Common Machining Pr Processes ocesses Tool (a) Straight turning
Tool (b) Cutting off
Cutter End mill
(c) Slab milling
(d) End milling
FIGURE 8.1 Some examples of common common machining machining processes.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Orthogonal Cutting t c
Shiny surface Tool face f ace
Rough surface Chip
- +
Tool
Shear plane
Rake angle " t o
V
!
Flank Relief or clearance angle Shear angle
Workpiece (a) t c
Rough surface Chip
Tool face f ace Tool
- +
Primary shear zone
" t o
Rake angle Flank V
Relief or clearance angle Rough surface
(b)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
FIGURE 8.2 Schematic illustration of a two-dimensional 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.
Orthogonal Cutting t c
Shiny surface Tool face f ace
Rough surface Chip
- +
Tool
Shear plane
Rake angle " t o
V
!
Flank Relief or clearance angle Shear angle
Workpiece (a) t c
Rough surface Chip
Tool face f ace Tool
- +
Primary shear zone
" t o
Rake angle Flank V
Relief or clearance angle Rough surface
(b)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
FIGURE 8.2 Schematic illustration of a two-dimensional 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.
Chip Formation Rake angle,
Chip (90 (9 0° -
Tool
+ )
V c
d
( - )
V s
A
Workpiece
(90 (9 0° - )
C
B
Shear plane
V
A
C
( - ) O B
(a)
(b)
FIGURE 8.3 (a) Schematic illustration illustration of the basic mechanism of chip formation in cutting. (b) Velocity diagram in the cutting zone.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Secondary shear zones Tool Chip
Chip Tool
Primary shear Workpiece zone
BUE
Primary shear zone
(a)
(b)
Types of Chips
(c)
Low shear strain High shear strain
(d)
(e)
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. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
FIGURE 8.5 Shiny (burnished) surface on the tool side of a continuous chip produced in turning.
Hardness in Cutting Zone Chip
316 Built-up edge 474 661 588 565 492 588
372
Hardness (HK)
306
331 286
329 325
(b)
289 289
371 418 604 684 432 383 386 656 589 306 281 466 704567 578 261 361 289 327 512639 587 281 704 565 704 410 734770655 341 297 409 544 503 231 377 656
229
308
317 201 266
251
Workpiece 230 (a)
(c)
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. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Chip Breakers Chip breaker Before Chip
Rake face of tool
After Tool
Clamp Chip breaker Tool
Workpiece
(a)
(b)
Rake face
Radius
Positive rake
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.
0 rake °
(c)
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)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
(b)
(c)
(d)
Oblique Cutting z
Tool
Top view
a t
c
y
i
Chip i = 0°
Tool
a
o
Chip i
i = 15°
o
Workpiece i = 30°
Workpiece
x
(a)
(b)
(c)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Right-Hand Cutting Tool
Side-rake angle, + (SR)
k n a h S i s x A
Face Cutting edge Back-rake angle, + (BR) Nose radius Flank
Axis End-cutting edge angle (ECEA)
Side-relief angle
Toolholder Clamp screw Clamp Insert Seat or shim
Side-cutting edge angle (SCEA) Clearance or end-relief angle Axis (a)
(b)
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).
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Cutting Forces Chip
Tool Chip
R
N
F s
V F
F t F c
F s F c
V F t
F n
R
R
Workpiece
Tool
F
N
(a)
Workpiece
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.
(b)
Cutting force F c = R cos (! − ") =
wt o # cos (! − ")
sin $ cos ($ + ! − ")
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Friction coefficient µ = tan ! =
F t + F c tan " F c − F t tan "
Cutting Data TABLE 8.1 Data on orthogonal cutting of 4130 steel.
mm/rev 200
0
0.1
0.2
0.3
= 5°
!
800
◦
150 10°
) b l (
ut (in.-lb/in3 3 µ us uf α φ γ β F c (lb) F t (lb) ×10 ) 25 20.9 2.55 1.46 56 380 224 320 209 111 35 31.6 1.56 1.53 57 254 102 214 112 102 40 35.7 1.32 1.54 57 232 71 195 94 101 45 41.9 1.06 1.83 62 232 68 195 75 120 to = 0.0025 in.; w = 0.475 in.; V = 90 ft/min; tool: high-speed steel.
