2. Review of Machining
• Machining is a generic term, applied to material removal
processes.
• Traditional machining: turning, milling, drilling, grinding,
etc.
• Metal cutting refers to processes in which excess metal is
removed by a harder tool, through a process of extensive
plastic deformation or controlled fracture.
• Non-traditional machining: chemical machining, ECM,
EDM, EBM, LBM, machining of non-metallic materials.
3. Chemical Machining
Used to produce
shallow cavities
(<12mm) on large
areas.
Place the part in a
chemical bath (acid
or alkali depending
upon the metal)
4. Chemical
Milling
FIGURE (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.
5. Chemical-Machining Process
FIGURE (a) Schematic illustration of the
chemical-machining process.
(b) Stages in producing a profiled cavity by
chemical machining.
Note that no forces or machine tools are involved
in this process.
6. Electro-Chemical Machining (ECM)
Works on the principle
of electrolysis
Die is progressively
lowered into
workpiece as
workpiece is
dissociated into ions
by electrolysis
Electrolytic fluid flows
around workpiece to
remove ions and
maintain electrical
current path
7. Control temperature and time of exposure to
control material removal
Material removal rate is slow, 0.025-0.1
mm/min
Low DC voltage, very High current (700
amps).
Material removal rate is 2.5-12 mm/min
depending on current density.
9. Electrochemical-Machining
FIGURE Schematic
illustration of the
electrochemical-
machining process.
This process is the
reverse of
electroplating.
FIGURE Typical parts made by
electrochemical machining. (a) Turbine
blade made of a nickel alloy, 360 HB.
(b) Thin slots on a 4340-steel roller-
bearing cage.
(c) Integral airfoils on a compressor disk.
10. Electrochemical-Grinding Process
FIGURE (a) Schematic illustration of the
electrochemical-grinding process.
(b) Thin slot produced on a round nickel-alloy tube
by this process.
11. Water Jet and Abrasive
Water Jet Cutting
High pressure
water (20,000-
60,000 psi).
Can cut
extremely thick
parts (5-10
inches
possible).
Thickness
achievable is a
function of
speed.
12. Water-Jet-Machining
FIGURE (a) Schematic illustration of water-jet
machining. (b) Examples of various nonmetallic
parts cut by a water-jet machine.
15. Electron Beam Machining
Electron beam machining
Cutting and hole making on
thin materials;
very small holes and slots
(0.1-0.3mm depending on
thickness);
heat affected zone;
require vacuum, expensive
equipment; 1-2 mm3/min.
17. Laser beam machining
Cutting and hole making
on thin materials;
heat-affected zone; does
not require a vacuum;
but expensive
equipment;
consume much energy;
0.5-7.5 mm/min
depending on thickness.
18. Laser-Beam-Machining Process
FIGURE (a) Schematic illustration of the laser-
beam-machining process.
(b) and (c) Examples of holes produced in
nonmetallic parts by LBM.
19. Laser Applications
TABLE General applications of lasers in
manufacturing.
APPLICATION LASER TY PE
Cutting
Metals
Plastics
Ceramics
Drilling
Metals
Plastics
Marking
Metals
Plastics
Ceramics
Surface treatment (metals)
Welding (metals)
PCO2; CWCO2; Nd:YAG; ruby
CWCO2
PCO2
PCO2; Nd:YAG; Nd:glass; ruby
Excimer
PCO2; Nd:YAG
Excimer
Excimer
CWCO2
PCO2; CWCO2; Nd:YAG; Nd:glass; ruby
Note: P = pulsed, CW = continuous wave.
20. Machining of Nonmetallic Materials
Machining of ceramics:
Abrasive machining, including abrasive water
jet machining
Laser beam machining
Laser assisted machining
Laser assisted machining
22. 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.
23. Machining of Plastics and Composites
Plastics need to be carefully supported.
Requires large rake and relief angles, high cutting
speed, and low feed.
Trimming of plastic parts using water jet cutting or
abrasive water jet cutting.
Common problems in cutting composites
Poor edge finish, and fiber pull out.
Use abrasive water jet cutting.
Metal matrix composites such as carbide tool bits
can be machined using diamond tools, EDM, and
ECM.
26. PROCESS CHARACTERISTICS PROCESSP ARAMETE RS
AND TYPICAL MATERIAL
REMOVAL RATE OR
CUTTING SPEED
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.
0.50-7.5 m/min.
Electron-beam
machining (EBM)
Cutting and holemaking on thin
materials; very small holes and
slots; heat-affected zone; requires a
vacuum; expensive equipment.
1-2 mm
3
/min.
Water-jet machining
(WJM)
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.
Varies considerably with
workpiece material.
Abrasive water-jet
machining (AWJM)
Single or multilayer cutting of
metallic and nonmetallic materials.
Up to 7.5 m/min.
Abrasive-jet machining
(AJM)
Cutting, slotting, deburring, flash
removal, etching, and cleaning of
metallic and nonmetallic materials;
tends to round off sharp edges;
some hazard because of airborne
particulates.
Varies considerably with
workpiece material.
