NON TRADITIONAL MACHINING & MATERIAL ADDITION PROCESS ( as per MGU syllabus)

Department of Mechanical Engineering SSET 2014
Page1
Module V
Modern machining methods are also named as non-conventional machining methods. Non
traditional machining processes, are employed where traditional machining processes are not
feasible, satisfactory or economical due to special reasons as outlined. The complexity of the
job profile, hard materials, need for smooth surface finish, closer dimensional tolerance and
higher accuracy has led to the unconventional machining processes more important
Characteristics of unconventional process
1. Very hard and brittle can be machined
2. Flexible or slender work piece be machined, due to absence of physical contact of
tool and work (less cutting force)
3. Complex part geometries that can be produced
4. Provide very good quality of surface finish and dimensional accuracy
5. Stress free components are possible
6. Less tool wear due the absence of tool contact
Disadvantages of non-conventional machining:
1) High cost
2) complex set-up
3) skilled operator required
Conventional machining involves the direct contact of tool and work -piece, whereas
unconventional machining does not require the direct contact of tool and work piece.
Conventional machining has many disadvantages like tool wear which are not present in non-
conventional machining.
Machining performance characteristics of non conventional process
The machining characteristics of non-conventional processes can be analyzed with respect to:
(i) Metal removal rate
(ii) Tool wear rate
(iii) Surface finish and Tolerance obtained
(iv) Depth of surface damage
(v) Power required for machining
Classification of non-conventional machining processes
Classification based on principle of working and energy is described below. The suitability of
application of any of the processes is dependent upon various performance factors.

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The process capabilities of non-conventional manufacturing processes have been compared in
table.
 The metal removal rates by ECM and PAM are respectively that of conventional
whereas others are only small fractions of it.
 Power requirement of ECM and PAM is also very high
 ECM has very low tool wear rate
 The capital cost of ECM is very high whereas capital costs for AJM and PAM are
comparatively low.
 EDM has got higher tooling cost than other machining processes.
 The metal removal efficiency is very high for EBM and LBM than for other
processes.

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Chemical machining processes (CHM)
This process is also called etching. The part of the workpiece whose material is to be
removed is brought into the contact of chemical called enchant. The metal is removed by the
chemical attack of enchant. The portion of workpiece where no material is to be removed is
masked (maskant) before chemical etching. Chemical machining has been used where close
tolerances are required. The surface finish obtained by the process is of the order of 0.5 to 2
microns.
Common maskants used are neoprene, polyvinylchloride, polyethylene etc. Enchant is
selected depending on the workpiece material, rate of material removal and surface finish
required. Common enchants are H2SO4, Fe CL3, HNO3.
Advantages
1. Different work can be done simultaneously.
2. No application of force so no risk of damage to delicate or low strength work-piece
3. Complicated shapes/patterns can be machined.
4. Machining of hard and brittle material is possible.
5. Low capital cost of equipment
6. Easy and quick design changes
7. The good surface quality
Disadvantages
1. Difficult to get sharp corner
2. Difficult to machine thick material. Limited to thin layer removal
3. Slower process, very low MRR so high cost of operation.
4. Causes less dimensional accuracy
Common application
 Creating shallow, wide cavities on plates, sheets, forgings and castings to reduce weight.
 Chemical Blanking: Metal blanks can be cut from very thin sheet metal
 Chemical Milling: is used in the aerospace industry to remove shallow layers of
material from large aircraft components.
 Etching is used widely to manufacture integrated circuits and microelectromechanical
systems components, decorative ornaments, filters or strainers etc

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Electrochemical machining (ECM)
In ECM, a dc voltage (10-25 V) is applied across the gap between a pre-shaped cathode tool
and an anode workpiece. The workpiece is dissolved by an electrochemical reaction to the
shape of the tool. ECM is the reverse of the electroplating. This process works on the
principle of Faraday‘s laws of electrolysis.
Tool is made cathode and kept in close proximity to the work-piece (anode) and current is
passed through the circuit. The electrolyte is continuously flowing through a hole in the tool
to the gap between the work piece and the tool surfaces. Material of work piece is removed by
anodic dissolution. At the anodic workpiece surface, metal is dissolved into metallic ions by
the deplating reaction, and thus the tool shape is copied into the workpiece. In ECM,
electrolyte is so chosen that there is no deposition on tool and shape of tool remains
unchanged. The machined surface takes the replica of tool shape
Dissolution reaction of iron (work material) in sodium chloride (NaCl) electrolyte
The result of electrolytic dissociation
and
Negatively charged anions: (OH)-
and Cl-
towards to anode,
Positively charged cations: H+
and Na+
towards to cathode.
At the anode:
2
2
)()(2
2
2
OHFeOHFe
FeClClFe
eFeFe






At the cathode, the reaction generates hydrogen gas
222 HeH  
The outcome of these electrochemical reactions is that the iron ions combine with other ions
to precipitate out as iron hydroxide Fe (OH)2 and Fe Cl2 as sludge.