100
15°
400
t
F
20°
) N (
◦
uf /ut (%) 35 48 52 62
50 25° 30° 0 35° 40°
0
250 0
2200 0.002 0.004 0.006 0.008 0.010 0.012 Feed (in./rev)
TABLE 8.2 Data on orthogonal cutting of 9445 steel. V φ +10 197 17 400 19 642 21.5 1186 25 -10 400 16.5 637 19 1160 22 to = 0.037 in.; w = α
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. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
µ F t ut β F c 3.4 1.05 46 370 273 400 3.1 1.11 48 360 283 390 2.7 0.95 44 329 217 356 2.4 0.81 39 303 168 328 3.9 0.64 33 416 385 450 3.5 0.58 30 384 326 415 3.1 0.51 27 356 263 385 0.25 in.; tool: cemented carbide. γ
us 292 266 249 225 342 312 289
uf 108 124 107 103 108 103 96
uf /ut (%) 27 32 30 31 24 25 25
Shear Force & Normal Force 320
0
mm2 2
1
3
280 = 20° to 40°
240 ) b l (
s
200
320
1
3
280
1200
1200
240 800
160
F
) N (
) b l ( t
200 160
F
120
120 400
80 = 50,000 psi
40 0
0
mm2 2
0
1
2 3 4 5 A s (in2 x 10-3)
80
20° 25 800 30 35 40 400
) N (
40 0 6
(a)
0 0
1
2
3
A s (in2 x
4
5
6
10-3)
(b)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Shear Stress on Tool Face Tool face Sliding
Sticking
Tool
! "
Stresses on tool face Tool tip
Flank 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).
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Shear-Angle Relationships 50 ) . g e d ( #
, e l g n a r a e h S
T i
40
A n l u m i n u m
30 20
E
q . ( E 8 .2 q . 0 ) ( 8 . 2 1 L ea )
) . g e d (
d
C o p p e r
10 0 230
60
#
Mild steel
" = 0
40 20 0
! = 10 µ =0
220 210
0
30
20 10 (! - ")
40
50
30 0.5
50 1
70 (deg.) 2
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.
60 (b)
(a)
Merchant [Eq. (8.20)] ◦
! = 45
+
" 2
Mizuno [Eqs. (8.22)-(8.23]
# −
!
2
!
Shaffer [Eq. (8.21)] ◦
! = 45
+"−#
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
=
=
◦
"
for
" > 15
◦
for
" < 15
15
◦
Specific Energy Specific Energy Material W-s/mm3 hp-min/in3 Aluminum alloys 0.4-1.1 0.15-0.4 Cast irons 1.6-5.5 0.6-2.0 Copper alloys 1.4-3.3 0.5-1.2 High-temperature alloys 3.3-8.5 1.2-3.1 Magnesium alloys 0.4-0.6 0.15-0.2 Nickel alloys 4.9-6.8 1.8-2.5 Refractory alloys 3.8-9.6 1.1-3.5 Stainless steels 3.0-5.2 1.1-1.9 Steels 2.7-9.3 1.0-3.4 Titanium alloys 3.0-4.1 1.1-1.5 At drive motor, corrected for 80% e fficiency; multiply the energy by 1.25 for dull tools. ∗
∗
TABLE 8.3 Approximate Specific-Energ y Requirements in Machining Operations
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
0 0 5 0 0 6
Chip
Temperatures in Cutting
6 0 0 °
0 5 4
0
0.5
1400 7 0 0
0 0 4 0 6 3
6 5 0
) F ° ( 1300
Tool 3 8 0
mm
Temperature ( C)
6 5 6 0
5 0 0 0 0
130 80 30 Workpiece
/ min 0 f t 5 5
e r u t a r 1200 e p m1100 e t e c a 1000 f r u s k n 900 a l F
1.0
1.5
Work material: AISI 52100 Annealed: 188 HB Tool material: K3H carbide
700
V =
600 0 3 0
Feed: 0.0055 in./rev (0.14 mm/rev)
200
C °
500
800
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.
T
=
1.2Y f
!c
3
V t o K
400 700
0
1100
) 2000 F ° ( e 1800 c a f r e t n 1600 i p i h 1400 c l o o t t 1200 a e r u 1000 t a r e p 800 m e t l a 600 c o L
n
i
m
900
/
t
f
3 0
0 5 5
0
700 2 0
C °
0
500
300
400 0
.008 .016 .024 .032 .040 .048 .056 Distance from tool tip (in.)
