CHAPTER 9
MaterialRemoval
Processes:
Abrasive,
Chemical,
Electrical, and
High-energy
Beams
Manufacturing Processes for Engineering Materials, 4th ed.
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Knoop Hardness for Various Materials
Common glass
Flint, quartz
Zirconium oxide
Hardened steels
Tungsten carbide
Aluminum oxide
350-500
800-1100
1000
700-1300
1800-2400
2000-3000
Titanium nitride
Titanium carbide
Silicon carbide
Boron carbide
Cubic boron nitride
Diamond
TABLE 9.1 Knoop hardness range for various materials and abrasives.
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2000
1800-3200
2100-3000
2800
4000-5000
7000-8000
Physical Model of a Grinding Wheel
FIGURE 9.1 Schematic illustration of a physical model of a grinding wheel, showing its
structure and wear and fracture patterns.
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Common Types of Grinding Wheels
FIGURE 9.2 Some
common types of
grinding wheels made
with conventional
abrasives. Note that each
wheel has a specific
grinding face. Grinding
on other surfaces is
improper and unsafe.
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Superabrasive-Wheel Configurations
FIGURE 9.3 Examples of superabrasive-wheel configurations. The annular regions (rim)
are superabrasive grinding surfaces, and the wheel itself (core) is generally made of metal or
composites. Note that the basic numbering of wheel type is the same as shown in Fig. 9.2.
The bonding materials for the superabrasives are (a), (d) and (e) resinoid, metal,or vitrified;
(b) metal; (c) vitrified; and (f) resinoid.
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Standard Marking System For AluminumOxide Abrasives
FIGURE 9.4a Standard marking system for aluminum-oxide and silicon-carbide bonded
abrasives.
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Standard Marking System for Diamond
Abrasives
FIGURE 9.4b Standard marking system for diamond and cubic-boron-nitride bonded
abrasives.
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Grinding and Chip Production
FIGURE 9.5 The grinding surface of an abrasive
wheel (A46-J8V), showing grains, porosity, wear
flats on grains (see also Fig. 9.8), and metal chips
from the workpiece adhering to the grains. Note
the random distribution and shape of the abrasive
grains. Magnification: 50X
FIGURE 9.6 Grinding chip being produced by a
single abrasive grain: (A) chip, (B) workpiece, (C)
abrasive grain. Note the large negative rake angle of
the grain. The inscribed circle is 0.065 mm (0.0025 in.)
in diameter. Source: M. E. Merchant.
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Variables in Surface Grinding
PROCESS VARIABLE
Wheel speed (m/min)
Work speed (m/min)
Feed (mm/pass)
CONVENTIONAL
GRINDING
1500-3000
10-60
0.01-0.05
CREEP-FEED
GRINDING
1500-3000
0.1-1
1-6
BUFFING
POLISHING
1800-3600
-
1500-2400
-
TABLE 9.2 Typical ranges of speeds and feeds for abrasive processes.
FIGURE 9.7 Variables in surface
grinding. In actual grinding, the
wheel depth of cut d, and contact
length, l, are much smaller than the
wheel diameter, D. The dimension t
is called the grain depth of cut.
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Chip Formation
FIGURE 9.8 Chip formation and
plowing of the workpiece surface by an
abrasive grain.
FIGURE 9.9 Schematic illustration of
chip formation by an abrasive grain. Note
the negative rake angle, the small shear
angle, and the wear flat on the grain.
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Energy in Abrasive Machining
WORKPIECE MATERIAL
Aluminum
Cast iron (class 40)
Low-carbon steel (1020)
Titanium alloy
Tool steel (T15)
HARDNESS
150 HB
215 HB
110 HB
300 HB
67 HRC
SPECIFI C ENERGY
3
3
W-s/mm
hp-min/in.
7-27
2.5-10
12-60
4.5-22
14-68
5-25
16-55
6-20
18-82
6.5-30
TABLE 9.3 Approximate specific energy requirements for surface grinding.
