NON-CONVENTIONAL MACHINING PROCESSES

NON-CONVENTIONAL
MACHINING PROCESSES
By Mohd. Hasan Akhtar
Machining… with a difference!!
That’s what Non-conventional
Machining is all about…!!!!

Types of Non-conventional Machining
Processes
1. Electrical Discharge Machining
2. Electrochemical Machining
3. Laser Beam Machining
4. Electron Beam Machining
5. Plasma Arc Cutting
6. Ultrasonic Machining
7. Water Jet Machining
8. Abrasive Jet Machining
SBJITMR, NAGPUR 2M. Hasan Akhtar
(8180818280)

The Need for Non-conventional
Machining Processes
 Traditional machining processes
• Material removal by mechanical means, such as chip forming,
abrasion, or micro-chipping
 Advanced machining processes
• Utilize chemical, electrical, and high-energy beams
 The following cannot be done by traditional processes:
a. Workpiece strength and hardness very high,>400HB
b. Workpiece material too brittle, glass, ceramics, heat-treated
alloys
c. Workpiece too slender and flexible, hard to clamp
d. Part shape complex, long and small hole
e. Special surface and dimensional tolerance requirements
(8180818280)

Classification of NTM processes
The Non-traditional Machining Methods are
classified according to the major energy sources
employed in machining.
1. Thermal Energy Methods
2. Electro - Chemical Energy Method
3. Chemical Energy Methods
4. Mechanical Energy Methods
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Classification (Contd.)
1. Thermal Energy Methods: In these methods, the
thermal energy is employed to melt and vaporize tiny particles of work-
material by concentrating the heat energy on a small area of the
workpiece. The required shape is obtained by the continued repetition
of this process.
These methods include:
a) Electrical discharge machining (EDM)
b) Laser beam Machining (LBM)
c) Plasma Arc Machining (PAM)
d) Electron Beam Machining(EBM)
e) Ion Beam Machining (IBM)
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2. Electro - Chemical Energy Method: These
methods involve electrolytic (anodic) dissolution of the workpiece
material in contact with a chemical solution.
a) Electro-Chemical Machining (ECM)
b) Electro-Chemical grinding (ECG)
c) Electro-Chemical Honing (ECH)
d) Electro-Chemical Deburring (ECD)
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3. Chemical Energy Methods: These methods involve
controlled etching of the workpiece material in contact
with a chemical solution.
1. Chemical Machining Method (CHM).
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4. Mechanical Energy Methods: In these methods,
the material is principally removed by mechanical erosion
of the workpiece material.
a) Ultra Sonic Machining (USM)
b) Abrasive Jet Machining (AJM)
c) Water Jet Machining (WJM)
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GATE-2014
The process utilizing mainly thermal energy for
removing material is
(a) Ultrasonic Machining
(b) Electrochemical Machining
(c) Abrasive Jet Machining
(d) Laser Beam Machining
M. Hasan Akhtar
(8180818280)
9SBJITMR, NAGPUR

Capabilities of NTM
1. EDM has the lowest specific power requirement and can
achieve sufficient accuracy.
2. ECM has the highest metal removal rate, MRR.
3. USM and AJM have low MRR and combined with high tool
wear, are used for non-metal cutting.
4. LBM and EBM have high penetration rates with low MRR
and, therefore, are commonly used for micro drilling, sheet
cutting, and welding.
5. CHM is used for manufacturing PCB and other shallow
components.
6. PAM can be used for clean, rapid cuts and profiles in
almost all plates upto 20 cm thick with 5o to 10o taper.
M. Hasan Akhtar
(8180818280)
10SBJITMR, NAGPUR

Shapes Cutting Capability
The various NTMM have some special shape cutting
capability as given below:
1. Micro-machining and Drilling : LBM, EBM and micro-EBM
2. Cavity sinking and standard Hole Drilling: EDM and USM
3. Fine hole drilling and Contour Machining: ECM
4. Clean, rapid Cuts and Profiles: PAM
5. Shallow Pocketing: AJM
M. Hasan Akhtar
(8180818280)
11SBJITMR, NAGPUR

GATE-2014
The following four unconventional machining processes are
available in a shop floor. The most appropriate one to drill a
hole of square cross section of 6 mm × 6 mm and 25 mm
deep is
(a) Abrasive Jet Machining
(b) Plasma Arc Machining
(c) Laser Beam Machining
(d) Electro Discharge Machining
M. Hasan Akhtar
(8180818280)
12SBJITMR, NAGPUR

Limitations of NTMM
1. Expensive set up, low MRR and skilled labour required.
2. The limitation of electrical machining methods is that
the work material must be an electrical conductor.
3. Consumption of electrical energy is very large.
4. The NTMM which have not been proved commercially
economical are: USM, AJM, CHM, EBM and PAM.
M. Hasan Akhtar
(8180818280)
13SBJITMR, NAGPUR

Process Selection
The common parameters to be taken into consideration for
selecting a particular process are the following:
1. Physical properties of the work material.
2. Type of operation required - cutting, hole making, etc.
3. Shape and size required to be produced.
4. Process capabilities; such as, expected tolerance, surface
finish, rate of metal power requirement, etc.
5. Processes economy.
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IES - 2012
Which of the following processes has very high
material removal rate efficiency?
(a) Electron beam machining
(b) Electrochemical machining
(c) Electro discharge machining
(d) Plasma arc machining
M. Hasan Akhtar
(8180818280)
15SBJITMR, NAGPUR

GATE - 2006
Arrange the processes in the increasing order of
their maximum material removal rate.
Electrochemical Machining (ECM)
Ultrasonic Machining (USM)
Electron Beam Machining (EBM)
Laser Beam Machining (LBM) and
Electric Discharge Machining (EDM)
(a) USM, LBM, EBM, EDM, ECM
(b) EBM, LBM, USM, ECM, EDM
(c) LBM, EBM, USM, ECM, EDM
(d) LBM, EBM, USM, EDM, ECM
M. Hasan Akhtar
(8180818280)
16SBJITMR, NAGPUR