0.2 0.4 0.6 0.8 1.0 Fraction of tool-chip contact length measured in the direction of chip flow
(a)
(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.
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. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
) % ( y g r e n E
l T o o
W
c e
p i e
k o r
Chip
Terminology in Turning Feed (mm/rev or in./rev)
Depth of cut (mm or in.)
Chip Tool
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Flank wear
Rake face Rake face
Crater wear depth (KT)
Tool
Flank wear
R
Flank face
Depth-of-cut line
Crater wear
Tool Wear
VBmax VB
Nose radius
Flank face
Depth-of-cut line (a)
Taylor tool life equation: Rake face
Rake face
Flank wear
Crater wear
n
V T
=
C
Flank face
Flank face
(b)
(c)
BUE
Thermal cracking
Flank face Rake face
TABLE 8.4 Range of n values for various cutting tools. (d)
(e)
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. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
High-speed steels Cast alloys Carbides Ceramics
0.08-0.2 0.1-0.15 0.2-0.5 0.5-0.7
Effect of Workpiece on Tool Life 120 ) n i m ( e f i l l o o T
m/min 100 150 200 250
50 a
80
100
b c
) n i m (
40
300 500 700 900 Cutting speed (ft/min)
Hardness (HB) a. b. c. d. e.
As cast As cast As cast Annealed Annealed
0.2
0.1
0.4
e d
0 100
m/s 0.3
265 215 207 183 170
e f i l l o o T
P e a r li t e
80
- f e
M
60
r
r
i t e
a
r
t e
n s i t
40
S
p h e r
o
i c
i d i z e
d
20 Ferrite 20% 40 60 97 100
Pearlite 80% 60 40 3 _
(a)
0 20
30
40 50 60 70 80 Cutting speed (ft/min)
90
(b)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Tool-Life Curves m/min 300
50
300
3000
100 60 40 ) n 20 i
100 ) n i m (
e 20 f i l l 10 o o T
5
400 200
H gi h -s p e e d s t e e l
C a s t a l l o y
m ( e f i l l o o T
C e r C a a m i r c b i d e
°C 1000
1200 1400
Feed constant, speed variable Speed constant, feed variable
10 6 4 2 1
n
0.6 0.2
1 100
800
300 1000 5000 10,000 Cutting speed (ft/min)
(a)
1500 1800 2100 2400 Temperature (°F)
Work material: Heat-resistant alloy Tool material: Tungsten carbide Tool life criterion: 0.024 in. (0.6 mm) flank wear (b)
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. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
e ) t 6 a r 0 20 r 1 a x e n w i r m10 e / t 3 a n r i ( 0 C
°C 700 900
500 a
b
c
Tool Wear
1100 0.30 0.15
n i m /
3
m m
0 800 1200 1600 2000 Average tool-chip interface temperature (°F)
Rake face
FIGURE 8.23 Relationship between craterwear 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.
TABLE 8.5 Allowable average wear lands for cutting tools in various operations. Allowable Wear Land (mm) Operation High-Speed Steels Carbides Turning 1.5 0.4 Face milling 1.5 0.4 End milling 0.3 0.3 Drilling 0.4 0.4 Reaming 0.15 0.15 Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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 mm r a1.5 e w k n1.0 a l f n0.5 a e M
0
in.
in.
0.050 0.040 0.030 0.020 0.010 0
a r
w e t e r C r a
r e a
k w F l a n
0.005 0.004 0.003 0.002 0.001 0
mm h t p
e 0.15 d
0.1 0.05 0
r e t a r c m u m i x a M
) V m1500 ( S M R n a 1000 e M
500 0
10
50 20 30 40 Elapsed machining time (min)
60
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Roughness (R a) µm 50 µ in. 2000
Process
25 1000
12.5 500
6.3 2 50
3.2 1 25
1.6 63
0.8 32
0.40 16
0.20 8
0.10 4
0.05 2
0.025 0.012 1 0.5
Rough cutting Flame cutting
Average application
Snagging (coarse grinding)
Less frequent application
Surface Finish
Sawing Casting Sand casting Permanent mold casting Investment casting Die casting Forming Hot rolling Forging Extruding Cold rolling, drawing Roller burnishing Machining Planing, shaping Milling Broaching Reaming Turning, boring Drilling Advanced machining Chemical machining Electrical-discharge machining Electron-beam machining Laser machining Electrochemical machining Finishing processes Honing Barrel finishing Electrochemical grinding Grinding Electropolishing Polishing Lapping Superfinishing
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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).