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Residual Stresses on Workpiece Surface
FIGURE 9.10 Residual stresses developed on the workpiece surface in grinding of
tungsten: (a) effect of wheel speed and (b) effect of grinding fluid. Tensile residual stresses
on a surface controlled to minimize residual stresses. This process is known as low-stress
grinding. Source: After N. Zlatin et al., 1963.
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Wheel Dressing
FIGURE 9.11 Shaping the grinding face of a wheel by dressing it with computer controlled
shaping features. Note that the diamond dressing tool is normal to the surface at point of
contact. Source: Okuma Machinery Works Ltd.
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Surface-Grinding Operations
FIGURE 9.12 Schematic illustration of surface-grinding operations. (a) Traverse grinding
with a horizontal-spindle surface grinder. (b) Plunge grinding with a horizontal-spindle
surface grinder, producing a groove in the workpiece. (c) Vertical-spindle rotary-table
grinder (also known as the Blanchard-type grinder).
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Horizontal-Spindle Surface Grinder
FIGURE 9.13 Schematic illustration of a horizontal-spindle surface grinder. The majority
of grinding operations are done on such machines.
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Traverse and Plunge Grinding of Threads
FIGURE 9.14 Thread grinding by (a) traverse and (b) plunge grinding.
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Internal-Grinding Operations
FIGURE 9.15 Schematic illustrations of internal-grinding operations.
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Centerless-Grinding Operations
FIGURE 9.16 Schematic illustration of centerless-grinding operations.
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Computer-Numerical-Control Centerless
Grinding Machine
FIGURE 9.17 A
computer-numericalcontrol centerless
grinding machine. The
movement of the
workpiece is
perpendicular to the
page. Source: Coutesy of
Cincinnati Milacron, Inc.
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Creep-Feed Grinding Process
FIGURE 9.18 (a) Schematic illustration of the creep-feed grinding process. Note the large
wheel depth of cut. (b) A shaped groove produced on a flat surface in one pass by creep-feed
grinding. Groove depth can be on the order of a few mm. (c) An example of creep-feed
grinding with a shaped wheel. Source: Courtesy of Blohm, Inc., and Manufacturing
Engineering, Society of Manufacturing Engineers. See also Fig. 9.30.
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Ultrasonic-Machining Process
FIGURE 9.19 (a) Schematic illustration of the ultrasonic-machining process by which
material is process by which material is removed through microchipping and erosion. (b)
and (c) typical examples of holes produced by ultrasonic machining. Note the dimensions
of cut and the types of workpiece materials.
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Structure of a Coated Abrasive
FIGURE 9.20 Schematic illustration of the structure of a coated abrasive. Sandpaper,
developed in the 16th century, and emery cloth are common examples of coated abrasives.
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Honing Tool
FIGURE 9.21 Schematic illustration of a honing tool to improve the surface finish of bored
or ground holes.
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Superfinishing of a Cylindrical Part
FIGURE 9.22 Schematic illustration of the superfinishing process for a cylindrical part: (a)
cylindrical microhoning; (b) centerless microhoning.
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Lapping Process
FIGURE 9.23 (a) Schematic illustration of the lapping process. (b) Production lapping on
flat surfaces. (c) Production lapping on cylindrical surfaces.
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Magnetic Fields Used to Polish Balls and
Rollers
FIGURE 9.24 Schematic illustration of the use of magnetic fields to polish balls and
rollers: (a) magnetic float polishing of ceramic balls; (b)magnetic-field-assisted polishing of
rollers . Source: R. Komanduri, M. Doc, and M. Fox.
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Characteristics of Abrasive Machining
PROCESS
CHARACTERISTI CS
Chemical machining
(CM)
Shallow remova l (up to 12 mm) on
large flat or curved surfaces;
blanking of thin sheets; low tooling
and equipment cost; suitable for low
production runs.