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Electrolyte
Water is used as base of electrolyte in ECM. Normally water soluble NaCl and NaNO3 are
used as electrolyte. Electrolyte facilitates are carrier of dissolved workpiece material. It is
recycled by a pump after filtration.
The main functions of the electrolytes in ECM are to
1. Create conditions for anodic dissolution of workpiece material
2. Remove the debris of the electrochemical reactions from the gap
3. Carry away the heat generated by the machining process
Properties of electrolyte
1. Ensure a uniform and high-speed anodic dissolution
2. Not deposit on the cathode surface, so that the cathode shape remains unchanged
3. Have a high electrical conductivity and low viscosity to reduce heat generation
and to ensure good flow conditions in the extremely narrow inter-electrode gap
4. Be safe, non-toxic, low cost and less erosive to the machine body
5. Have small variation in its conductivity and viscosity due to temperature rise
Tool Feed Mechanism
Servo motor is used to feed the tool to the machining zone. It is necessary to maintain a
constant gap between the workpiece and tool so tool feed rate is kept accordingly while
machining.
Process parameters and performance factors
 Supply voltage = 8 to 20V,
 Current (I) = 50 to 5000 A.
 Electrode gap is typically 0.1 to 0.2 mm.
 Tool material - Cu, Brass, Steel
 Tool feed rate,
 Electrolyte composition and temperature etc
 MRR is about 1600mm3
/min per 1000 A
 Surface finishes 0.1 to 0.5 microns using ECM
 Specific power consumption 7W/mm3
/min
Accuracy and surface finish of ECM product is influenced on following input factors
 Machining voltage
 Feed rate of electrode
 Temperature and concentration of electrolyte
Advantages of ECM Process or process capabilities
1. Machining of hard and brittle material is possible with good surface finish
2. Good for complicated shapes.
3. There is almost negligible tool wear so cost of tool making is one time
4. No direct contact between tool and work and absence of force or heat, so no scope of
mechanical and thermal residual stresses in the work-piece.
5. Very good surface finish can be obtained.
6. MRR is not dependent on material hardness.

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Disadvantages and Limitations of ECM
1. Electricity non-conducting materials can not be machined.
2. Tool and workpiece material should be chemically stable with the electrolyte
3. Accurate feed rate of tool is required to be maintained.
4. High cost and difficult in dimensional control
Applications of ECM Process
1. Used to machine dies, turbine and compressor blades
2. ECM is used for deburring of parts like gears.
3. ECM has been used in a wide variety of industrial applications ranging from cavity
sinking to deburring.
Heat affected zone (HAZ)
Since it is a chemical process where generation of heat is very less, there is no heat affected
zone comparing with other non traditional machining process.
Material removal mechanism
Material is removed on the basis of anodic dissolution in an electrolytic cell.
Material removal rate (MRR) calculation in ECM process
Electrochemical dissolution is governed by Faraday‘s laws
The first law states that the amount of electrochemical dissolution or deposition is
proportional to amount of charge passed through the electrochemical cell
tIm *
where m = mass of material dissolved or deposited
I = current intensity
t=time
The second law states that the amount of material deposited or dissolved further depends
directly on atomic weight and inverse of valency of material.
Combining both laws, we get
n
N
tIm **
dn
N
tIMRR
*
***
96500
1

removedmaterialofvolumeMRR
materialofdensityd
timet
valencyn
weightatomicN
tconsmicalelectrochewhere