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)
h t p e d
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
g n i s a t e u r c c f n I o
Tool
Workpiece
Machined surface
Inclusions in Free-Machining Steels
(a)
(b)
(c)
FIGURE 8.29 Photomicrographs showing various types of inclusions in low-carbon, resulfurized freemachining 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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Hardness of Cutting Tools °
100
95
C
300
500
700
C e ra m i c s
90 70
C a r bi d e s
85
65 60
) A 80 R H ( s s 75 e n d r a H 70
C
C a s
a r b o
55
t a
n
t o
l l o y s
o
l
H i g h - s p e e d s t e e l s
s t e e l s
65 60
50 45 40 35 30 25 20
55 0
200
400
C R H
600 800 1000 1200 1400 Temperature ( F) °
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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.
Tool Materials TABLE 8.6 Typical range of properties of various tool materials. Carbides High-Speed Steel 83-86 HRA
Cast Alloys 82-84 HRA
Cubic Boron Nitride 4000-5000 HK
Property WC TiC Ceramics Hardness 90-95 HRA 91-93 HRA 91-95 HRA Compressive strength MPa 4100-4500 1500-2300 4100-5850 3100-3850 2750-4500 6900 psi ×103 600-650 220-335 600-850 450-560 400-650 1000 Transverse rupture strength MPa 2400-4800 1380-2050 1050-2600 1380-1900 345-950 700 psi ×103 350-700 200-300 150-375 200-275 50-135 105-200 Impact strength J 1.35-8 0.34-1.25 0.34-1.35 0.79-1.24 < 0.1 < 0.5 in.-lb 12-70 3-11 3-12 7-11 < 1 < 5 Modulus of elasticity GPa 200 — 520-690 310-450 310-410 850 psi ×106 30 — 75-100 45-65 45-60 125 Density kg/m3 8600 8000-8700 10,000-15,000 5500-5800 4000-4500 3500 lb/in3 0.31 0.29-0.31 0.36-0.54 0.2-0.22 0.14-0.16 0.13 Volume of hard phase (%) 7-15 10-20 70-90 — 100 95 Melting or decomposition temperature C 1300 — 1400 1400 2000 1300 F 2370 — 2550 2550 3600 2400 Thermal conductivity, W/mK 30-50 — 42-125 17 29 13 Coefficient of thermal expansion, ×10 6 / C 12 — 4-6.5 7.5-9 6-8.5 4.8 The values for polycrystalline diamond are generally lower, except impact strength, which is higher. ◦ ◦
−
◦
∗
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Single Crystal Diamond 7000-8000 HK ∗
6900 1000
1350
< 0.2 < 2 820-1050 120-150 3500 0.13 95
700 1300 500-2000 1.5-4.8
Properties of Tungsten-Carbide Tools 600 e s r e v s ) 500 n 2 a r m t m d / n g 400 a k e ( h v t i s g 300 s n e e r t p r m s 200 o e c r u t , ) p g u m r 100 ( r a e 0 W 0
HRA 92.4 1750 C o m
p r
H a r d n
e s s
e s s
r e u p t u e - r
i v e
s t r e n
gt h
t h
g s t r e n
e r s s v a n r T
a r W e
5
10 15 20 25 Cobalt content (% by weight)
90.5 1500 ) V H ( 88.5 1250 s s e n d 85.7 1000 r a h s r e k 750 i c V 500 30
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)].