Complex shapes with deep cavities;
highest rate of material removal;
expensive tooling and equipment;
high power consumption; medium to
high production quantity.
Cutting off and sharpening hard
materials, such as tungsten-carbide
tools; also used as a honing
process; higher material remova l
rate than grinding.
Shaping and cutting complex parts
made of hard materials; some
surface damage may result; also
used for grinding and cutting;
versatile; expensive tooling and
equipment.
Contour cutting of flat or curved
surfaces; expensive equipment.
Electrochemical
machining (ECM)
Electrochemical grinding
(ECG)
Electrical-discharge
machining (EDM)
Wire EDM
PROCESS PARAMETE RS
AND TY PICAL MATERIAL
REMOVAL RATE OR
CUTT ING SPEED
0.025-0.1 mm/min.
2
V: 5-25 dc; A: 1.5-8 A/mm ;
2.5-12 mm/min, depending on
current density.
2
A: 1-3 A/mm ; Typically 1500
3
mm /min per 1000 A.
V: 50-380; A: 0.1-500;
3
Typically 300 mm /min.
Varies with workpiece material
and its thickness.
TABLE 9.4 General characteristics of abrasive machining operations.
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Characteristics of Abrasive Machining (cont.)
PROCESS
CHARACTERISTI CS
Laser-beam machining
(LBM)
Cutting and holemaking on thin
materials; heat-affected zone; does
not require a vacuum; expensive ;
equipment; consumes much energy;
extreme caution required in use.
Cutting and holemaking on thin
materials; very small holes and
slots; heat-affected zone; requ ires a
vacuum; expensive equipment.
Cutting all types of nonmetallic
materials to 25 mm (1 in.) and
greater in thickness; suitable for
contour cutting of flexible materials;
no thermal damage; environmentally
safe process.
Single or multilayer cutting of
metallic and nonmetallic materials.
Cutting, slotting, deburring, flash
remova l, etching, and cleaning of
metallic and nonmetallic materials;
tends to round off sharp edges;
some hazard because of airborne
particulates.
Electron-beam
machining (EBM)
Water-jet machining
(WJM)
Abrasive water-jet
machining (AWJM)
Abrasive -jet machining
(AJM)
PROCESS PARAMETE RS
AND TY PICAL MATERIAL
REMOVAL RATE OR
CUTT ING SPEED
0.50-7.5 m/min.
3
1-2 mm /min.
Varies considerably with
workpiece material.
Up to 7.5 m/min.
Varies considerably with
workpiece material.
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Chemical Milling
FIGURE 9.25 (a) Missile skin-panel section contoured by chemical milling to improve the
stiffness-to-weight ratio of the part. (b) Weight reduction of space launch vehicles by
chemical milling of aluminum-alloy plates. These panels are milled after the plates have first
been formed into shape, such as by roll forming or stretch forming. The design of the
chemically machined rib patterns can be modified readily at minimal cost. Source: Advanced
Materials and Processes, ASM International, December 1990, p.43.
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Chemical-Machining Process
FIGURE 9.26 (a) Schematic illustration of the chemical-machining process. Note that no
forces or machine tools are involved in this process. (b) Stages in producing a profiled
cavity by chemical machining.
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Surface Roughness and Tolerances
FIGURE 9.27 Surface
roughness and
tolerances obtained in
various machining
processes. Note the
wide range within each
process. (See also Fig.
8.33.) Source:
Reprinted from
Machining Data
Handbook, 3d. ed.
Copyright © 1980, by
permission of the
institute of Advanced
Manufacturing
Sciences.
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Chemical Blanking
FIGURE 9.28 Various parts made by chemical blanking. Note the fine detail. Source:
Courtesy of Buckabee-Mears St. Paul.
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Electrochemical-Machining
FIGURE 9.29 Schematic
illustration of the
electrochemical-machining
process. This process is the
reverse of electroplating,
described in Section 4.5.1.