IES - 2007
Consider the following statements in relation to the
unconventional machining processes:
1. Different forms of energy directly applied to the
piece to have shape transformation or material removal
from work surface.
2. Relative motion between the work and the tool is
essential.
3. Cutting tool is not in physical contact with work
piece.
(a) 1 and 2 only (b) 1, 2 and 3 only
(c) 2 and 3 only(d) 1 and 3 only
M. Hasan Akhtar
(8180818280)
17SBJITMR, NAGPUR

IES - 2009
Which one of the following statements is correct
in respect of unconventional machining
processes?
(a) The cutting tool is in direct contact with the job
(b) The tool material needs to be harder than the
job material
(c) The tool is never in contact with the job
(d) There has to be a relative motion between the
tool and the job
M. Hasan Akhtar
(8180818280)
18SBJITMR, NAGPUR

IAS - 2002
Match List I (Processes) with List II (Tolerances
obtained) and select the correct answer using the codes
given below the Lists:
List I List II
(Processes) (Tolerances obtained)
A. Plasma Arc machining 1. 7·5 microns
B. Laser Beam machining 2. 25 microns
C. Abrasive Jet machining 3. 50 microns
D. Ultrasonic machining 4. 125 microns
Codes:A B C D A B C D
(a) 4 1 3 2 (b) 3 2 4 1
(c) 4 2 3 1 (d) 3 1 4 2
M. Hasan Akhtar
(8180818280)
19SBJITMR, NAGPUR

EDM
M. Hasan Akhtar
(8180818280)
20SBJITMR, NAGPUR

Electrical Discharge Machining
SBJITMR, NAGPUR 21
 It is also known as Spark over-initiated discharge
machining, Spark erosion machining or simply Spark
machining.
 It is probably the most versatile of all the electrical
machining methods. Mechanics of material removal -
melting and evaporation aided by cavitations.
 This process may be used for machining any material,
irrespective of its hardness, which is an electrical
conductor.
M. Hasan Akhtar
(8180818280)

 The rate of metal removal and the resulting surface finish
can be controlled by proper variation in the energy and
the duration of spark discharge.
 A liquid dielectric, like paraffin or some light oil, like
transformer oil or kerosene oil, is always used in the
process.
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(EDM)
SBJITMR, NAGPUR 23
Figure 1: Schematic Diagram of EDM
M. Hasan Akhtar
(8180818280)

EDM (Contd.)
SBJITMR, NAGPUR 24
Figure 2: Schematic Diagram of EDM
M. Hasan Akhtar
(8180818280)

EDM Set-up
The main elements of this setup include
1. Power supply source
2. Dielectric medium
3. Workpiece and tool
4. Servo control
5. Speed reduction gear box
6. A rack and pinion or some other suitable mechanism for
tool feed
7. An electric circuit to generate discharge, etc.
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EDM Set-up (Contd.)
 Both, the tool and the work piece are connected to the D. C.
Electric supply source.
 The workpiece is connected to the positive terminal
 The tool to the negative terminal of the power source.
 Consequently, the work piece becomes Anode and the tool
Cathode.
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EDM Working
 The workpiece and the electrode (tool) are separated by a gap, called
Spark gap, ranges from 0.005 mm to 0.05 mm.
 This gap is filled up by the dielectric, which breaks down when a proper
voltage is applied between these two.
 A circuit voltage of 50 V to 450 V is applied, electrons start flowing from
the cathode, due to the electrostatic field, and the gap is ionized.
 The consequent drop in resistance and discharge of electric energy
results in an electrical breakdown.
 The electric spark so caused directly impinges on the surface of the
workpiece.
 It takes only a few micro seconds to complete the cycle and the spark
discharges hit the workpiece with considerable force and velocity,
resulting in the development of a very high temperature (around
10,000°C) on the spot hit by the discharges.
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EDM Working
 This forces the metal to melt, and a portion of it may be vaporized even.
 These vaporized or melted particles of the metal are thrown into the gap
by the electrostatic and electromagnetic forces, from where they are
driven away by the flowing liquid dielectric.
 It should be remembered that erosion takes place on both, the tool as well
as the workpiece, but the former is eroded much less as compared to the
latter.
 It is because the tool tip is subjected to compressive forces due to the
electric and magnetic fields, resulting in a slower erosion of the metal
from its surface.
 The rate of metal removal depends upon the discharge current, duration
of pulse and the rate of pulse repetition.
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Tool Electrode
Prime requirements EDM tool Material
1. It should be electrically conductive.
2. It should have good machinability, thus allowing easy
manufacture of complex shapes.
3. It should have low erosion rate or good work to tool
wear ratio.
4. It should have low electrical resistance.
5. It should have high melting point.
6. It should have high electron emission.
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EDM Tool
The usual choices for tool (electrode) materials are
• Copper,
• brass,
• alloys of zinc and tin,
• hardened plain carbon steel,
• copper tungsten,
• silver tungsten,
• tungsten carbide,
• copper graphite, and graphite.
M. Hasan Akhtar
(8180818280)
30SBJITMR, NAGPUR

Wear Ratio
 One major drawback of EDM is the wear that occurs on the
electrode at each spark. Tool wear is given in terms of wear
ratio which is defined as,
 Wear ratio for brass electrode is 1: 1.
 For most other metallic electrodes, it is about 3: 1 or 4: 1.
 With graphite (with the highest melting point, 3500°C), the
wear ratio may range from 5: 1 up to 50: 1.
Volume of metal removed work
Wear ratio =
Volume of metal removed tool
M. Hasan Akhtar
(8180818280)
31SBJITMR, NAGPUR

Dielectric Fluid
1. Fluid is used to act as a dielectric, and to help carry away
debris.
2. If the fluid is pumped through and out the end of the
electrode, particles will push out, and mainly collect at the
edges. They will lower the dielectric resistance, resulting in
more arcs. As a result the holes will be conical.
3. If fluid is vacuum pumped into the electrode tip, straight
holes will result.
4. Quite often kerosene-based oil.
5. The dielectric fluid is circulated through the tool at a
pressure of 0.35 N/m2 or less. To free it from eroded metal
particles, it is circulated through a filter.
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Advantages
1. Hardness, toughness or brittleness of the material poses no
problems. Due to this EDM can be used for machining
materials that are too hard or brittle to be machined by
conventional methods.
2. The method does not leave any chips or burrs on the work
piece.
3. Cutting forces are virtually zero, so very delicate and fine
work can be done.
4. The process dimension repeatability and surface finish
obtained in finishing are extremely good.
5. The characteristic surface obtained, which is made up of
craters, helps in better oil retention. This improves die life.
M. Hasan Akhtar
(8180818280)
33SBJITMR, NAGPUR

