(a) Straight turning (b) Cutting of f Common Machining ... · PDF fileManufacturing Processes...

Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid© 2008, Pearson EducationISBN No. 0-13-227271-7

Common Machining Processes

FIGURE 8.1 Some examples of common machining processes.

(c) Slab milling (d) End milling

End mill

Cutter

(b) Cutting off(a) Straight turning

ToolTool


Orthogonal Cutting

FIGURE 8.2 Schematic illustration of a two-dimensional cutting process, or orthogonal cutting. (a) Orthogonal cutting with a well-defined shear plane, also known as the Merchant model; (b) Orthogonal cutting without a well-defined shear plane.

Rake angle

Chip

Tool face

V Flank

Relief orclearanceangle

Shear angle

Shear plane

!

Tool

Shiny surfaceRough surface

Workpiece

to

tc

- +

"

(a)

Chip

Roughsurface

Primaryshear zone Flank

Relief orclearanceangle

Tool face

Tool

tc

to

V

- +

"

Rake angle

(b)

Rough surface


Chip Formation

FIGURE 8.3 (a) Schematic illustration of the basic mechanism of chip formation in cutting. (b) Velocity diagram in the cutting zone.

Shear plane

Workpiece

d

Chip

Tool

A C

B

A C

B O

Rake angle,

(b)

Vc

Vs

V

(a)

(90° - )

(90° - + )

( - )

( - )


Types of Chips

FIGURE 8.4 Basic types of chips produced in metal cutting and their micrographs: (a) continuous chip with narrow, straight primary shear zone; (b) secondary shear zone at the tool-chip interface; (c) continuous chip with built-up edge; (d) segmented or nonhomogeneous chip; and (e) discontinuous chip. Source: After M.C. Shaw, P.K. Wright, and S. Kalpakjian.

(e)(d)

(a) (b) (c)

Tool

WorkpiecePrimary

shearzone

Chip

Primaryshear zone

Chip

Tool

Secondary shear zones

BUE

Lowshearstrain

Highshearstrain

FIGURE 8.5 Shiny (burnished) surface on the tool side of a continuous chip produced in turning.


Hardness in Cutting Zone

FIGURE 8.6 (a) Hardness distribution in the cutting zone for 3115 steel. Note that some regions in the built-up edge are as much as three times harder than the bulk workpiece. (b) Surface finish in turning 5130 steel with a built-up edge. (c) Surface finish on 1018 steel in face milling. Source: Courtesy of Metcut Research Associates, Inc.

(a)

(b)

(c)

474

661

588

492

588

656 604

684

565

432589

656 567 578

512704

704 639

655770734

466

587704

372306

329

289325

331286

289

371 418

383

306386

261

565327

361281

289

410341

281308

231

201

251266

317229

377503544409297

316

230

Workpiece

Built-upedge

Hardness (HK)

Chip


Chip Breakers

FIGURE 8.7 (a) Schematic illustration of the action of a chip breaker. Note that the chip breaker decreases the radius of curvature of the chip. (b) Chip breaker clamped on the rake face of a cutting tool. (c) Grooves on the rake face of cutting tools, acting as chip breakers. Most cutting tools now are inserts with built-in chip-breaker features.

(a) (b)

Workpiece

Tool

After

Chip

Before

Chip breaker

Rake faceof tool

Tool

Clamp

Chip breaker

(c)

Positive rake

Rake face

0° rakeRadius

FIGURE 8.8 Various chips produced in turning: (a) tightly curled chip; (b) chip hits workpiece and breaks; (c) continuous chip moving radially outward from workpiece; and (d) chip hits tool shank and breaks off. Source: After G. Boothroyd. (a) (b) (c) (d)


Oblique Cutting

FIGURE 8.9 (a) Schematic illustration of cutting with an oblique tool. (b) Top view, showing the inclination angle, i. (c) Types of chips produced with different inclination angles.

Workpiecei = 30°

i = 15°

i = 0°

Chip

(a) (b) (c)

i

a

o

Tool

Top view

Workpiece

i

a

o

Tool

Chip

y

z

x

c

t


Right-Hand Cutting Tool

FIGURE 8.10 (a) Schematic illustration of a right-hand cutting tool for turning. Although these tools have traditionally been produced from solid tool-steel bars, they are now replaced by inserts of carbide or other tool materials of various shapes and sizes, as shown in (b).

(a) (b)

End-cuttingedge angle

(ECEA)

Side-rakeangle, + (SR)

Axis

Axis

Cutting edge

Face

Back-rake angle, + (BR)

Nose radius

Flank

Side-relief angle

Side-cutting edge angle (SCEA)

Clearance or end-relief angle

AxisSha

nk

Insert

Clamp

Clamp screw

Toolholder

Seat or shim


Cutting Forces

FIGURE 8.11 (a) Forces acting on a cutting tool in two-dimensional cutting. Note that the resultant forces, R, must be collinear to balance the forces. (b) Force circle to determine various forces acting in the cutting zone. Source: After M.E. Merchant.

Chip

Tool

Workpiece

(a) (b)

Fn

Fc

Fs

Ft

R

F

N

R

Chip

V

V

Tool

Workpiece

Fc

Fs

FtF

N

R

Cutting force Friction coefficient

Fc = Rcos(β!α) =wtoτcos(β!α)

sinφcos(φ+β!α)µ= tanβ=

Ft +Fc tanαFc!Ft tanα


Cutting Data

FIGURE 8.12 Thrust force as a function of rake angle and feed in orthogonal cutting of AISI 1112 cold-rolled steel. Note that at high rake angles, the thrust force is negative. A negative thrust force has important implications in the design of machine tools and in controlling the stability of the cutting process. Source: After S. Kobayashi and E.G. Thomsen.