 tan
96500
1

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Electric discharge machining (EDM)
It is also known as spark erosion machining or spark machining. Material of workpiece
removed due to erosion caused by electric spark. The metal electrode (tool) and the part
(work) are placed very close to each other, separated by a non-conducting liquid (called a
dielectric) – a commonly used dielectric is kerosene. A voltage difference is then applied to
the part and tool, generating a spark; the heat from the spark melts a tiny bit of metal from the
partThe melted metal cools and solidifies as tiny particles in the dielectric. By pumping the
dielectric to flow, the metal is carried away, and the process continues. (When potential
difference is created across the two surfaces of dielectric fluid, it gets ionized). Servo
mechanism is provided to make the tool feed as the machining is taking place to keep the gap
constant.
 Voltage 50 to 450 V (DC)
 Electrode gap = 0.01 to 0.5 mm
 MRR: 2 to 400 mm3
/min.
 Ra varies from 0.05 – 12.5 μm
Tool/ electrodes in EDM
The geometry which is to be machined into the workpiece decides the shape and size of the
tool. The electrode is conductor, usually copper, graphite, tungsten and brass etc. Tool is
given negative polarity. The tool material selected should be easy to machine, high wear
resistant. Tool is made slightly under size for inside machining and over sized for cut side
machining.
1. High electrical conductivity
2. High thermal conductivity –the local temperature rise would be less
3. High melting point – high melting point leads to less tool wear
4. Easy manufacturability
5. Cost – cheap
6. Less wear rate
Dielectric Solution
Important properties of dielectric are its dielectric strength, viscosity, thermal conductivity
and thermal capacity. Dielectric strength characterizes the fluid‘s ability to maintain high
resistivity before spark discharge and the ability to recover rapidly after the discharge.

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The functions of a dielectric fluid in EDM process
• It acts as an insulating medium
• To act as a coolant to quench the spark and to cool the tool and work piece.
• To carry away the metal particles and to maintain the gap for smooth operation.
Mineral oils (kerosene) are commonly used as the oils exhibiting high dielectric strength and
a low viscosity. Water based dielectrics are used almost extensively for wire EDM
operations.
Properties of dielectric fluid
1. Low viscosity to ensure efficient flushing
2. High flash point
3. Non-toxic
4. Non-corrosive
5. High latent heat
6. Suitable dielectric strength
Tool Feed Mechanism
In case of EDM, feeding the tool means controlling gap between workpiece and the tool. This
gap is maintained and controlled with the help of servo mechanism. The electrode gap
normally varies from 0.005 mm to 0.50 mm. Since tool wear is expected, tool wear rate is a
performance parameters.
Advantages or process capability of EDM
1. Can machine hard material economically with close tolerance.
2. High degree of dimensional accuracy, so recommended for tool and die making.
3. Complicated geometries can be produced which are very difficult otherwise.
4. Highly delicate sections and weak materials can be processed without any risk of
their distortion, because tool never applies direct contact on the workpiece
5. Fine holes can be drilled easily and accurately.
6. A good surface finish can be obtained.
Disadvantages and Limitations of EDM Process
1. Electrically non-conducting materials cannot be processed by EDM.
2. EDM process is not capable to produce sharp corners.
3. The slow rate of material removal.
4. Specific power consumption is very high.
5. Excessive Tool wear affects dimensional accuracy
6. Cannot be used on large sized workpieces, size is constrained by the size of set up.
Application of Electric Discharge Machining
EDM is widely used for die making as complex cavities are to be made, cutting very small
and accurate dimension holes, e.g. in injection nozzles for motor engines etc. This process is
highly economical for machining of very hard material as tool wear is independent of
hardness of workpiece material. It is very useful in tool manufacturing. It is also used for
making holes with straight and curved axes which cannot be produced by conventional
machining operations.

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Process parameters of EDM
Many processes variables influence the performance like material removal rate, surface finish
and tool wear etc. Few controllable main input variables are the following:
1. Current – I (current passing in the circuit)
2. Pulse on time –- ton (duration of spark during a cycle)
3. Pulse off time - toff (duration of absence of spark during a cycle)
4. Open circuit voltage – V
5. The gap between the workpiece and the tool – spark gap
Voltage and current variation during EDM process
Similarities between EDM and ECM (draw both figures also)
 The tool and workpiece are separated by a very small gap, i.e. no contact in between
 The tool and material must be conductors of electricity.
 A fluid is used as a medium between the tool and the work
 The tool is fed continuously towards the workpiece to maintain a constant gap
 Needs high capital investment and power
In electro-discharge machining, the occurrence of sparks cause material removal in the form
of craters. These craters are due to melting and vaporization of workpiece over a localized
area under the spark, which acts as the heat source. MRR is basically a function of the current
and the melting point of the work-piece material. But experimentally we consider metal
removal is function of pulse energy and frequency. Nature of variation of crater diameter,
crater depth and volume of material removed with respect to different machining parameters
such as ‗ON‘ time, ‗OFF‘ time and current have been noticed.
Material removal rate calculation
A number of sparks are produced between the electrodes and every spark removes material
and a crater is formed. The crater under a single spark has been shown below. It is assumes a
hemispherical shape of radius ― r‖. The molten crater can be assumed to be hemispherical in
nature with a radius r which forms due to a single pulse or spark. Hence material removal in a
single spark can be expressed as
3
3
2
rVc 
Now material removal rate is the ratio of material removed in a single spark to cycle time.
offon
cc
tt
V
t
V
MRR