Disadvantages
1. Only electrically conductive materials can be machined by
EDM. Thus non - metallic, such as plastics, ceramics or glass,
cannot be machined by EDM.
2. Electrode wear and over-cut are serious problems.
3. A re-hardened, highly stressed zone is produced on the work
surface by the heat generated during machining. This brittle
layer can cause serious problems when the part is put into
service.
4. Perfectly square corners cannot be made by EDM.
5. High specific energy consumption (about 50 times that in
conventional machining)
6. MRR is quite low
M. Hasan Akhtar
(8180818280)
34SBJITMR, NAGPUR

Applications
The EDM process offers the following main Applications:
1. This process is very useful in tool manufacturing due to the ease with
which hard materials and alloys can be machined.
2. Re-sharpening of cutting tools.
3. Manufacturing of die
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IES - 2012
Statement (I): In Electro Discharge Machining (EDM)
process, tool is made cathode and work piece anode
Statement (II): In this process if both electrodes are
made of same material, greatest erosion takes place
upon anode
(a) Both Statement (I) and Statement (II) are individually true and
Statement (II) is the correct explanation of Statement (I)
(b) Both Statement (I) and Statement (II) are individually true but
Statement (II) is not the correct explanation of Statement (I)
(c) Statement (I) is true but Statement (II) is false
(d) Statement (I) is false but Statement (II) is true
M. Hasan Akhtar
(8180818280)
36SBJITMR, NAGPUR

GATE - 2004
The mechanism of material removal in EDM
process is
(a) Melting and Evaporation
(b) Melting and Corrosion
(c) Erosion and Cavitation
(d) Cavitation and Evaporation
M. Hasan Akhtar
(8180818280)
37SBJITMR, NAGPUR

GATE - 2003
As tool and work are not in contact in EDM
process
(a) No relative motion occurs between them
(b) No wear of tool occurs
(c) No power is consumed during metal cutting
(d) No force between tool and work occurs
M. Hasan Akhtar
(8180818280)
38SBJITMR, NAGPUR

GATE - 1999
In Electro-Discharge Machining (EDM), the tool
is made of
(a) Copper (b) High Speed Steel
(c) Cast Iron (d) Plain Carbon Steel
M. Hasan Akhtar
(8180818280)
39SBJITMR, NAGPUR

GATE-2010 (PI)
Keeping all other parameters unchanged, the tool
wear in electrical discharge machining (EDM) would
be less if the tool material has
(a) high thermal conductivity and high specific heat
(b) high thermal conductivity and low specific heat
(c) low thermal conductivity and low specific heat
(d) low thermal conductivity and high specific heat
M. Hasan Akhtar
(8180818280)
40SBJITMR, NAGPUR

GATE - 2007
In electro discharge machining (EDM), if the
thermal conductivity of tool is high and the
specific heat of work piece is low, then the tool
wear rate and material removal rate are
expected to be respectively
(a) High and high (b) Low and low
(c) High and low (d) Low and high
M. Hasan Akhtar
(8180818280)
41SBJITMR, NAGPUR

IES - 2005
Which of the following is/are used as low
wearing tool material(s) in electric discharge
machining?
(a) Copper and brass
(b) Aluminium and graphite
(c) Silver tungsten and copper tungsten
(d) Cast iron
M. Hasan Akhtar
(8180818280)
42SBJITMR, NAGPUR

GATE- 2000
Deep hole drilling of small diameter, say 0.2 mm
is done with EDM by selecting the tool material as
(a) Copper wire (b) Tungsten wire
(c) Brass wire (d) Tungsten carbide
M. Hasan Akhtar
(8180818280)
43SBJITMR, NAGPUR

ECM
M. Hasan Akhtar
(8180818280)
44SBJITMR, NAGPUR

Electro-chemical Machining
(ECM)
ECM is an extension of electroplating with some modifications, but
in a reverse direction.
Thus ECM can be describe as a controlled anodic dissolution at
atomic level of the work piece that is electrically conductive by a shaped
tool due to flow of high current at relatively low potential difference
through an electrolyte which is quite often water based neutral salt
solution.
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(ECM)
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Figure: Schematic basic Principle of Electro chemical Machining (ECM)

Electrochemical Machining
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ECM Working
1. The principle of ECM process is based on Faraday's Laws of
Electrolysis.
2. A reverse shaped tool or electrode is used in the process, which forms
cathode. The workpiece forms anode.
3. The tool and workpiece are held on each other with a very small gap
0.2mm to 2mm between them.
4. A mild D.C. Supply Voltage 2 to 35 V and Current 50A to 40,000 A is
applied between the two and an electrolyte continuously pumped into
the gap.
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ECM Working
5. Due to the applied voltage the current flows through the electrolyte
with positively charged ion being attracted towards the tool
(Cathode) and the negatively charged ions towards the workpiece
(anode).
6. The electrolyte needs to be pumped through this gap at high
pressures ranging from 0.5 to 20 bar.
7. The electrochemical reaction, taking place due to this flow of ions
results in the removal of metal from the workpiece in the form of
sludge.
8. This sludge is taken away from the gap by the flowing electrolyte
along with it.
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Faraday’s Law
First Statement: Amount of Electrochemical dissolution or deposition
proportional to amount of charge that being passed through electro
chemical Cell.
Where ‘m’ is amount of electrochemical dissolution i.e. mass and Q is
charge
Second Statement: Amount of material dissolved or deposited
depends on Electro Chemical Equivalence (ECE= Ration of Atomic
Weight and valency.)
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m Q
A
m ECE 