! = 5°

10°

15°

20°

25°

30°

35°

40°

0 0.1 0.2 0.3

mm/revmm/rev

800

400

0

2200

(N)

Ft (

lb)

200

150

100

50

0

2500 0.002 0.004 0.006 0.008 0.010 0.012

Feed (in./rev)

ut

(in.-lb/in3 uf/ut

! " # µ $ Fc (lb) Ft (lb) !103) us uf (%)25! 20.9! 2.55 1.46 56 380 224 320 209 111 3535 31.6 1.56 1.53 57 254 102 214 112 102 4840 35.7 1.32 1.54 57 232 71 195 94 101 5245 41.9 1.06 1.83 62 232 68 195 75 120 62to = 0.0025 in.; w = 0.475 in.; V = 90 ft/min; tool: high-speed steel.

uf/ut

! V " # µ $ Fc Ft ut us uf (%)+10 197 17 3.4 1.05 46 370 273 400 292 108 27

400 19 3.1 1.11 48 360 283 390 266 124 32642 21.5 2.7 0.95 44 329 217 356 249 107 301186 25 2.4 0.81 39 303 168 328 225 103 31

-10 400 16.5 3.9 0.64 33 416 385 450 342 108 24637 19 3.5 0.58 30 384 326 415 312 103 251160 22 3.1 0.51 27 356 263 385 289 96 25

to = 0.037 in.; w = 0.25 in.; tool: cemented carbide.

TABLE 8.1 Data on orthogonal cutting of 4130 steel.

TABLE 8.2 Data on orthogonal cutting of 9445 steel.


Shear Force & Normal Force

FIGURE 8.13 (a) Shear force and (b) normal force as a function of the area of the shear plane and the rake angle for 85-15 brass. Note that the shear stress in the shear plane is constant, regardless of the magnitude of the normal stress, indicating that the normal stress has no effect on the shear flow stress of the material. Source: After S. Kobayashi and E.G. Thomsen.

= 20° to 40°

800

400

0

= 50,000 psi

0 1 32 4 5 6

0 1 32

1200

320

280

240

200

160

120

80

40

0

mm2

(N)

As (in2 x 10-3)

Fs (

lb)

(a)

0 1 32 4 5 6

0 1 32

1200

320

280

240

200

160

120

80

40

0

800

400

As (in2 x 10-3)

mm2

(N)

Ft (lb)

(b)

25

303540

20°


Shear Stress on Tool Face

FIGURE 8.14 Schematic illustration of the distribution of normal and shear stresses at the tool-chip interface (rake face). Note that, whereas the normal stress increases continuously toward the tip of the tool, the shear stress reaches a maximum and remains at that value (a phenomenon known as sticking; see Section 4.4.1).

!

"

Tool face

Sliding

Sticking

Stresses on tool face

Tool tip

Tool

Flank face


Shear-Angle Relationships

FIGURE 8.15 (a) Comparison of experimental and theoretical shear-angle relationships. More recent analytical studies have resulted in better agreement with experimental data. (b) Relation between the shear angle and the friction angle for various alloys and cutting speeds. Source: After S. Kobayashi.

50

40

30

20

10

0230 220 210 0 10 20 30 40 50 60

Lead

Copper

Tin

Eq. (8.21)

Eq. (8.20)

Mild steel

Alum

inum

(! - ")

Sh

ea

r a

ng

le, # (

de

g.)

" = 0

! = 10 30 50 70 (deg.)

µ=0 0.5 1 2

60

40

20

0

# (

de

g.)

(a) (b)

Merchant [Eq. (8.20)]

Shaffer [Eq. (8.21)]

Mizuno [Eqs. (8.22)-(8.23]

φ= 45!+α2" β2

φ= 45!+α"β

φ= α for α> 15!

φ= 15! for α< 15!


Specific Energy

Specific Energy∗

Material W-s/mm3 hp-min/in3

Aluminum alloys 0.4-1.1 0.15-0.4Cast irons 1.6-5.5 0.6-2.0Copper alloys 1.4-3.3 0.5-1.2High-temperature alloys 3.3-8.5 1.2-3.1Magnesium alloys 0.4-0.6 0.15-0.2Nickel alloys 4.9-6.8 1.8-2.5Refractory alloys 3.8-9.6 1.1-3.5Stainless steels 3.0-5.2 1.1-1.9Steels 2.7-9.3 1.0-3.4Titanium alloys 3.0-4.1 1.1-1.5∗ At drive motor, corrected for 80% e!ciency; multiplythe energy by 1.25 for dull tools.

TABLE 8.3 Approximate Specific-Energy Requirements in Machining Operations


Temperatures in Cutting400

500

450

Workpiece

Tool

Chip

3080

130

380

600360

500

600

650

700

Temperature (°C)

650

600

FIGURE 8.1 Typical temperature distribution in the cutting zone. Note the severe temperature gradients within the tool and the chip, and that the workpiece is relatively cool. Source: After G. Vieregge.

200

300

V = 550 ft/min

Work material: AISI 52100

Annealed: 188 HB

Tool material: K3H carbide

Feed: 0.0055 in./rev

(0.14 mm/rev)

0 0.5 1.0 1.5

mm

700

600

500

400

°C

0 .008 .016 .024 .032 .040 .048 .056

Distance from tool tip (in.)

1400

1300

1200

1100

1000

900

800

700

Fla

nk s

urf

ace

te

mp

era

ture

(°F

)

(a)

55

0 f

t/m

in

300

200

2000

1800

1600

1400

1200

1000

800

600

400

Lo

ca

l te

mp

era

ture

at

too

l-ch

ip in

terf

ace

(°F

)

0 0.2 0.4 0.6 0.8 1.0

Fraction of tool-chipcontact length measured

in the direction of chip flow

1100

900

700

500

300

°C

(b)

FIGURE 8.2 Temperature distribution in turning as a function of cutting speed: (a) flank temperature; (b) temperature along the tool-chip interface. Note that the rake-face temperature is higher than that at the flank surface. Source: After B.T. Chao and K.J. Trigger.