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Inserts Toolholder Clamp screw
Shank
Insert Lockpin Seat
Clamp Insert Seat or shim (a)
(b)
(c)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Insert Strength Increasing strength 100°
90°
80°
60°
55°
35°
Increased chipping and breaking
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. e d e v n n i t l a o a h g h e t i d n N w a
e d v n i t l a a g h t e i N w
e v d i t e a n g o e h N
e v i t p r a a g h e s N
e e n v o i t i h s o h t i P w
e v p i r t i a s h o s P
Increasing edge strength
FIGURE 8.34 Edge preparations for inserts to improve edge strength. Source: Courtesy of Kennametal, Inc. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Historical Tool Improvement 100
) n i m ( e m i t g n i n i h c a M
Carbon steel
26
High-speed steel Cast cobalt-based alloys
15
Cemented carbides
6
Improved carbide grades
3
First coated grades First double-coated grades First triple-coated grades
1.5 1 0.7 0.5
Functionally graded triple-coated
1900 10 20 30 40 50 60 70 80 90 00 !
!
!
!
!
!
!
!
!
!
Year
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Coated Tools TiN
Rake face
TiC
Tool
+ TiN
Al2O3 TiN Al2O3
TiN coated
TiN Al2O3
Uncoated
TiC
+ TiN
Carbide substrate
Flank wear
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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.
Properties of Cutting Tool Materials Diamond, cubic boron nitride e c n a t s i s e r r a e w d n a s s e n d r a h t o H
Aluminum oxide (HIP) Aluminum oxide + 30% titanium carbide Silicon nitride Cermets Coated carbides Carbides
HSS
Strength and toughness
FIGURE 8.38 Ranges of properties for various groups of cutting-tool materials. (See also Tables 8.1 through 8.5.) Tungsten-carbide insert Braze
Polycrystalline cubic boron nitride or diamond layer Carbide substrate
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
FIGURE 8.39 Construction of polycrystalline cubicboron-nitride or diamond layer on a tungsten-carbide insert.
Characteristics of Machining Process Turning
Boring
Drilling
Milling
Planing
Shaping
Broaching
Sawing
Characteristics Turning and facing operations are performed on all types of materials; requires skilled labor; low production rate, but medium to high rates can be achieved with turret lathes and automatic machines, requiring less skilled labor. Internal surfaces or profiles, with characteristics similar to those produced by turning; stiff ness of boring bar is important to avoid chatter. Round holes of various sizes and depths; requires boring and reaming for improved accuracy; high production rate, labor skill required depends on hole location and accuracy specified. Variety of shapes involving contours, flat surfaces, and slots; wide variety of tooling; versatile; low to medium production rate; requires skilled labor. Flat surfaces and straight contour profiles on large surfaces; suitable for low-quantity production; labor skill required depends on part shape. Flat surfaces and straight contour profiles on relatively small workpieces; suitable for low-quantity production; labor skill required depends on part shape. External and internal flat surfaces, slots, and contours with good surface finish; costly tooling; high production rate; labor skill required depends on part shape. Straight and contour cuts on flats or structural shapes; not suitable for hard materials unless the saw has carbide teeth or is coated with diamond; low production rate; requires only low skilled labor.
TABLE 8.7 General characteristics of machining processes. Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Commercial tolerances (±mm) Fine: 0.05-0.13 Rough: 0.13 Skiving: 0.025-0.05 0.025
0.075
0.13-0.25
0.08-0.13
0.05-0.13
0.025-0.15
0.8
Depth of cut
Lathe Operations
Tool
Feed, f
(a) Straight turning
(b) Taper turning
(c) Profiling
(d) Turning and external grooving
(e) Facing
(f) Face grooving
(g) Cutting with a form tool
(h) Boring and internal grooving
(i) Drilling
Workpiece
(j) Cutting off
(k) Threading
(l) Knurling
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
FIGURE 8.40 Variety of machining operations that can be performed on a lathe.
Tool Angles Side rake angle (RA)
Back rake angle (BRA)
Wedge angle
Side relief angle (SRA) (a) End view
End cutting-edge angle (ECEA)
Shank
Flank face
End relief angle (ERA)
Nose radius
Nose angle
Side cutting-edge angle (SCEA)
(b) Side view
(c) Top view
Material
TABL E 8. 8 Ge ne ra l recommendations for tool angles in turning.
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.