Faraday’s Law
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Q A It A
m  
 
' 96500
It A
m
F
F Faraday s Const C


 
3
3
( / sec)
/
m ItA IA I ECE
MRR cm
t F t F F
in gm cm
    


   

Faraday’s Law
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3
. ( / sec)
1
i i
i
i
I
MRR ECE cm
F
ECE
A
wt fraction of alloy







 For Alloy

Other Important Relations
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1
1
2
1
Re
/ ( )
s s
s
Electrode Feed Rate s S
ECE
SpecificMaterial moval Rate s
F
I
Current Density S
A
A c s area perpendicular to current flow m
V
I
R
l
R electrical resistivity
A
V
S l Gap betweentool and electrode
l

 

 
 
 



 

 

GATE-2014
The principle of material removal in Electro-
chemical machining is
(a) Fick’s law
(b) Faraday’s laws
(c) Kirchhoff’s laws
(d) Ohm’s law
M. Hasan Akhtar
(8180818280)
54SBJITMR, NAGPUR

Tool Electrode
The properties of tool materials should be:
1. High electrical and thermal conductivity
2. Easy machine-ability
3. Good stiffness
4. High corrosion resistance
 Tool materials: Copper, brass, bronze, Al, Stainless Steel, nickel, etc.
 Material wear / Tool wear: Infinite
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Electrolyte in ECM
The electrolyte is so chosen that the anode (workpiece) is dissolved but
no deposition takes place on the cathode (tool).
• Material NaCl and NaNO3
• Temperature 20oC – 50oC
• Flow rate 20 lpm per 100 A current
• Pressure 0.5 to 20 bar
• Dilution 100 g/l to 500 g/l
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Electrolyte in ECM
The electrolyte is so chosen that the anode (workpiece) is dissolved but
no deposition takes place on the cathode (tool).
Properties electrolyte should be
1. High electrical conductivity
2. Low viscosity
3. Chemical stability
4. Resistance to formation of film on workpiece surface
5. Non-corrosive and non-toxic
6. Inexpensive and readily available
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Advantages
The ECM process offers the following main advantages:
1. Hardness, toughness or brittleness of the material poses no
problems.
2. The method does not leave any chips or burrs on the work piece.
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Disadvantages
The ECM process offers the following main disadvantages:
1. Use of corrosive media as electrolytes makes it difficult to handle.
2. Sharp interior edges and corners (< 0.2 mm radius) are difficult to
produce.
3. Very expensive machine.
4. Forces are large with this method because of fluid pumping forces.
5. Very high specific energy consumption (about 150 times that
required for conventional processes),
6. Not applicable with electrically non-conducting materials and jobs
with very small dimensions
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ISRO-2009
The machining process in which the work picce is
dissolved into an electrolyte solution is called
(a) Electro-chemical machining
(b) Ultrasonic machining
(c) Electro-discharge machining
(d) Laser machining
M. Hasan Akhtar
(8180818280)
60SBJITMR, NAGPUR

PSU
ECM cannot be undertaken for
(a) steel
(b) Nickel based super alloy
(c) Al2O3
(d) Titanium alloy
M. Hasan Akhtar
(8180818280)
61SBJITMR, NAGPUR

Applications
The ECM process offers the following main Applications:
1. Machining of hard to machine and heat resistance
materials.
2. Machining of blind holes and pockets, such as in forging
dies.
3. Machining of complicated profiles, such as of jet engine
blades, turbine blades turbine wheels, etc.
4. Drilling small deep holes, such as in nozzles.
5. Machining of cavities and holes of irregular shapes.
6. Deburring of parts.
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QUIZ
1. For ECM of steel which is used as the electrolyte
a) kerosene
b) NaCl
c) Deionised water
d) HNO3
2. MRR in ECM depends on
a) Hardness of work material
b) atomic weight of work material
c) thermal conductivity of work material
d) ductility of work material
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QUIZ
3. ECM cannot be undertaken for
(a) steel
(b) Nickel based super alloy
(c) Al2O3
(d) Titanium alloy
4. Commercial ECM is carried out at a combination of
(a) low voltage high current
(b) low current low voltage
(c) high current high voltage
(d) low current low voltage
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SBJITMR, NAGPUR 65
Electron Beam
Machining
M. Hasan Akhtar
(8180818280)

Electron Beam Machining
(Principle)
 Electron Beam Machining (EBM) is a thermal process. Here a steam
of high speed electrons impinges on the work surface so that the
kinetic energy of electrons is transferred to work producing intense
heating.
 Depending upon the intensity of heating the workpiece can melt and
vaporize.
 The process of heating by electron beam is used for annealing,
welding or metal removal.
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 It is a process of machining materials with the use of a high
velocity beam of electrons.
 The workpiece is held in a vacuum chamber and the electron
beam focused on to it magnetically.
 As the electrons strike the workpiece, their kinetic energy is
converted into heat.
 This concentrated heat raises the temperature of workpiece
materials and vaporizes a small amount of it, resulting in
removal of metal from the workpiece.
 The reason for using a vacuum chamber is that, if otherwise, the
beam electrons will collide with gas molecules and will scatter.
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EBM Set-up
The main elements of Electron Beam Machining setup are shown in
Figure.
1. Vacuum Chamber, which carries vacuum of the order of l0-5 mm of
mercury.
2. Door, through which the workpiece is placed over the table in side
the chamber carries
3. The Electron gun, which is mainly responsible for emission of
electrons, consists of three main parts:
i. Tungsten filament,
ii. Grid cup and
iii. Anode.
4. The filament is connected to the - ve terminal of the D.C. Power
supply, to act as cathode, and the anode to the + ve terminal, as
shown.
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 Aperture: It captures the stray electrons, so that focused
electron beam obtained.
 Electromagnetic Lens: It works as focusing lens and focuses
the electron beam to a desired spot.
 Deflector coil: Electron beam can also be maneuvered using
the electromagnetic deflection coils for drilling holes of any
shape, though by small amount, to improve shape of the
machined holes.
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1. The filament wire is heated to a temperature of about 2500°C in the
vacuum. With the result, a cloud of electrons is emitted by the
filament, which is directed by the grid cup to travel downwards.
2. As the electrons are attracted by the anode, they pass through its
aperture in the form of a controlled beam without colliding with it.
3. A potential difference of 30 to 150 kV is maintained between the
filament and the anode.
4. As such, the electrons passing through the anode are accelerated to
achieve as high a velocity as around two-third of light.
5. The maximum velocity attained by the electrons, while passing out of
anode, is maintained by them till such time as they strike the
workpiece.
6. It becomes possible because the electrons travel through the vacuum.
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7. This high velocity electron stream, after leaving the anode, passes
through the tungsten diaphragm and then through the
electromagnetic focusing coils (or focusing lens).
8. By then, the stream is quite aligned and the focusing lens manages
to focus it precisely on to the desired spot on the workpiece.
9. The electromagnetic Deflector Coil then deflects this aligned
stream (beam) on to the work, through which the path of cut can be
controlled.
10. Further, the table on which the workpiece is loaded, can also be
traversed to feed the workpiece as needed.
11. This high velocity beam of electrons impinges on the workpiece,
where its kinetic energy is released and gets converted into heat
energy. The high intensity heat, so produced, melts and vaporizes
the work material at the spot of beam impingement.
(8180818280)