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The energy content of a single spark is given as
onVItE 
sparkoftimeont
sparkgleoftimet
craterofradiusr
movedrematerialofvolumeV
on
c




sin
Now it can be assumed that material removal in a single spark would be proportional to the spark
energy.
EVc
Heat Affected Zone
In EDM, with the temperature of the discharges reaching 8000 to 12,000°C, metallurgical
changes occur in the surface layer of the work piece. Due to the extremely-high temperature of
the spark in the EDM process, a heat-affected zone, or HAZ is produced. The work piece material
melted by the discharge is not fully expelled into the dielectric.
There are two thermally affected sub-layers of material: the recast layer or white layer and the heat
affected zone.
1. Re-cast or ―white layer‖: A white recast layer: This is the material that has melted and
rapidly solidified(, rapidly quenched by the dielectric fluid) and is not flushed away
by the electric fluid, subsequently producing an extremely brittle surface.
2. Heat-affected zone (HAZ), or annealed layer, which has only been heated, not melted.
The heat affected zone retains the metallurgical structure of the parent material as the
temperature absorbed is not to the level to change the structure.
3. Below the heat affected zone is the parent material and this area is unaffected by the
EDM process.

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Wire cut electric discharge machining (WEDM)
This is a special type of electric discharge machining that uses a small diameter wire as a
cutting tool on the work. Process details of WEDM are almost similar to EDM with slight
difference.
The tool used in WEDM process is a small diameter wire as the electrode to cut narrow kerf
in the workpiece. During the process of cutting the wire is continuously advanced between a
supply spool and wire collector. Material of wire can be brass, copper, tungsten or any other
suitable material to make EDM tool. Normally, wire diameter ranges from 0.076 to 0.30 mm
depending upon the width of kerf. (notice the meaning of kerf from the figure). Like EDM
process dielectric fluid is continuously sprayed to the machining zone. This fluid is applied by nozzles
directed at the tool work interface or workpiece is submerged in the dielectric fluid container.
Advantages
1. Accuracy and precision of dimensions are of very good quality.
2. No force is experienced by the workpiece. It does not impose any force to workpiece so
used for very delicated and thin workpieces
3. Hardness and toughness of workpiece do not create problems in machining operation
4. Efficient Production Capabilities - Because of the precision and high-speed of wire
EDM machines, many parts can be more economically produced with wire EDM,
rather than with conventional machining.(gears, cams and dies etc)
Disadvantages and Limitations of WEDM
1. The major disadvantages of this process are that only electrically conducting materials
can be machined. This process is costly so recommended for use specifically at
limited operations.
Differences between EDM and ECM
ECM EDM
Medium Electrolyte Dielectric
Removal mechanism Removal Chemical action removal by melting
Tool wear No tool wears tool wear
Removal rate High MRR Low MRR
Dimensional accuracy Low High
Surface finish High Low
HAZ Less High

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Electron Beam Machining (EBM)
EBM is a metal removal process by a high velocity focused stream of electrons. As the
electrons strike the workpiece with high velocity, their kinetic energy is transformed into
thermal energy which melts and vaporizes the material. The production of free electrons
(negatively charged particles) are obtained by electron gun. Due to pattern of electrostatic
field produced by grid cup, electrons are focused and made to flow in the form of a
converging beam through anode. The electrons are accelerated while passing through the
anode by applying high voltage at anode. A magnetic deflection coil is used to make electron
beam circular and to focus electron beam at a point (localized heating). The process is carried
out in a vacuum chamber to prevent electrons from colliding with molecules of the
atmospheric air and to prevent tungsten filament from getting oxidizing with air
AdvantagesofEBM
1. There is no mechanical contact between too landworkpiece,hencenotoolwear.
2. Very small holes can be machined in every type of material with high accuracy
3. Drilling holes with high depth/diameter ratios, greater than 100:1
4. A wide range of materials like steel, stainless steel, Ti and Ni super-alloys, aluminium
as well as plastics, ceramics can be machined successfully using electron beam.
5. EBM does not apply any cutting force on the workpieces. Thus very simple work
holding is required. This enables machining of fragile and brittle materials by EBM.
DisadvantagesofEBM
1. Costofequipmentishigh.
2. Rateofmaterialremovalislow.
3. Itcanbeusedforsmallcutsonly.
4. Vacuumrequirementslimitsthesizeofwork piece.
Application of EBM
1. Drillingofholesinpressuredifferentialdevicesusedinnuclearreactors,aircraftengine
2. Machiningofwiredrawingdieshavingsmall cross sectional area