Rake face
High-speed steel End Side Side and end relief relief cutting edge
Back rake
Side rake
20 5 10 5 0
15 10 12 8-10 10
12 8 5 5 5
10 8 5 5 5
0 0 5 0 0
20 5 10 0 0
5 5 5 20-30 20-30
5 5 5 15-20 15-20
Aluminum and magnesium alloys Copper alloys Steels Stainless steels High-temperature alloys Refractory alloys Titanium alloys Cast irons Thermoplastics Thermosets
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Carbide inserts End Side Side and end relief relief cutting edge
Back rake
Side rake
5 5 15 15 15
0 0 -5 -5-0 5
5 5 -5 -5-5 0
5 5 5 5 5
5 5 5 5 5
15 15 15 15 45
5 15 15 10 10
0 -5 -5 0 0
0 -5 -5 0 15
5 5 5 20-30 5
5 5 5 15-20 5
15 5 15 10 15
Turning Operations
N
N F c
Workpiece F t
d
Df
Chuck
Tool
F r
Do
Feed, f
Tool
Feed, f (a)
(b)
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. F c is the cutting force; F t is the thrust or feed force (in the direction of feed); and F r 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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Cutting Speeds for Turning 0.10
mm/rev 0.20 0.30
3000
0.50
0.75
900 Cubic boron nitride, diamond, and 600 ceramics
2000 ) n i m / t f ( 1000 d e e p s g n i t t 500 u C
Cermets
300
Coated carbides
n i m / m
150
Uncoated carbides
100
300
200 0.004
0.008 0.012 Feed (in./rev)
0.020 0.030
50
FIGURE 8.43 The range of applicable cutting speeds and feeds for a variety of cutting-tool materials.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Cutting Speed Workpiece Material m/min ft/min Aluminum alloys 200-1000 650-3300 Cast iron, gray 60-900 200-3000 Copper alloys 50-700 160-2300 High-temperature alloys 20-400 65-1300 Steels 50-500 160-1600 Stainless steels 50-300 160-1000 Thermoplastics and thermosets 90-240 300-800 Titanium alloys 10-100 30-330 Tungsten alloys 60-150 200-500 Note: (a) The speeds given in this table are for carbides and ceramic cutting tools. Speeds for high-speed-steel tools are lower than indicated. The higher ranges are for coated carbides and cermets. Speeds for diamond tools are significantly higher than any of the values indicated in the table. (b) Depths of cut, d , are generally in the range of 0.5-12 mm (0.020.5 in.). (c) Feeds, f , are generally in the range of 0.15-1 mm/rev (0.0060.040 in./rev).
TABLE 8.9 Approximate Ranges of Recommended Cutting Speeds for Turning Operations
Lathe Tool post
Compound rest
Spindle (with chuck) Headstock assembly Spindle speed selector Cross slide Clutch Feed selector Apron
Carriage
Dead center Tailstock quill
Ways
Tailstock assembly Handwheel Longitudinal & transverse feed control Bed Lead screw
Split nut Feed rod Chip pan
Clutch
FIGURE 8.44 General view of a typical lathe, showing various major components. Source: Courtesy of Heidenreich & Harbeck.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
CNC Lathe CNC unit
Chuck
Round turret for OD operations
Drill
Multitooth cutter
Tool for turning or boring
Reamer Individual motors Drill End turret for ID operations
Tailstock (a)
(b)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Typical CNC Parts
67.4 mm (2.654")
87.9 mm (3.462") 98.4 mm (3.876")
235.6 mm (9.275")
50.8 mm (2")
23.8 mm (0.938")
53.2 mm (2.094")
85.7 mm (3.375") 32 threads per in. 78.5 mm (3.092") Material: Titanium alloy Number of tools: 7 Total machining time (two operations): 5.25 minutes
Material: 52100 alloy steel Number of tools: 4 Total machining time (two operations): 6.32 minutes
Material: 1020 Carbon Steel Number of tools: 8 Total machining time (two operations): 5.41 minutes
(a) Housing base
(b) Inner bearing race
(c) Tube reducer
FIGURE 8.46 Typical parts made on computer-numerical-control machine tools.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Typical Production Rates Operation Rate Turning Engine lathe Very low to low Tracer lathe Low to medium Turret lathe Low to medium Computer-control lathe Low to medium Single-spindle chuckers Medium to high Multiple-spindle chuckers High to very high Boring Very low Drilling Low to medium Milling Low to medium Planing Very low Gear cutting Low to medium Broaching Medium to high Sawing Very low to low Note: Production rates indicated are relative: Very low is about one or more parts per hour; medium is approximately 100 parts per hour; very high is 1000 or more parts per hour.