Mechanism of MRR
 Thermo ionic electrons (As the potential difference is applied between
cathode and anode, electrical filament get heated near about at 2500
C and emits electron which are repelled by cathode and attract by
anode)
 Acceleration of electron due to anode potential (Accelerated to almost
half of the velocity of light)
 High velocity beam of electron
 Shaping and focusing of electron beam (this electron beam is shaped
and focused by a series of magnetic and electro magnetic lenses)
 Impingement of high velocity electron beam on the work
 Spot size 10 to 100 microns, high energy density (10^4 watt/mm2)
 Heating, melting and vaporization leading to drilling
(8180818280)

(8180818280)
 EBM Process Parameters
• The accelerating voltage (30 to 150kV)
• The beam current (250 A to 1A)
• Pulse duration (50 s to 50ms)
• Energy per pulse (100J/Pulse)
• Power per pulse
• Lens current
• Spot size (10 m to 100 m)
• Power density

 


GATE-2016
The non-traditional machining process that
essentially requires vacuum is
(a) electron beam machining
(b) electro chemical machining
(c) electro chemical discharge machining
(d) electro discharge machining
M. Hasan Akhtar
(8180818280)
79SBJITMR, NAGPUR

Advantages
The EBM process offers the following main advantages:
1. Workpiece is not subjected to any physical or metallurgical
damage because about 25-50 μm away from machining spot
remains at room temperature and so no effects of high
temperature on work.
2. Problem of tool wear is non-existent. So, close dimensional
tolerances can be achieved.
3. Heat can be concentrated on a particular spot.
4. An excellent technique for micro machining and Any material
can be machined.
5. Highly reactive metals like Al and Mg can be machined very
easily.
(8180818280)

Disadvantages
The EBM process offers the following main disadvantages:
1. Material removal rate is very low compared to other
unconventional machining processes.
2. Maintaining perfect vacuum is very difficult moreover Workpiece
size is limited due to requirement of vacuum in the chamber.
3. The machining process can’t be seen by operator.
4. Not suitable for producing perfectly cylindrical deep holes.
5. High power consumption.
6. Difficult to produce slots and holes of uniform shapes and
dimensions.
(8180818280)

Applications
The EBM process offers the following main Applications:
1. Very effective for machining of materials of low heat
conductivity and high melting point.
2. Micro-machining operations on workpieces of thin sections.
3. Micro-drilling operations (up to 0.002 mm) for thin orifices,
dies for wire drawing, parts of electron microscopes, fiber
spinners, injector nozzles for diesel engines etc.
4. Used only for circular holes.
(8180818280)

SBJITMR, NAGPUR 83
Laser Beam
Machining
M. Hasan Akhtar
(8180818280)

Laser Beam Machining
(Principle)
 Laser beam machining (LBM) uses the light energy from a laser
device for the material removal by vaporization.
 Laser is the term used for the phenomenon of 'amplification of
light’ by stimulated emission of radiation’.
 A laser is an optical transducer that converts electrical energy into a
highly coherent light beam.
 The energy of the coherent light beam is concentrated not only
optically but also with time.
(8180818280)

Laser Beam Machining
 The setup consists of a stimulating light source (like flash lamp) and
a laser rod.
 The light radiated from the flash lamp is focused on to the laser rod
(Laser tube), from where it is reflected and accelerated in the path.
 This light is emitted in the form of a slightly divergent beam. A lens
is incorporated suitably in the path of this beam of light which
converges and focuses the light beam on to the workpiece to be
machined.
 This concentration of the laser beam on the workpiece melts the
work material and vaporizes it.
 It is very costly method and can be employed only when it is not
feasible to machine a workpiece through other methods.
(8180818280)

(8180818280)

M. Hasan Akhtar
(8180818280)
SBJITMR, NAGPUR 87

LBM Set-up
It mainly consists of
 Laser tube or rod, the types of lasers used in LBM are carbon
dioxide gas lasers and solid-state lasers.
 Pair of mirrors - one at each end of the tube,
 Flash tube or lamp (energy source),
 Amplifying source (laser),
 Power supply source,
 Cooling system and
 Lens (focusing source).
The main setup is fitted inside an Enclosure, which carries a highly
reflective surface inside.
(8180818280)

LBM Operation
 In operation, the optical energy (light) is thrown by the flash lamp on to
the laser tube (Ruby rod).
 This excites the atoms of the inside media, which absorb the radiation
of incoming light energy.
 This results in the to and fro travel of light between the two reflecting
mirrors. But, the partial reflecting mirror does not reflect the total light
back and a part of it goes out in the form of a coherent stream of
monochromatic light.
(8180818280)

LBM Operation
 This highly amplified stream of light is focused through a lens, which
converges it to a chosen point on the workpiece.
 This high intensity converged laser beam, when falls on the workpiece,
melts the workpiece material, vaporizes it almost instantaneously
and penetrates into it.
 Thus, it can be called a type of thermal cutting process.
(8180818280)

LBM Operation
(8180818280)