T =1.2Yfρc

3

√VtoK

FIGURE 8.18 Proportion of the heat generated in cutting transferred to the tool, workpiece, and chip as a function of the cutting speed. Note that most of the cutting energy is carried away by the chip (in the form of heat), particularly as speed increases.

Workpiece

Cutting speed

En

erg

y (

%)

Tool

Chip


Terminology in Turning

FIGURE 8.19 Terminology used in a turning operation on a lathe, where f is the feed (in mm/rev or in./rev) and d is the depth of cut. Note that feed in turning is equivalent to the depth of cut in orthogonal cutting (see Fig. 8.2), and the depth of cut in turning is equivalent to the width of cut in orthogonal cutting. See also Fig. 8.42.

Depth of cut(mm or in.)

Feed(mm/rev or in./rev)

Tool

Chip


Tool Wear

FIGURE 8.20 Examples of wear in cutting tools. (a) Flank wear; (b) crater wear; (c) chipped cutting edge; (d) thermal cracking on rake face; (e) flank wear and built-up edge; (f) catastrophic failure (fracture). Source: Courtesy of Kennametal, Inc.

Flank face

Rake face

Flank wear

Flank face

BUE

Rake face

Crater wear

Flank face

Rake face

Thermal

cracking

(b)

(d)

(c)

(e)

(a)

Rakeface

Craterweardepth(KT)

Flankwear

Flankface

Tool

Rake faceCraterwear

Depth-of-cut line

Noseradius

R

Flank wearDepth-of-cut line

VBmaxVB

Flank face

Taylor tool life equation:

VTn =C

High-speed steels 0.08-0.2Cast alloys 0.1-0.15Carbides 0.2-0.5Ceramics 0.5-0.7

TABLE 8.4 Range of n values for various cutting tools.


Effect of Workpiece on Tool Life

FIGURE 8.21 Effect of workpiece microstructure on tool life in turning. Tool life is given in terms of the time (in minutes) required to reach a flank wear land of a specified dimension. (a) Ductile cast iron; (b) steels, with identical hardness. Note in both figures the rapid decrease in tool life as the cutting speed increases.

Hardness(HB) Ferrite Pearlite

a. As cast

b. As cast

c. As cast

d. Annealed

e. Annealed

265

215

207

183

170

20%

40

60

97

100

80%

60

40

3_

50

100 300 500 700 900

100 150 200 250

0

40

80

120

m/min

Cutting speed (ft/min)

To

ol lif

e (

min

)a

b cd

e

(a)

Pearlite

-ferrite

Marte

nsitic

Spheroidized

0.1 0.2 0.3 0.4

m/s

(b)

100

80

60

40

20

0

To

ol lif

e (

min

)

20 30 40 50 60 70 80 90



Tool-Life Curves

FIGURE 8.22 (a) Tool-life curves for a variety of cutting-tool materials. The negative inverse of the slope of these curves is the exponent n in tool-life equations. (b) Relationship between measured temperature during cutting and tool life (flank wear). Note that high cutting temperatures severely reduce tool life. See also Eq. (8.30). Source: After H. Takeyama and Y. Murata.

300

50 300

m/min

3000

100

300

100

10

20

Tool lif

e (

min

)

5

110,00050001000


n

Hig

h-s

peed s

teel

Cast a

lloy

Carb

ide

Ceram

ic

Feed constant,speed variable

Speed constant,feed variable

800 1000 1200 1400

°C

400200

100

6040

20

10

642

1

0.6

0.2

Tool lif

e (

min

)

1500 1800 2100 2400

Temperature (°F)

Work material: Heat-resistant alloyTool material: Tungsten carbideTool life criterion: 0.024 in. (0.6 mm) flank wear

(a) (b)


Tool Wear

FIGURE 8.23 Relationship between crater-wear rate and average tool-chip interface temperature in turning: (a) high-speed-steel tool; (b) C1 carbide; (c) C5 carbide. Note that crater wear increases rapidly within a narrow range of temperature. Source: After K.J. Trigger and B.T. Chao.

Average tool-chip interfacetemperature (°F)

800 1200 1600 2000

0.15

0.3020

500 700 900 1100

10

0 0

°C

mm

3/m

in

Cra

ter

we

ar

rate

(in

3/m

in x

10-6

) a b c

Allowable Wear Land (mm)Operation High-Speed Steels CarbidesTurning 1.5 0.4Face milling 1.5 0.4End milling 0.3 0.3Drilling 0.4 0.4Reaming 0.15 0.15

TABLE 8.5 Allowable average wear lands for cutting tools in various operations.

Rake face

Crater wear

Chip Flank face

FIGURE 8.23 Interface of chip (left) and rake face of cutting tool (right) and crater wear in cutting AISI 1004 steel at 3 m/s (585 ft/min). Discoloration of the tool indicates the presence of high temperature (loss of temper). Note how the crater-wear pattern coincides with the discoloration pattern. Compare this pattern with the temperature distribution shown in Fig. 8.16. Source: Courtesy of P.K. Wright.


Acoustic Emission and Wear

FIGURE 8.25 Relationship between mean flank wear, maximum crater wear, and acoustic emission (noise generated during cutting) as a function of machining time. This technique has been developed as a means for continuously and indirectly monitoring wear rate in various cutting processes without interrupting the operation. Source: After M.S. Lan and D.A. Dornfeld.

Crater wear

Flank wear

0.005

0.0040.003

0.002

0.0010

in. mm

0.15

0.1

0.05

0

Ma

xim

um

cra

ter

de

pth

Me

an

fla

nk w

ea

r

1.5

1.0

0.5

0

mm in.

Me

an

RM

S (

mV

)

0.0500.0400.0300.020

0.010

1500

1000

500

0

0 10 20 30 40 50 60

Elapsed machining time (min)


Surface Finish

FIGURE 8.26 Range of surface roughnesses obtained in various machining processes. Note the wide range within each group, especially in turning and boring. (See also Fig. 9.27).