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Laser Beam Machining (LBM)
Laser beam machining (LBM) uses the light energy from a laser to remove material by
vaporization and ablation. Laser beam melts the material by focusing a coherent beam of
monochromatic light on the work-piece. The light produced by the laser has significantly less
power than a normal white light, but it can be highly focused, thus delivering a significantly
higher light intensity and respectively temperature in a very localized area.
The LBM process does not involve mass material removal, but does provide rapid material removal
with an easily controlled, non-contact, non wearing tool.
Cooling Mechanism: to avoid its overheating in long continuous operation.
Tool Feed Mechanism
Focusing laser beam (cutting tool) at a pre-decided point in the workpiece serves as the tool.
The movement of the converging lens to shift the focussing is the tool feed mechanism in
LBM process.
 Mirrors direct the beam from the source down to the lens
 The lens then focuses the beam into the desired geometry

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Advantages of LBM
1. Materials which cannot be machined by conventional methods are machined by
LBM (ceramics, glass to softer materials like plastics, rubber wood).
2. There is no tool so no tool wear.
3. Application of heat is very much focused so rest of the workpiece is least affected
by the heat.
4. Drills very find and precise holes and cavities.
Disadvantages of LBM
1. High capital investment is involved. Operating cost is also high.
2. Recommended for some specific operations only as production rate is very slow.
3. Cannot be used comfortably for high heat conductivity materials light reflecting
materials.
4. Skilled operators are required.
Applications of LBM
 LBM is used to perform different machining operations like drilling, slitting, slotting,
scribing operations. It is used for drilling holes of small diameter of the order of 0.025
mm. It is used for very thin stocks. Other applications are listed below :
 Making complex profiles in thin and hard materials like integrated circuits and printed
circuit boards (PCBS).
 Machining of mechanical components of watches.
 Smaller machining of very hard material parts.
Ion beam machining
In IBM, a stream of charged atoms (ions) of an inert gas, such as argon, is accelerated in a
vacuum by high energies and directed toward a solid workpiece. The beam removes atoms
from the workpiece by transferring energy and momentum to atoms on the surface of the
object. When an atom strikes a cluster of atoms on the workpiece, it dislodges between 0.1
and 10 atoms from the workpiece material.
 superheated stream of electrically ionized gas to melt and remove material
 The process can be used on almost any conductive material

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Ion beam machining (IBM) takes place in a vacuum chamber using charged ions fired from
an ion source toward the workpiece by means of an accelerating voltage. The mechanism of
material removal in IBM differs from that of EBM. It is closely related to the ejection of
atoms, from the surface, by other ionized atoms (ions) that bombard the work material. The
process is, therefore, called ion etching, ion milling, or ion polishing.
A heated tungsten filament acts as the cathode, from which electrons are accelerated by
means of high voltage (1 kV) toward the anode. During the passage of these electrons from
the cathode toward the anode, they interact with argon atoms in the plasma source, to produce
argon ions.
Ar +e−
→Ar+
+ 2e
Advantages of IBM
1. Low temperature processing reduces handling an stress problems.
2. No dimensional changes
3. Good adhesion of treated surface
4. Can improve corrosion, oxidation, wear, hardness, friction, fatigue
Disadvantages of IBM
1. Very shallow treatment (< 1 μm)
2. High cost
3. The surface can be weakened by radiation effects
Ion beam machine consists of
 A plasma souce generates ions
 Extraction grid for removing the ions from the plasma
 Specimen holding table
Ultrasonic machining (USM)
In Ultrasonic Machining, the tip of the tool vibrates at low amplitude and at high frequency in
an abrasive slurry. This vibration transmits a high velocity to fine abrasive grains between
tool and the surface of the work piece. Material removed by erosion with these abrasive
particles.
In ultrasonic machining, a tool of desired shape vibrates at an ultrasonic frequency (19 ~ 25
kHz) with an amplitude of around 15 – 50 μm over the workpiece. Generally the tool is
pressed downward with a feed force, F. Between the tool and workpiece, the machining zone
is flooded with hard abrasive particles generally in the form of water based slurry. As the tool
vibrates over the workpiece, the abrasive particles act as the indenters and indent both the
work material and the tool. The abrasive particles as they indent the work piece, material get