Advantages
The LBM process offers the following main advantages:
1. Any material can be easily machined irrespective of its
structure and physical and mechanical properties.
2. Unlike conventional machining, there is no direct contact
between the tool and the workpiece and no involvement of
large scale cutting forces.
3. Can be effectively used for welding of dissimilar metals as well
4. Small heat effected zone around the machined surface.
5. Very small holes and cuts can be made with fairly high degree
of accuracy.
(8180818280)

Disadvantages
The LBM process offers the following main disadvantages:
1. High capital investment needed.
2. Operating cost is also quite high.
3. Highly skilled operators are needed.
4. Production rate is low.
5. Its application is limited to only the thin sections and where
a very small amount of metal removal is involved.
6. Cannot be effectively used to machine highly heat
conductive and reflective materials.
(8180818280)

Applications
The LBM process offers the following main Applications:
1. Trimming of carbon resistors.
2. Drilling small holes in hard materials like tungsten and
ceramics.
3. Cutting complex profiles on thin and hard materials.
4. Cutting or engraving patterns on thin films.
5. Dynamic balancing of precision rotating components,
such as of watches.
6. Trimming of sheet metal and plastic parts.
(8180818280)

Ultrasonic Machining
M. Hasan Akhtar
(8180818280)
95SBJITMR, NAGPUR

M. Hasan Akhtar
(8180818280)
96SBJITMR, NAGPUR

Subsystems of USM
B
E
C
D
A
M. Hasan Akhtar
(8180818280)
97SBJITMR, NAGPUR

(8180818280)

Transducer
 The ultrasonic vibrations are produced by the transducer.
The transducer is driven by suitable signal generator
followed by power amplifier. The transducer for USM works
on the following principle
Piezoelectric effect
Magnetostrictive effect
Electrostrictive effect
 Magnetostrictive transducers are most popular and robust
amongst all.
M. Hasan Akhtar
(8180818280)
99SBJITMR, NAGPUR

GATE -2010 (PI)
Ultrasonic machines, used in material removal processes,
require ultrasonic transducers. The transducers works on
different working principles. One of the working principles of
such ultrasonic transducers is based on
(a) eddy current effect (b) Seebeck effect
(c) piezo-resistive effect (d) piezo-electric effect
M. Hasan Akhtar
(8180818280)
100SBJITMR, NAGPUR

Tool Electrode in USM
 The tool is made of relatively soft metal.
 It is applied to the workpiece surface and the Slurry applied
either manually or through a pump.
 The tool can be attached to the arbor either by brazing, hard
soldering or screwing.
 Sometimes hollow tools are used which facilitate feeding of
the slurry through them.
 The main advantage of this process is that the workpiece
after being machined is normally free from residual
mechanical stresses and a high degree of surface finish can
be obtained.
(8180818280)

 A high frequency electric current is sent by the ultrasonic oscillator to
the ultrasonic transducer.
 The function of the transducer is to convert this electrical energy into
mechanical vibrations.
 The vibrations so generated are of the order of 20 kHz to 30 kHz,
although the available amplitude usually varies from 15 – 50 μm .
 The transducer is made of a magneto strictive material, which is
excited by the following high frequency electric current and this
results in the generation of mechanical vibrations.
 These vibrations are then transmitted to the cutting fool via the
intermediate connecting parts, such as transducer cone or horn,
connecting body and tool holder.
(8180818280)

 Slurry of small abrasive particles is forced against the work by means of
a vibrating tool, removing the workpiece material in the form of
extremely small chips.
 The grains used are of silicon carbide, aluminum oxide, boron carbide
or diamond dust.
 This processes is suitable only for hard and brittle materials like
carbides, glass, ceramics, silicon, precious stones, germanium,
titanium, tungsten, tool steels, die steels, ferrite quartz, etc.
 The vibrating frequency used for the tool is of the order of over 20,000
oscillations second.
 Such a high frequency, which is more than the upper limit of audible
frequency for human ear' makes the process inaudible (silent).
(8180818280)

 This makes the tool vibrate in a longitudinal direction, as,
shown.
 The intermediate parts together form what is known as the
focusing unit and the cutting tool is fastened at its end.
 The shape of the cutting tool is the same as that of the
cavity to be produced by it.
 The slurry, formed by the suspension of abrasive grains in
a carrier fluid, is fed into the machining area by means of a
circulating pump.
 However, in order to keep its temperature low a suitable
cooling system may be incorporated.
(8180818280)

Process Parameters
M. Hasan Akhtar
(8180818280)
106SBJITMR, NAGPUR

Effect of machining parameters on MRR
•Feed force (F)
•Amplitude of vibration (ao)
•average grit diameter, dg
•Frequency of vibration (f)
•Volume concentration of
abrasive in water slurry – C
M. Hasan Akhtar
(8180818280)
107SBJITMR, NAGPUR

GATE-2016
In an ultrasonic machining (USM) process, the material
removal rate (MRR) is plotted as a function of the feed
force of the USM tool. With increasing feed force, the
MRR exhibits the following behaviour:
(a) increasing linearly
(b) decreases linearly
(c) does not change
(d) first increases and then decreases
M. Hasan Akhtar
(8180818280)
108SBJITMR, NAGPUR

Advantages
The USM process offers the following main Advantages:
1. Extremely hard and brittle materials can be easily machined.
2. Highly accurate profiles and good surface finish can be easily
obtained.
3. The machined Workpiece are free of stresses.
4. Metal removal cost is low.
5. Due to practically no heat generation in the process, the physical
properties of the
6. Work material remain unchanged.
7. The operation is noiseless.
8. Operation of the equipment is quite safe.
(8180818280)

Disadvantages
The USM process offers the following main Advantages:
1. The metal removal rate is low.
2. The initial equipment cost is higher than the conventional machine tools.
3. This process does not suit to heavy metal removal.
4. The cost of tooling is also high.
5. Difficulties are encountered in machining softer materials.
6. Power consumption is quite high.
7. High wear rate of tool may lead to dimensionally inaccurate machined parts.
So, for accurate machining, the tool may have to be replaced quite often,
especially while machining blind cavities.
8. In order to maintain an efficient cutting action, the slurry may have to be
replaced periodically
9. The size of the cavity that can be machined is limited.
(8180818280)