Flame cutting

Snagging (coarse grinding)

Sawing

Planing, shaping

Drilling

Chemical machining

Electrical-discharge machining

Milling

Broaching

Reaming

Electron-beam machining

Laser machining

Electrochemical machining

Turning, boring

Barrel finishing

Electrochemical grinding

Roller burnishing

Grinding

Honing

Electropolishing

Polishing

Lapping

Superfinishing

Process 2000 1000 500 250 125 63 32 16 8 4 2 1 0.550 25 12.5 6.3 3.2 1.6 0.8 0.40 0.20 0.10 0.05 0.025 0.012

Roughness (Ra)

µin.

µm

Average application

Less frequent application

Sand casting

Die casting

Hot rolling

Forging

Permanent mold casting

Investment casting

Extruding

Cold rolling, drawing

Rough cutting

Casting

Forming

Machining

Advanced machining

Finishing processes


Surfaces in Machining

FIGURE 8.27 Surfaces produced on steel in machining, as observed with a scanning electron microscope: (a) turned surface, and (b) surface produced by shaping. Source: J.T. Black and S. Ramalingam.

(a) (b)

FIGURE 8.28 Schematic illustration of a dull tool in orthogonal cutting (exaggerated). Note that at small depths of cut, the rake angle can effectively become negative. In such cases, the tool may simply ride over the workpiece surface, burnishing it, instead of cutting.

Incre

asin

g d

epth

of cut

Workpiece Machinedsurface

Tool


Inclusions in Free-Machining Steels

FIGURE 8.29 Photomicrographs showing various types of inclusions in low-carbon, resulfurized free-machining steels. (a) Manganese-sulfide inclusions in AISI 1215 steel. (b) Manganese-sulfide inclusions and glassy manganese-silicate-type oxide (dark) in AISI 1215 steel. (c) Manganese sulfide with lead particles as tails in AISI 12L14 steel. Source: Courtesy of Ispat Inland Inc.

(a) (b) (c)


Hardness of Cutting Tools

FIGURE 8.30 Hardness of various cutting-tool materials as a function of temperature (hot hardness). The wide range in each group of tool materials results from the variety of compositions and treatments available for that group.

055

60

65

70

75

80

85

90

95100 300 500 700

200 400 600 800 1000 1200 1400

20

25

30

35

40

45

50

55

60

65

70

Ha

rdn

ess (

HR

A)

HR

C

Temperature (°F)

°C

Ceramics

Carbides

Hig

h-sp

eed ste

els

Cast alloys

Carbon too

l steels


Tool Materials

CarbidesCubic Single

High-Speed Cast Boron CrystalProperty Steel Alloys WC TiC Ceramics Nitride Diamond!

Hardness 83-86 HRA 82-84 HRA 90-95 HRA 91-93 HRA 91-95 HRA 4000-5000 HK 7000-8000 HKCompressive strength

MPa 4100-4500 1500-2300 4100-5850 3100-3850 2750-4500 6900 6900psi !103 600-650 220-335 600-850 450-560 400-650 1000 1000

Transverse rupturestrength

MPa 2400-4800 1380-2050 1050-2600 1380-1900 345-950 700 1350psi !103 350-700 200-300 150-375 200-275 50-135 105-200

Impact strengthJ 1.35-8 0.34-1.25 0.34-1.35 0.79-1.24 < 0.1 < 0.5 < 0.2in.-lb 12-70 3-11 3-12 7-11 < 1 < 5 < 2

Modulus of elasticityGPa 200 — 520-690 310-450 310-410 850 820-1050psi !106 30 — 75-100 45-65 45-60 125 120-150

Densitykg/m3 8600 8000-8700 10,000-15,000 5500-5800 4000-4500 3500 3500lb/in3 0.31 0.29-0.31 0.36-0.54 0.2-0.22 0.14-0.16 0.13 0.13

Volume of hardphase (%) 7-15 10-20 70-90 — 100 95 95

Melting or decom-position temperature"C 1300 — 1400 1400 2000 1300 700"F 2370 — 2550 2550 3600 2400 1300

Thermal conductivity,W/mK 30-50 — 42-125 17 29 13 500-2000

Coe!cient of thermalexpansion, !10#6/"C 12 — 4-6.5 7.5-9 6-8.5 4.8 1.5-4.8

! The values for polycrystalline diamond are generally lower, except impact strength, which is higher.

TABLE 8.6 Typical range of properties of various tool materials.


Properties of Tungsten-Carbide Tools

FIGURE 8.31 Effect of cobalt content in tungsten-carbide tools on mechanical properties. Note that hardness is directly related to compressive strength (see Section 2.6.8) and hence, inversely to wear [see Eq. (4.6)].

We

ar

(mg

), c

om

pre

ssiv

e a

nd

tra

nsve

rse

-

rup

ture

str

en

gth

(kg

/mm

2)

Cobalt content (% by weight)

Vic

ke

rs h

ard

ne

ss (

HV

)

600

500

400

300

200

100

00 5 10 15 20 25 30

1750

1500

1250

1000

750

500

HRA 92.4

90.5

88.5

85.7

Compressive strengthHardness

Wear

Transverse-rupture strength


Inserts

FIGURE 8.32 Methods of mounting inserts on toolholders: (a) clamping, and (b) wing lockpins. (c) Examples of inserts mounted using threadless lockpins, which are secured with side screws. Source: Courtesy of Valenite.

(c)(b)

Shank

Seat

Lockpin

Insert

(a)

Insert

Clamp

Clampscrew

Seator shim

Toolholder


Insert Strength

FIGURE 8.33 Relative edge strength and tendency for chipping and breaking of inserts with various shapes. Strength refers to that of the cutting edge shown by the included angles. Source: Courtesy of Kennametal, Inc.

90°100° 80° 60° 55° 35°

Increasing strength

Increased chipping and breaking

FIGURE 8.34 Edge preparations for inserts to improve edge strength. Source: Courtesy of Kennametal, Inc.