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removed. USM is mainly used for machining brittle materials {which are poor conductors of
electricity and thus cannot be processed by Electrochemical and Electro-discharge machining
The typical elements of an USM are
 Slurry delivery and return system
 Feed mechanism to provide a downward feed force on the tool during machining
 The transducer, which generates the ultrasonic vibration
 The horn or concentrator, which mechanically amplifies the vibration to the required
amplitude of 15 – 50 μm and accommodates the tool at its tip.
High power sine wave generator
This unit converts low frequency (60 Hz) electrical power to high frequency (20kHz)
electrical power.
Transducer
The ultrasonic vibrations are produced by the transducer. Essentially transducer converts
electrical energy to mechanical vibration. The transducer for USM works on the following
principle
 Piezoelectric effect
 Magnetostrictive effect
 Electrostrictive effect
Piezo electric transducer: These transducer generate a small electric current when they are
compressed. Also when the electric current is passed though crystal it expands. When the
current is removed, crystal attains its original size and shape. Piezo electric crystals have high
conversion efficiency of 95%.
Magneto-strictive transducer: is a property of ferromagnetic materials that causes them to
change their shape or dimensions during the process of magnetization. These transducer are made
of nickel, nickel alloy sheets. The maximum change in length can be achieved is about 25
microns.

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Tool holder or Horn or concentrator
The tool holder holds and connects the tool to the transducer. The concentrator is usually a
cylindrically shaped metal rod which amplifies and concentrates the vibration to the tool from
the transducer. The device is necessary because the amplitudes provided by the transducers
themselves are insufficient for most practical applications of power ultrasound
Cutting Tool
Tool of USM vibrates with small amplitude at high frequency to vibrate abrasive slurry to cut
the work-piece material. The tool is attached to the arbor (tool holder) by brazing or
mechanical means. . The tool is made of relatively soft material.
Feed Mechanism
Tool is fed to the machining zone of workpiece. The tool is shaped as same to the cavity of be
produced into the workpiece. The tool is fed to the machining area. The feed rate is
maintained equal to the rate of enlargement of the cavity to be produced.
Advantages of USM
1. Its main advantage is the workpiece after machining is free from any residual
stress as to concentrated force or heat is subject to it during the machining
process.
2. Extremely hard and brittle materials can be machined, their machining is very
difficult by conventional methods.
3. Very good dimensional accuracy and surface finish can be obtained.
4. Operational cost is low.
5. The process is environmental friendly as it is noiseless and no chemical and
heating is used.
Disadvantages of USM
1. Its metal removal rate (MRR) is very low and it can not be used for large
machining cavities.
2. Its initial setup cost and cost of tool is very high, frequency tool replacement is
required as tool wear takes place in this operation.

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3. Not recommended for soft and ductile material due to their ductility.
4. Power consumption is quite high.
5. Slurry may have to be replaced frequently.
Applications
 Used for machining hard and brittle metallic alloys, semiconductors, glass, ceramics,
carbides etc.
 Used for machining round, square, irregular shaped holes and surface impressions.
 Machining, wire drawing, punching or small blanking dies.
Process Parameters and their Effects
The main process parameters which govern the ultrasonic machining process is as follows
 Amplitude of vibration (ao ) – 15 – 50 μm
 Frequency of vibration (f) – 19 – 25 kHz
 Feed pressure (p)
 Abrasive size – 15 μm – 150 μm
 Abrasive material – Al2O3-SiC -B4C -Boronsilicarbide -Diamond
 Volume concentration of abrasive in water slurry – C