Applications
The USM process offers the following main Applications:
1. Used for machining hard and brittle metallic alloys, semiconductors,
glass, ceramics, carbides etc.
2. Used for machining round, square, irregular shaped holes and
surface impressions.
3. Machining, wire drawing, punching or small blanking dies.
(8180818280)

Note
 The following material is generally machined by
USM
(i) Glass
(ii) Silicon
(iii) Germanium
 Tool in USM is generally made of Steel
M. Hasan Akhtar
(8180818280)
112SBJITMR, NAGPUR

GATE - 1994
Ultrasonic machining is about the best process
for making holes in glass which are comparable
in size with the thickness of the sheet.
The above statement is
(a) True
(b) False
(c) Cant say
(d) Insufficient data
M. Hasan Akhtar
(8180818280)
113SBJITMR, NAGPUR

IES 2011
USM has good machining performance for :
(a) Al
(b) Steel
(c) Super alloys
(d) Refractory material
M. Hasan Akhtar
(8180818280)
114SBJITMR, NAGPUR

GATE - 1993
In ultrasonic machining process, the material
removal rate will be higher for materials with
(a) Higher toughness
(b) Higher ductility
(c) Lower toughness
(d) Higher fracture strain
M. Hasan Akhtar
(8180818280)
115SBJITMR, NAGPUR

GATE - 1992
In Ultrasonic Machining (USM) the material
removal rate would
(a) Increase
(b) Decrease
(c) Increase and then decrease
(d) decrease and then increase
with increasing mean grain diameter of the abrasive
material.
M. Hasan Akhtar
(8180818280)
116SBJITMR, NAGPUR

IES - 2009
By which one of the following processes the
metering holes in injector nozzles of diesel
engines can be suitably made?
(a) Ultrasonic machining
(b) Abrasive jet machining
(c) Electron beam machining
(d) Chemical machining
M. Hasan Akhtar
(8180818280)
117SBJITMR, NAGPUR

IES - 2006
During ultrasonic machining, the metal removal
is achieved by
(a) High frequency eddy currents
(b) high frequency sound waves
(c) Hammering action of abrasive particles
(d) Rubbing action between tool and workpiece
M. Hasan Akhtar
(8180818280)
118SBJITMR, NAGPUR

IAS - 1996
During ultrasonic machining, the metal removal
is affected by the
(a) Hammering action of abrasive particles
(b) Rubbing action between tool and workpiece
(c) High frequency sound waves
(d) High frequency eddy currents
M. Hasan Akhtar
(8180818280)
119SBJITMR, NAGPUR

GATE-2016 (PI)
Consider the following statements.
(P) Electrolyte is used in Electro-chemical machining.
(Q) Electrolyte is used in Electrical discharge machining.
(R) Abrasive-slurry is used in Ultrasonic machining.
(S) Abrasive-slurry is used in Abrasive jet machining.
Among the above statements, the correct ones are
(a) P and R only (b) Q and S only
(c) Q, R and S only (d) P and Q only
M. Hasan Akhtar
(8180818280)
120SBJITMR, NAGPUR

What is PLASMA?
 When gases are heated to temperatures above 5500°C,
they are ionized and exist in the form of a mixture of free
electrons, positively charged ions and neutral atoms.
This mixture is termed as plasma.
 The temperature of central part of plasma goes as high
as between 11000°C to 28000°C, where the gas is
completely ionized.
(8180818280)

Plasma Arc Machining
(8180818280)

PAM Set-up Description
 The Plasma-arc cutting torch carries a tungsten electrode
fitted in a Small chamber.
 This electrode is connected to the negative terminal of a D.C.
power supply source and, therefore, acts as a cathode.
 The other (+ve) terminal of the power supply is conceded to
the nozzle formed near the bottom of the chamber. The nozzle
acts as an anode.
 On one side of the torch is provided a passage for supply of
gas into the chamber.
 There is also a provision of water circulation around the torch
so that the electrode and the nozzle both remain water cooled.
(8180818280)

Plasma Arc Machining
 In Plasma arc machining or Plasma arc cutting, a high velocity
jet of this high temperature ionized gas is directed on to the
workpiece surface by means of a well-designed torch.
 This jet melts the metal of the workpiece and displaces the
molten metal away from its path. The heating of workpiece
material is not due to any chemical reaction but on account
of the continuous attack of electrons which transfer the
heat energy of high temperature ionized gas to the work
material.
 This process can, therefore, be safely used for machining of any
metal, including those which can be subjected to chemical
reaction.
(8180818280)

Plasma Arc Machining (MRR)
 A strong arc is struck between the electrode (cathode) and the
nozzle (anode) and the gas forced into the chamber.
 As the gas molecules collide with the high velocity electrons of
the arc, the former get ionized and a very large amount of heat
energy is evolved.
 The flow of gas is so controlled that the arc remains stable. This
high velocity stream of hot ionized gas, called plasma, is
directed on to the workpiece to melt its material and also blow it
away.
(8180818280)

Gas or Gas-Mixture in PAM
 The choice of a particular gas for use in this process
depends on the expected quality of finish on the cut
surface and economic considerations.
 Any gas or gas-mixture which does not adversely affect the
electrode or the workpiece materials can be safely used.
 Rate of flow of the gas will be governed by the application
requirements.
 It can be said that it will vary directly as the thickness of the
workpiece.
 The commonly used gases and gas-mixtures used in the
process are given in Table below.
(8180818280)

Advantages
The PAM process offers the following main Advantages:
1. It gives faster production rate.
2. Very hard and brittle metals can be machined.
3. Small cavities can be machined with good dimensional
accuracy.
(8180818280)

Disadvantages
The PAM process offers the following main Advantages:
1. Its initial cost is very high.
2. The process requires over safety precautions which further
enhance the initial cost
3. Some of the workpiece materials are very much prone to
metallurgical changes on excessive heating so this fact
imposes limitations to this process.
4. It is uneconomical for bigger cavities to be machined.
(8180818280)