Ne

ga

tive

with

la

nd

an

d h

on

e

Ne

ga

tive

with

la

nd

Ne

ga

tive

ho

ne

d

Ne

ga

tive

sh

arp

Po

sitiv

ew

ith

ho

ne

Po

sitiv

esh

arp

Increasing edge strength


Historical Tool Improvement

FIGURE 8.35 Relative time required to machine with various cutting-tool materials, with indication of the year the tool materials were introduced. Note that, within one century, machining time has been reduced by two orders of magnitude. Source: After Sandvik Coromant.

Carbon steel

High-speed steel

Cast cobalt-based alloys

Cemented carbides

Improved carbide grades

First coated grades

First double-coated grades

First triple-coated grades

1900 !10 !20 !30 !40 !50 !60 !70 !80 !90

100

26

15

6

3

1.5

10.7

Ma

ch

inin

g t

ime

(m

in)

Year

!00

0.5 Functionally graded triple-coated


Coated Tools

FIGURE 8.36 Wear patterns on high-speed-steel uncoated and titanium-nitride-coated cutting tools. Note that flank wear is lower for the coated tool.

TiN coated

Uncoated

Flank wear

Rake

face

Tool

FIGURE 8.37 Multiphase coatings on a tungsten-carbide substrate. Three alternating layers of aluminum oxide are separated by very thin layers of titanium nitride. Inserts with as many as 13 layers of coatings have been made. Coating thicknesses are typically in the range of 2 to 10 µm. Source: Courtesy of Kennametal, Inc.

TiN

TiN

TiN

TiC + TiN

TiC + TiN

Carbide substrate

Al2O3

Al2O3

Al2O3


Properties of Cutting Tool Materials

FIGURE 8.38 Ranges of properties for various groups of cutting-tool materials. (See also Tables 8.1 through 8.5.)

Hot hard

ness a

nd w

ear

resis

tance

Strength and toughness

Diamond, cubic boron nitride

Aluminum oxide (HIP)

Aluminum oxide + 30% titanium carbide

Silicon nitride

Cermets

Coated carbides

Carbides

HSS

FIGURE 8.39 Construction of polycrystalline cubic-boron-nitride or diamond layer on a tungsten-carbide insert.

Braze

Polycrystalline cubic boron nitride or diamond layer

Carbide substrate

Tungsten-carbide insert


Characteristics of MachiningCommercial tolerances

Process Characteristics (±mm)Turning Turning and facing operations are performed on all types of

materials; requires skilled labor; low production rate, butmedium to high rates can be achieved with turret lathes andautomatic machines, requiring less skilled labor.

Fine: 0.05-0.13Rough: 0.13Skiving: 0.025-0.05

Boring Internal surfaces or profiles, with characteristics similar tothose produced by turning; sti!ness of boring bar is impor-tant to avoid chatter.

0.025

Drilling Round holes of various sizes and depths; requires boring andreaming for improved accuracy; high production rate, laborskill required depends on hole location and accuracy specified.

0.075

Milling Variety of shapes involving contours, flat surfaces, and slots;wide variety of tooling; versatile; low to medium productionrate; requires skilled labor.

0.13-0.25

Planing Flat surfaces and straight contour profiles on large surfaces;suitable for low-quantity production; labor skill required de-pends on part shape.

0.08-0.13

Shaping Flat surfaces and straight contour profiles on relatively smallworkpieces; suitable for low-quantity production; labor skillrequired depends on part shape.

0.05-0.13

Broaching External and internal flat surfaces, slots, and contours withgood surface finish; costly tooling; high production rate; laborskill required depends on part shape.

0.025-0.15

Sawing Straight and contour cuts on flats or structural shapes; notsuitable for hard materials unless the saw has carbide teethor is coated with diamond; low production rate; requires onlylow skilled labor.

0.8

TABLE 8.7 General characteristics of machining processes.


Lathe Operations

FIGURE 8.40 Variety of machining operations that can be performed on a lathe.

Depth

of cut

ToolFeed, f

(a) Straight turning

(g) Cutting with

a form tool

(e) Facing

(b) Taper turning (c) Profiling

(k) Threading

(d) Turning and

external grooving

(f) Face grooving

(h) Boring and

internal grooving

(i) Drilling

(j) Cutting off (l) Knurling

Workpiece


Tool Angles

FIGURE 8.41 Designations and symbols for a right-hand cutting tool. The designation “right hand” means that the tool travels from right to left, as shown in Fig. 8.19.

High-speed steel Carbide insertsMaterial Back Side End Side Side and end Back Side End Side Side and end

rake rake relief relief cutting edge rake rake relief relief cutting edgeAluminum and

magnesium alloys 20 15 12 10 5 0 5 5 5 15Copper alloys 5 10 8 8 5 0 5 5 5 15Steels 10 12 5 5 15 -5 -5 5 5 15Stainless steels 5 8-10 5 5 15 -5-0 -5-5 5 5 15High-temperature 0 10 5 5 15 5 0 5 5 45

alloysRefractory alloys 0 20 5 5 5 0 0 5 5 15Titanium alloys 0 5 5 5 15 -5 -5 5 5 5Cast irons 5 10 5 5 15 -5 -5 5 5 15Thermoplastics 0 0 20-30 15-20 10 0 0 20-30 15-20 10Thermosets 0 0 20-30 15-20 10 0 15 5 5 15

(a) End view (b) Side view

Shank

Flank face

Back rakeangle (BRA)

End reliefangle (ERA)

Wedgeangle

Side rakeangle (RA)

Side reliefangle (SRA)

(c) Top view

Rake face

End cutting-edgeangle (ECEA)

Side cutting-edgeangle (SCEA)

Noseangle

Noseradius

TA B L E 8 . 8 G e n e r a l recommendations for tool angles in turning.


Turning Operations

FIGURE 8.42 (a) Schematic illustration of a turning operation, showing depth of cut, d, and feed, f. Cutting speed is the surface speed of the workpiece at the tool tip. (b) Forces acting on a cutting tool in turning. Fc is the cutting force; Ft is the thrust or feed force (in the direction of feed); and Fr is the radial force that tends to push the tool away from the workpiece being machined. Compare this figure with Fig. 8.11 for a two-dimensional cutting operation.