TABLE 8.10 Typical production rates for various cutting operations.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Boring Mill Cross-rail
Tool head Workpiece Work table Bed Column
FIGURE 8.47 Schematic illustration of the components of a vertical boring mill.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Drills Tang
Point angle
Taper shank
FIGURE 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.
Drill diameter Tang drive
Body diameter clearance Flutes Helix angle
Lip-relief angle
Clearance diameter
Chisel-edge angle
Neck Shank diameter
Web
Straight shank Shank length
Chisel edge Flute length Body
Margin Lip
d n a L
Overall length (a) Chisel-point drill
(b) Crankshaft-point drill
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
g n i l l i r D
g n i l l i r d e r o C
g n i l l i r d p e t S
g n i r o b r e t n u o C
g n i k n i s r e t n u o C
g n i m a e R
g n i l l i r d r e t n e C
g n i l l i r d n u G
High-pressure coolant
FIGURE 8.49 Various types of drills and drilling operations.
Speeds and Feeds in Drilling Surface Speed
Feed, mm/rev (in./rev) Spindle speed (rpm) Drill Diameter Drill Diameter Workpiece 1.5 mm 12.5 mm 1.5 mm 12.5 mm Material 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) 6400-25,000 800-3000 Magnesium alloys 45-120 150-400 0.025 (0.001) 0.30 (0.012) 9600-25,000 1100-3000 Copper alloys 15-60 50-200 0.025 (0.001) 0.25 (0.010) 3200-12,000 400-1500 Steels 20-30 60-100 0.025 (0.001) 0.30 (0.012) 4300-6400 500-800 Stainless steels 10-20 40-60 0.025 (0.001) 0.18 (0.007) 2100-4300 250-500 Titanium alloys 6-20 20-60 0.010 (0.0004) 0.15 (0.006) 1300-4300 150-500 Cast irons 20-60 60-200 0.025 (0.001) 0.30 (0.012) 4300-12,000 500-1500 Thermoplastics 30-60 100-200 0.025 (0.001) 0.13 (0.005) 6400-12,000 800-1500 Thermosets 20-60 60-200 0.025 (0.001) 0.10 (0.004) 4300-12,000 500-1500 Note: As hole depth increases, speeds and feeds should be reduced. Selection of speeds and feeds also depends on the specific surface finish required. TABLE 8.11 General recommendations for speeds and feeds in drilling.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Reamers and Taps Radial rake
Chamfer length Chamfer angle
Margin width Chamfer relief Land width
FIGURE 8.50 Terminology for a helical reamer.
Helix angle, Primary relief angle
Chamfer relief
Chamfer angle
Tap
Land
FIGURE 8.51 (a) Terminology for a tap; (b) illustration of tapping of steel nuts in high production.
Nut Rake angle
Heel
Flute
Cutting edge
Hook angle (a)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
(b)
Typical Machined Parts
(a)
(b)
(c) Stepped cavity
(d)
(e)
Drilled and tapped holes
(f)
FIGURE 8.52 Typical parts and shapes produced by the machining processes described in Section 8.10.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Conventional and Climb Milling D
D
Cutter t c
d
Cutter
N
d v
f
Workpiece
v
(a)
l
l c
Workpiece Conventional Climb milling milling (b)
(c)
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, l c, to reach full depth of cut.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Face Milling l c
Insert
f
f
Workpiece
Workpiece
v
l
v v
D
w
l d
Cutter
Cutter
w
Machined surface
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.
l c
(a)
(b)
(c)
(d)
Peripheral relief (radial relief)
End cutting-edge angle
Axial rake, 1
FIGURE 8.55 Terminology erminolog y for a facemilling cutter.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
End relief (axial relief)
Corner angle
Radial rake, 2
Cutting Mechanics Lead angle
Insert
FIGURE 8.56 The effect effect of lead angle 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.
Undeformed chip thickness Depth of cut, d f
Feed per tooth, f
(b)
(a)
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 showing desirable (positive or negative angle) and undesirable (zero angle) positions. In all figures, the cutter spindle is perpendicular to the page.