Applications
The PAM process offers the following main Applications:
1. Cutting of stainless steel and non-ferrous metals (such as
aluminium alloys), particularly their profile cutting.
2. With feasibility of its use under water, it is used in
shipyards.
3. Other industries using this technique include nuclear
power plants, chemical industries, etc.
4. Also, this technique has been successfully used for
turning and milling of 'hard to machine’ materials.
(8180818280)

Water Jet Machining
 A high velocity water jet is made to impinge on to the
workpiece. This jet pierces the work material and performs a
sort of slitting operation.
 Water, under pressure, from a hydraulic accumulator is
passed through the orifice of a nozzle to increase its
velocity.
 The nozzle orifice size (dia.) usually varies from 0.08 mm to
0.5 mm and the exit velocity of the water jet up to 920
m/sec.
(8180818280)

Water Jet Machining
(8180818280)

Water Jet Machining
1. In this process, abrasive particles are added to the high velocity stream
of water jet.
2. Thus, it is the high velocity stream of hydro abrasive jet which is made
to impinge on to the work material.
3. In this process, the nozzle carries a mixing chamber (or abrasive tube)
at its end.
4. The abrasive particles are thrown into the water jet coming out of the
nozzle and the mixture of the two (water and abrasives) comes out of
the chamber (or tube) in the form of a high velocity water-abrasive jet
to be directed on to the workpiece.
5. The material is removed due to combined effect of abrasion and
impact. With the use of proper abrasive and adequate water pressure
any material can be cut through this process.
(8180818280)

Water Jet Machining
 It is reckoned that the cut (slit) produced in the workpiece is lightly
(about 0.025 mm) larger than the diameter of the jet.
 The water pressures used in the process vary from 2100kg/cm2 to
3500kg/cm2.
 Commonly used abrasives are silica, aluminium oxide and garnet and
their grit sizes 60, 80, 100 and 120 .
 The mixing chamber or abrasive tube is usually made of extremely hard
and wear resistant material like carbide.
 Usually a gap of 0.5 mm to 1.5 mm is necessary between the work
surface and the tip of the tube.
(8180818280)

Advantages
The WJM process offers the following main Advantages:
1. In most of the cases, no secondary finishing required
2. Low cutting forces on workpieces
3. Limited tooling requirements
4. Little to no cutting burr
5. Very good surface finish(125-250 microns)
6. No heat affected zone
7. Eliminates thermal distortion and structural change
8. Precise, multi plane cutting of contours, shapes, and bevels of any
angle.
(8180818280)

Disadvantages
The WJM process offers the following main Advantages:
1. Cannot drill flat bottom
2. Cannot cut materials that degrades quickly with moisture
3. Surface finish degrades at higher cut
4. High capital cost and high noise levels during operation.
(8180818280)

Applications
The WJM process offers the following main Applications:
1. Cleaning and descaling operations.
2. To machine nonmetallic materials like paper boards,
wood, plastics, asbestos and rubber etc.
(8180818280)

Abrasive Jet Machining
 This process consists of directing a stream of fine abrasive grains
mixed compressed air or some other gas at high pressure, through
a nozzle on to the surface of the workpiece to be machined.
 These particles impinge on the work surface at high speed and the
erosion, caused by their impact enables the removal of metal.
 The abrasive and fed into the mixing particles are contained in a
suitable holding device, like hopper and fed into the mixing
chamber.
 A regulator is incorporated in the line to control the flow of abrasive
particles.
 Compressed air or high pressure gas is supplied to the mixing
chamber through a pipe line.
(8180818280)

(8180818280)

 This pipe line carries a pressure gauge and a regulator to
control the gas flow and its pressure. the mixing chamber,
carrying the abrasive particles, is vibrated and the
amplitude of these vibrations controls the flow of abrasive
particles.
 These particles mix in the gas stream, travel further through
a hose and finally pass through the nozzle at a
considerably high speed, impinges on the work surface
causes the removal of metal.
 This outgoing high speed stream mixture of gas and
abrasive particles is known as Abrasive jet.
(8180818280)

Advantages
The AJM process offers the following main Advantages:
1. Can be used in any material, conductive, non-conductive, ductile or
brittle
2. Good dimensional accuracy (±0.05 mm)
3. Good Surface finish – 0.25 to 1.25 µm
4. Due to cooling action of gas stream no thermal damage on the work
surface
5. Due to negligible force delicate workpiece can be machined.
(8180818280)

Disadvantages
The AJM process offers the following main Advantages:
1. It is not suitable for machining of ductile materials.
2. Metal removal is slow.
3. Machining accuracy is relatively poorer.
4. There is always a danger of abrasive particles getting
embedded in the work material. Hence, cleaning needs to
be necessarily done after the operation.
5. The abrasive powder used in the process cannot be
reclaimed or reused.
6. Possibility of stray cutting
(8180818280)

Applications
The AJM process offers the following main Applications:
1. Cutting and drilling on metal foils and thin sections of
ceramics and glass
2. Intricate holes in electronic components such as resistor
paths in insulation
3. Engraving of characters on toughened glass automobile
windows
4. Cleaning, polishing and deburring the surface
(8180818280)

Quiz
3. Material removal takes place in AJM due to
(a) electrochemical action
(b) mechanical impact
(c) fatigue failure of the material
(d) sparking on impact
4. As the stand off distance increases, the depth of
penetration in AJM
(a) increases
(b) decreases
(c) does not change
(d) initially increases and then remains steady
(8180818280)

Quiz
1. AJM nozzles are made of
(a) low carbon steel
(b) HSS
(c) WC
(d) Stainless steel
2. Material removal in AJM of glass is around
(a) 0.1 mm3/min
(b) 15 mm3/min
(c) 15 mm3/s
(d) 1500 mm3/min
(8180818280)

Economics of Advanced Machining
Processes
 High cost of equipment, which typically
includes computer control
 May use hard tooling, soft tooling, or both
 Low production rates
 Can be used with difficult-to-machine
materials
 Highly repeatable
 Typically requires highly skilled operators
(8180818280)

THANK YOU
(8180818280)

NON-CONVENTIONAL MACHINING PROCESSES

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