(a) (b)

d

DoDf

Workpiece

N

Chuck

Tool

Feed, f

ToolFeed, f

N

Fc

Ft Fr


Cutting Speeds for Turning

FIGURE 8.43 The range of applicable cutting speeds and feeds for a variety of cutting-tool materials.

Cubic boron nitride,diamond, andceramics

Cermets

Coatedcarbides

Uncoatedcarbides

3000

2000

1000

500

300

200

Cu

ttin

g s

pe

ed

(ft

/min

)

0.004 0.008 0.012 0.020 0.030

Feed (in./rev)

0.10 0.20 0.30 0.50 0.75

mm/rev

900

600

300

150

100

50

m/m

in

Cutting SpeedWorkpiece Material m/min ft/minAluminum alloys 200-1000 650-3300Cast iron, gray 60-900 200-3000Copper alloys 50-700 160-2300High-temperature alloys 20-400 65-1300Steels 50-500 160-1600Stainless steels 50-300 160-1000Thermoplastics and thermosets 90-240 300-800Titanium alloys 10-100 30-330Tungsten alloys 60-150 200-500Note: (a) The speeds given in this table are for carbides and ce-ramic cutting tools. Speeds for high-speed-steel tools are lowerthan indicated. The higher ranges are for coated carbides and cer-mets. Speeds for diamond tools are significantly higher than anyof the values indicated in the table.(b) Depths of cut, d, are generally in the range of 0.5-12 mm (0.02-0.5 in.).(c) Feeds, f , are generally in the range of 0.15-1 mm/rev (0.006-0.040 in./rev).

TABLE 8.9 Approximate Ranges of Recommended Cutting Speeds for Turning Operations


Lathe

FIGURE 8.44 General view of a typical lathe, showing various major components. Source: Courtesy of Heidenreich & Harbeck.

Spindle speedselector

Headstock assembly

Spindle (with chuck)

Tool post

Compoundrest

Cross slide

Carriage

Ways

Dead center

Tailstock quill

Tailstockassembly

Handwheel

BedFeed selector

Clutch

Chip pan

Apron

Split nut

Clutch

Longitudinal &transverse feedcontrol

Feed rod

Lead screw


CNC Lathe

FIGURE 8.45 (a) A computer-numerical-control lathe, with two turrets; these machines have higher power and spindle speed than other lathes in order to take advantage of advanced cutting tools with enhanced properties; (b) a typical turret equipped with ten cutting tools, some of which are powered.

DrillMultitooth

cutter

Tool forturning

or boring

Reamer

Individualmotors

Drill

Round turret forOD operationsCNC unit Chuck

End turret for ID operations Tailstock

(a) (b)


Typical CNC Parts

FIGURE 8.46 Typical parts made on computer-numerical-control machine tools.

(a) Housing base

Material: Titanium alloyNumber of tools: 7Total machining time(two operations):5.25 minutes

Material: 52100 alloy steelNumber of tools: 4Total machining time(two operations):6.32 minutes

(c) Tube reducer

Material: 1020 Carbon SteelNumber of tools: 8Total machining time(two operations):5.41 minutes

(b) Inner bearing race

67.4 mm(2.654")

87.9 mm(3.462")

98.4 mm(3.876")

85.7 mm (3.375")32 threads per in.

235.6 mm(9.275")

78.5 mm(3.092")

50.8 mm(2")

23.8 mm(0.938")

53.2 mm(2.094")


Typical Production Rates

Operation RateTurning

Engine lathe Very low to lowTracer lathe Low to mediumTurret lathe Low to mediumComputer-control lathe Low to mediumSingle-spindle chuckers Medium to highMultiple-spindle chuckers High to very high

Boring Very lowDrilling Low to mediumMilling Low to mediumPlaning Very lowGear cutting Low to mediumBroaching Medium to highSawing Very low to lowNote: Production rates indicated are relative: Very low is aboutone or more parts per hour; medium is approximately 100 partsper hour; very high is 1000 or more parts per hour.

TABLE 8.10 Typical production rates for various cutting operations.


Boring Mill

FIGURE 8.47 Schematic illustration of the components of a vertical boring mill.

Cross-rail

Tool head

Workpiece

Work table

Bed

Column


DrillsFIGURE 8.48 Two common types of drills: (a) Chisel-point drill. The function of the pair of margins is to provide a bearing surface for the drill against walls of the hole as it penetrates into the workpiece. Drills with four margins (double-margin) are available for improved drill guidance and accuracy. Drills with chip-breaker features are also available. (b) Crankshaft drills. These drills have good centering ability, and because chips tend to break up easily, they are suitable for producing deep holes.

(a) Chisel-point drill

Tang drive

Shank diameter

Straight shank

Neck

Overall length

Flute length

Body

Point angle

Lip-relief angle

Chisel-edge angle

Chisel edge

Drill diameter

Body diameter clearance

Clearance diameter

(b) Crankshaft-point drill

Lip

Margin

Land

Flutes Helix angle

Shank length

Web

Tang Taper shank

Drilli

ng

Co

re d

rilli

ng

Ste

p d

rilli

ng

Co

un

terb

orin

g

Co

un

ters

inkin

g

Re

am

ing

Ce

nte

r d

rilli

ng

Gu

n d

rilli

ng

High-pressure coolant

FIGURE 8.49 Various types of drills and drilling operations.