Workpiece
Exit
Re-entry
Entry
-
+
Exit Cutter Milled surface Undesirable
Desirable Cutter (a)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
(b)
(c)
Milling Operations Arbor
(a) Straddle milling
(b) Form milling
(c) Slotting
(d) Slitting
FIGURE 8.58 Cutters for (a) straddle milling; (b) form milling; (c) slotting; and (d) slitting operations.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Cutting Speed Workpiece Material m/min ft/min Aluminum alloys 300-3000 1000-10,000 Cast iron, gray 90-1300 300-4200 Copp er alloys 90-1000 300-3300 High-temperature alloys 30-550 100-1800 Steels 60-450 200-1500 Stainless steels 90-500 300-1600 Thermoplastics and thermosets 90-1400 300-4500 Titanium alloys 40-150 130-500 Note: (a) These speeds are for carbides, ceramic, cermets, and diamond cutting tools. 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 (0.003-0.018 in./rev).
TABLE 8.12 Approximate range of recommended cutting speeds for milling operations.
Milling Machines Head
Work table
Overarm Column Arbor
Work table
Column Workpiece
Saddle
T-slots
Workpiece Saddle T-slots Knee
Knee Base
Base
(a)
(b)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Broaches Rake or hook angle Chip gullet
Land Pitch
Backoff or clearance angle
Tooth depth
Cut per tooth Workpiece (a)
FIGURE 8.61 (a) Cutting action of a broach, showing various features. (b) Terminology for a broach.
Root radius (b)
Semifinishing teeth
Pull end
Front pilot
Roughening teeth
Finishing teeth
Rear pilot Follower diameter
FIGURE 8.62 Terminology for a pull-type internal broach, typically used for enlarging long holes.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Root diameter Shank length
Cutting teeth Overall length
Saws and Saw Teeth Tooth set
Back edge Tooth spacing
Straight tooth Width
Tooth face Tooth back (flank)
Tooth back clearance angle
Gullet depth Tooth rake angle (positive)
Raker tooth
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.
Wave tooth (a)
(b)
M2 HSS 64-66 HRC Carbide insert
Electron-beam weld
FIGURE 8.64 (a) High-speed-steel teeth welded on a steel blade. (b) Carbide inserts brazed to blade teeth.
Flexible alloy-steel backing
(a)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
(b)
Gear cutter Base circle
Pitch circle Cutter spindle Spacer
Gear blank
Pitch circle
Pinion-shaped cutter
Base circle
Gear blank
(a)
Gear Manufacture
Gear teeth
(b)
Top vi ew
Gear blank
Hob
Rack-shaped cutter Hob
Gear blank
Gear blank
(c)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
(d)
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 Tool storage
Tool-interchange arm Traveling column
Tools (cutters)
Spindle Spindle carrier Computer numerical-control panel
Index table
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.
Pallets Bed
1st Turret head 2nd Turret head 1st Spindle head
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
2nd Spindle head 3rd Turret head
Reconfigurable Machines Magazine unit
Rotational motion
Arm unit Functional unit
Rotational motion Linear motion
Linear motion
Bed unit
Base unit
Arm unit
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Machining of Bearing Races Tube
Form tool 1. Finish turning of outside diameter
2. Boring and grooving on outside diameter
3. Internal grooving with a radius-form tool
Form tool
4. Finish boring of internal groove and rough boring of internal diameter
5. Internal grooving with form tool and chamfering
Bearing race 6. Cutting off finished part; inclined bar picks up bearing race
FIGURE 8.70 Sequences involved in machining outer bearing races on a turning center.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Hexapod Hexapod legs
Spindle
Cutting tool Workpiece (a)
(b)
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.
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
Chatter & Vibration V
1 -
0 1
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 -2.0
-
Cast iron 0
1000
Bed + carriage
Bed + headstock
2000 -5
3000
4000
Epoxy/graphite 0
1000
2000
3000
4000
-5
10 s
10 s
(a)
(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.
g n i p m a d g n i s a e r c n I
Bed only
1.2 0.8 0.4 0.0 V 1 20.4 0 1 20.8 21.2 21.6 22.0
Bed + carriage + headstock
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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.
Total cost e c e i p r e p t s o C
Machining Economics
Machining cost Tool-change cost Nonproductive cost Tool cost Cutting speed (a) High-efficiency machining range
e c e i p r e p e m i T
Total time
Machining time Tool-changing time Nonproductive time Cutting speed (b)
Manufacturing Processes for Engineering Materials, 5th ed. Kalpakjian • Schmid © 2008, Pearson Education
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.