FIGURE 9.30 Typical parts made by electrochemical
machining. (a) Turbine blade made of a nickel alloy, 360 HB.
Source: Metal Handbook, 9th ed., Vol. 3, Materials Park, OH:
ASM International, 1980, p. 849. (b) Thin slots on a 4340steel roller-bearing cage. (c) Integral airfoils on a compressor
disk.
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Electrochemical-Grinding Process
FIGURE 9.31 (a) Schematic illustration of the electrochemical-grinding process. (b) Thin
slot produced on a round nickel-alloy tube by this process.
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Electrical-Discharge-Machining Process
FIGURE 9.32 Schematic illustration of the electrical-discharge-machining process.
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Cavities made with electrical-dischargemachining process
FIGURE 9.33 (a) Examples of cavities produced by the electrical-discharge-machining process, using
shaped electrodes. The two round parts (rear) are the set of dies for extruding the aluminum piece shown
in front. Source: Courtesy of AGIE USA Ltd. (b) A spiral cavity produced by a rotating electrode. Source:
American Machinist. (c) Holes in a fuel-injection nozzle made by electrical-discharge machining.
Material: Heat-treated steel.
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Stepped Cavities
FIGURE 9.34 Stepped cavities produced with a square electrode by EDM. The workpiece moves in the
two principal horizontal directions, and its motion is synchronized with the downward movement of the
electrode to produce various cavities. Also shown is a round electrode capable of producing round or
eliptical cavities. Source: Courtesy of AGIE USA Ltd.
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Wire EDM Process
FIGURE 9.35 Schematic illustration of the wire EDM process. As much as 50 hours of
machining can be performed with one reel of wire, which is then discarded.
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Laser-Beam-Machining Process
FIGURE 9.36 (a) Schematic illustration of the laser-beam-machining process. (b) and (c)
Examples of holes produced in nonmetallic parts by LBM.
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Laser Applications
APPLICATION
Cutting
Metals
Plastics
Ceramics
Drilling
Metals
Plastics
Marking
Metals
Plastics
Ceramics
Surface treatment (metals)
Welding (metals)
LASER TY PE
PCO 2; CWCO2; Nd:YAG; ruby
CWCO 2
PCO 2
PCO 2; Nd:YAG; Nd:glass; ruby
Excimer
PCO 2; Nd:YAG
Excimer
Excimer
CWCO 2
PCO 2; CWCO2; Nd:YAG; Nd:glass; ruby
Note: P = pulsed, CW = continuous wave .
TABLE 9.5 General applications of lasers in manufacturing.
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Electron-Beam-Machining Process
FIGURE 9.37 Schematic illustration of the electron-beam-machining process. Unlike
LBM, this process requires a vacuum, and hence workpiece size is limited.
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Water-Jet-Machining
FIGURE 9.38 (a) Schematic illustration of water-jet machining. (b) Examples of various
nonmetallic parts cut by a water-jet machine. Source: Courtesy of Possis Corporation.
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Abrasive-Jet-Machining Process
FIGURE 9.39 Schematic illustration of the abrasive-jet-machining process.
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Cost of Machining/Surface Finish Required
FIGURE 9.40 Increase in the cost of machining and finishing a part as a function of the
surface finish required.
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Guidant MULTI-LINK TETRATM System
FIGURE 9.41 The Guidant MULTI-LINK TETRATM coronary stent system.
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The MULTI-LINK TETRATM Pattern
FIGURE 9.42 Detail of the 3-3-3 MULTI-LINK TETRATM pattern.
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Evolution of the Stent Surface
FIGURE 9.43 Evolution of the stent surface. (a) MULTI-LINK TETRATM after lasing. Note
that a metal slug is still attached. (b) After removal of slag. (c) after electropolishing.
Manufacturing Processes for Engineering Materials, 4th ed.
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