Speeds and Feeds in Drilling

Surface Feed, mm/rev (in./rev) Spindle speed (rpm)Speed Drill Diameter Drill Diameter

Workpiece 1.5 mm 12.5 mm 1.5 mm 12.5 mmMaterial m/min ft/min (0.060 in.) (0.5 in.) (0.060 in.) (0.5 in.)Aluminum alloys 30-120 100-400 0.025 (0.001) 0.30 (0.012) 6400-25,000 800-3000Magnesium alloys 45-120 150-400 0.025 (0.001) 0.30 (0.012) 9600-25,000 1100-3000Copper alloys 15-60 50-200 0.025 (0.001) 0.25 (0.010) 3200-12,000 400-1500Steels 20-30 60-100 0.025 (0.001) 0.30 (0.012) 4300-6400 500-800Stainless steels 10-20 40-60 0.025 (0.001) 0.18 (0.007) 2100-4300 250-500Titanium alloys 6-20 20-60 0.010 (0.0004) 0.15 (0.006) 1300-4300 150-500Cast irons 20-60 60-200 0.025 (0.001) 0.30 (0.012) 4300-12,000 500-1500Thermoplastics 30-60 100-200 0.025 (0.001) 0.13 (0.005) 6400-12,000 800-1500Thermosets 20-60 60-200 0.025 (0.001) 0.10 (0.004) 4300-12,000 500-1500Note: As hole depth increases, speeds and feeds should be reduced. Selection of speeds andfeeds also depends on the specific surface finish required.

TABLE 8.11 General recommendations for speeds and feeds in drilling.


Reamers and Taps

FIGURE 8.50 Terminology for a helical reamer.

Chamfer angle Chamfer length

Chamfer relief

Helix angle, -Primary

relief angle

Margin width

Land width

Radial rake

FIGURE 8.51 (a) Terminology for a tap; (b) illustration of tapping of steel nuts in high production.

(b)

Rake angle

Hook angle

(a)

Tap

NutLand

Chamferrelief

Flute

Cutting edge

Heel

Chamferangle


Typical Machined Parts

FIGURE 8.52 Typical parts and shapes produced by the machining processes described in Section 8.10.

(a) (b) (c)

(d) (e) (f)

Drilled and tapped holes

Stepped cavity


Conventional and Climb Milling

(a) (b) (c)

Workpiece

Conventionalmilling

Climbmilling

d

N

D

f

tc

d

v

Cutter

D

v

llc

Workpiece

Cutter

FIGURE 8.53 (a) Illustration showing the difference between conventional milling and climb milling. (b) Slab-milling operation, showing depth of cut, d; feed per tooth, f; chip depth of cut, tc and workpiece speed, v. (c) Schematic illustration of cutter travel distance, lc, to reach full depth of cut.


Face Milling

f

w

v

lc

lc

l

Workpiece

D

Cutter

(b)

f

v

(c)(a)

Insert

(d)

l

d

w

v

Machined surface

Workpiece

Cutter

FIGURE 8.54 Face-milling operation showing (a) action of an insert in face milling; (b) climb milling; (c) conventional milling; (d) dimensions in face milling.

Peripheral relief(radial relief)

Radialrake, 2

Axial rake, 1

End cutting-edge angle

Cornerangle

End relief(axial relief)

FIGURE 8.55 Terminology for a face-milling cutter.


Cutting Mechanics

Insert

Undeformed chip thickness

Depth of cut, d

Leadangle

f

Feed per tooth, f

(a) (b)

FIGURE 8.56 The effect of lead angle on the undeformed chip thickness in face milling. Note that as the lead angle increases, the undeformed chip thickness (and hence the thickness of the chip) decreases, but the length of contact (and hence the width of the chip) increases. Note that the insert must be sufficiently large to accommodate the increase in contact length.

(b)

Exit

Entry

Re-entry

Exit

(a)

Cutter

Workpiece

(c)

Cutter

Desirable

Milledsurface

+ -

Undesirable

FIGURE 8.57 (a) Relative position of the cutter and the insert as it first engages the workpiece in face milling, (b) insert positions at entry and exit near the end of cut, and (c) examples of exit angles of the insert, showing desirable (positive or negative angle) and undesirable (zero angle) positions. In all figures, the cutter spindle is perpendicular to the page.


Milling Operations

(a) Straddle milling (b) Form milling

Arbor

(c) Slotting (d) Slitting

FIGURE 8.58 Cutters for (a) straddle milling; (b) form milling; (c) slotting; and (d) slitting operations.

Cutting SpeedWorkpiece Material m/min ft/minAluminum alloys 300-3000 1000-10,000Cast iron, gray 90-1300 300-4200Copper alloys 90-1000 300-3300High-temperature alloys 30-550 100-1800Steels 60-450 200-1500Stainless steels 90-500 300-1600Thermoplastics and thermosets 90-1400 300-4500Titanium alloys 40-150 130-500Note: (a) These speeds are for carbides, ceramic, cermets, and diamond cuttingtools. Speeds for high-speed-steel tools are lower than those indicated in this table.(b) Depths of cut, d, are generally in the range of 1-8 mm (0.04-0.3 in.).(c) Feeds per tooth, f , are generally in the range of 0.08-0.46 mm/rev (0.003-0.018in./rev).

TABLE 8.12 Approximate range of recommended cutting speeds for milling operations.


Milling Machines

(a) (b)

Work table Head

Column

Base

Workpiece

Saddle

Knee

Overarm

Arbor

Column

Workpiece

Work table

Saddle

Knee

Base

T-slots T-slots

FIGURE 8.59 (a) Schematic illustration of a horizontal-spindle column-and-knee-type milling machine. (b) Schematic illustration of a vertical-spindle column-and-knee-type milling machine. Source: After G. Boothroyd.


Broaching

(a)

(b) (c)

FIGURE 8.60 (a) Typical parts finished by internal broaching. (b) Parts finished by surface broaching. The heavy lines indicate broached surfaces; (c) a vertical broaching machine. Source: (a) and (b) Courtesy of General Broach and Engineering Company, (c) Courtesy of Ty Miles, Inc.


Broaches

(b)

Root radius

Pitch

LandRake orhook angle

Toothdepth

Backoff orclearance angle

(a)

Cut pertooth

Chip gullet

Workpiece

FIGURE 8.61 (a) Cutting action of a broach, showing various features. (b) Terminology for a broach.

