional inquiry and banning of stop watch use by civil p yservants (1912-1949)

• Design of shovels• Scientific management


55

Cost componentsCost componentsTotal

Tool changing

OS

T

Min Tool

CO

Raw material

Machining

Material handling

CUTTING VELOCITY

Material handling


56

Cutting cost exampleCutting cost example HSS Carbide Carbide allVcm Vtm Vcm Vtm Vcm Vtm

N (rpm) 183 200 432 490 432 490T (min) 43 5 18 1 5 64 3 5 64 3T (min) 43.5 18.1 5.64 3 5.64 3Cm 3.1831 2.9125 1.3484 1.1888 1.3484 1.1888Cc 0.1463 0.3218 0.1793 0.2972 0.3495 0.3495Cg 0.2117 0.4655 0.1603 0.2657 0.3125 0.3125Ci 0.699 0.699 0.699 0.699 0.699 0.699Cs 0.05 0.05 0.05 0.05 0.05 0.05Cr 0.85 0.85 0.85 0.85 0.85 0.85Total ($) 5 14 5 30 3 29 3 35 3 61 3 45


57

Total ($) 5.14 5.30 3.29 3.35 3.61 3.45


58

machining

Documents