Pull end

Root diameter

Follower diameter

Overall length

Shank length

Front pilot

Roughening teeth

Cutting teeth

Semifinishing teeth

Rear pilot

Finishing teeth

FIGURE 8.62 Terminology for a pull-type internal broach, typically used for enlarging long holes.


Saws and Saw Teeth

(a) (b)

Straight tooth

Raker tooth

Wave tooth

Tooth set

Width

Back edge

Tooth spacing

Tooth face

Tooth back (flank)

Tooth back clearance angle

Tooth rake angle (positive)

Gullet depth

FIGURE 8.63 (a) Terminology for saw teeth. (b) Types of saw teeth, staggered to provide clearance for the saw blade to prevent binding during sawing.

M2 HSS 64-66 HRC

Electron-beam weld

(a) (b)

Carbideinsert

Flexible alloy-steelbacking

FIGURE 8.64 (a) High-speed-steel teeth welded on a steel blade. (b) Carbide inserts brazed to blade teeth.


Gear Manufacture

(b)(a)

(c) (d)

Top view

Gearblank

Hob

Gear blank

Hob

Rack-shaped cutter

Gear blank

Gear cutter Base circle

Gear blank

Pitch circle

Pitch circle

Base circle

Gearteeth

Pinion-shaped cutter

Gear blank

Spacer

Cutter spindle

FIGURE 8.65 (a) Schematic illustration of gear generating with a pinion-shaped gear cutter. (b) Schematic illustration of gear generating in a gear shaper, using a pinion-shaped cutter; note that the cutter reciprocates vertically. (c) Gear generating with a rack-shaped cutter. (d) Three views of gear cutting with a hob. Source: After E.P. DeGarmo.


Machining Centers

Tools (cutters)

Index table

Tool storageTool-interchange arm

Traveling column

Spindle

Pallets

Bed

Spindle carrier

Computernumerical-control panel

FIGURE 8.67 Schematic illustration of a computer numerical-controlled turning center. Note that the machine has two spindle heads and three turret heads, making the machine tool very flexible in its capabilities. Source: Courtesy of Hitachi Seiki Co., Ltd.

1st Spindle head

2nd Turret head

1st Turret head

2nd Spindle head

3rd Turret head

FIGURE 8.66 A horizontal-spindle machining center, equipped with an automatic tool changer. Tool magazines in such machines can store as many as 200 cutting tools, each with its own holder. Source: Courtesy of Cincinnati Machine.


Reconfigurable Machines

Magazine unit

Arm unit

Rotational motion

Arm unitBase unitBed unit

Linear motionLinear motion

Functional unit

Rotationalmotion

FIGURE 8.68 Schematic illustration of a reconfigurable modular machining center, capable of accommodating workpieces of different shapes and sizes, and requiring different machining operations on their various surfaces. Source: After Y. Koren.


Reconfigurable Machining Center

(a) (b) (c)

FIGURE 8.69 Schematic illustration of assembly of different components of a reconfigurable machining center. Source: After Y. Koren.


Machining of Bearing Races

1. Finish turning of outside diameter

2. Boring and grooving on outside diameter

3. Internal grooving with a radius-form tool

4. Finish boring of internal groove and rough boring of internal diameter

5. Internal grooving with form tool and chamfering

6. Cutting off finished part; inclined bar picks up bearing race

Tube

Bearingrace

Formtool

Form tool

FIGURE 8.70 Sequences involved in machining outer bearing races on a turning center.


Hexapod

(a) (b)

Spindle

Hexapodlegs

Cutting tool

Workpiece

FIGURE 8.71 (a) A hexapod machine tool, showing its major components. (b) Closeup view of the cutting tool and its head in a hexapod machining center. Source: National Institute of Standards and Technology.


Chatter & Vibration

FIGURE 8.72 Chatter marks (right of center of photograph) on the surface of a turned part. Source: Courtesy of General Electric Company.

1.2

0.8

0.4

0.0

-0.4

-0.8

-1.2

-1.6

-2.00 1000 2000 3000 4000

10-5 s

10-1

V

Cast iron

(a)

1.2

0.8

0.4

0.0

20.4

20.8

21.2

21.6

22.00 1000 2000 3000 4000

10-5 s

10-1

V

Epoxy/graphite

(b)

FIGURE 8.73 Relative damping capacity of (a) gray cast iron and (b) epoxy-granite composite material. The vertical scale is the amplitude of vibration and the horizontal scale is time.

Incre

asin

g d

am

pin

g

Bed only

Bed +carriage

Bed +headstock

Bed +carriage +headstock

Complete machine

FIGURE 8.74 Damping of vibrations as a function of the number of components on a lathe. Joints dissipate energy; thus, the greater the number of joints, the higher the damping. Source: After J. Peters.


Machining EconomicsTotal cost

Machining cost

Nonproductive cost

Tool-change cost

Tool cost

(a)

Co

st

pe

r p

iece

Cutting speed

Machining time

Total time

Nonproductive time

Tool-changing time

(b)

High-efficiency machining range

Cutting speed

Tim

e p

er

pie

ce

FIGURE 8.75 Qualitative plots showing (a) cost per piece, and (b) time per piece in machining. Note that there is an optimum cutting speed for both cost and time, respectively. The range between the two optimum speeds is known as the high-efficiency machining range.


Case Study: Ping Golf Putters

FIGURE 8.76 (a) The Ping Anser® golf putter; (b) CAD model of rough machining of the putter outer surface; (c) rough machining on a vertical machining center; (d) machining of the lettering in a vertical machining center; the operation was paused to take the photo, as normally the cutting zone is flooded with a coolant; Source: Courtesy of Ping Golf, Inc.

(a) Straight turning (b) Cutting of f Common Machining ... · PDF fileManufacturing Processes...

Documents

Transcript of (a) Straight turning (b) Cutting of f Common Machining ... · PDF fileManufacturing Processes...