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Abrasive Jet machining (AJM)
In abrasive jet machining, a focused stream of abrasive particles, carried by high pressure air
or gas is made to impinge on the work surface through a nozzle and the work material is
made to impinge on the work surface through a nozzle and work material is removed by
erosion by high velocity abrasive particles. The selection of abrasive particles depends on the
hadness and Metal Removal Rate (MRR) of the workpiece. Most commonly, aluminium
oxide or silicon carbide particles are used.
Working
Dry air or gas is filtered, compressed and regulated (pressure and flow rate) while passed into
the mixing chamber. In the mixing chamber, abrasive powder is fed and is thoroughly mixed
with air. The nozzle increases the velocity of the mixture at the expense of its pressure.
Nozzles direct abrasive jet in a controlled manner onto work material. The velocity of the
abrasive stream ejected through the nozzle is generally of the order of 330m/sec.
Advantages of Abrasive Jet Machining (process capabilities)
1. Surface of the workpiece is cleaned automatically.
2. Smooth surface finish can be obtained.
3. Equipment cost is low.
4. Hard materials and materials of high strength can be easily machined.
5. Narrow slot can be produced
Disadvantages of Abrasive Jet Machining (limitations)
 Metal removal rate is low
 In certain circumstances, abrasive particles might settle over the workpiece.
 Nozzle life is less. Nozzle should be maintained periodically.
 Abrasive Jet Machining cannot be used to machine soft materials.

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Process performance parameters
For AJM process, it is necessary to analyze the following process criteria.
1. Material removal rate
2. Geometry and surface finish of work piece
3. Wear rate of the nozzle
Performance generally influenced by the process parameters as enumerated below:
1. Abrasives used and its shape, size and composition
2. Carrier Gas properties (Density, pressure and velocity of carrier gas)
Density – 1.3 kg/m3
Velocity - 500 to 700 m/s
Pressure - 2 to 10 bar
3. Nozzle (material and diameter (0.2 to 0.8mm)
Effect of abrasive flow rate and grain size on MRR
It is clear from the figure that at a particular pressure MRR increase with increase of abrasive
flow rate and is influenced by size of abrasive particles. But after reaching optimum value,
MRR decreases with further increase of abrasive flow rate.
Stand off distance
Stand off distance is defined as the distance between the face of the nozzle and the work
surface of the work. SOD has been found to have considerable effect on the work material
and accuracy. A large SOD results in flaring of jet which leads to poor accuracy. It is clear
from figure that MRR increase with nozzle tip distance or Stand off distance up to certain
distance and then decreases. Decrease in SOD improves accuracy, decreases kerfwidth, and
reduces taper in machined groove.

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Applications
1. Used for cutting thin fragile components like germanium, silicon etc.
2. Most suitable for machining brittle and heat sensitive materials like glass, quartz,
sapphire, mica, ceramics germanium , silicon and gallium.
3. De-flashing small castings, engraving registration numbers on toughened glass used
for car windows
4. AJM is useful in manufacture of electronic devices , drilling of glass wafers, making
of nylon and Teflon parts permanent marking on rubber stencils, cutting titanium foils
Water jet machining and Abrasive Water Jet Machining (WJM/ AWJM)
Water jet machining
Water jet cutting uses the beam of water exiting the orifice to cut soft materials. The inlet
water is typically pressurised between 1300 – 4000 bars. Water jet cutting is mostly used to
cut lower strength materials such as wood, plastics and aluminium. This method is not
suitable for cutting hard materials.
Abrasive water jet machining (AWJM)
Abrasive water jet cutting is an extended version of water jet cutting; in which the water jet
contains abrasive particles such as silicon carbide or aluminium oxide in order to increase the
material removal rate above that of water jet machining. Almost any type of material ranging
from hard brittle materials such as ceramics, metals and glass to extremely soft materials such
as foam and rubbers can be cut by abrasive water jet cutting. Abrasive water jet cutting is
highly used in aerospace, automotive and electronics industries. The addition of abrasives to
the water jet enhanced MRR and cutting speeds (51 and 460 mm/min).

Page22
Advantages of abrasive water jet cutting
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.
Limitations of abrasive water jet cutting
 Cannot drill flat bottom
 Cannot cut materials that degrades quickly with moisture
 Surface finish degrades at higher cut
 High capital cost and high noise levels during operation.
Plasma arc machining (PAM)
It is also one of the thermal machining processes. Here the method of heat generation is
different than EDM. In this process gases are heated and charged to plasma state. Plasma
state is the superheated and electrically ionized gases at approximately 5000o
C. A high
velocity jet flow of hot ionized gas melts the metal and then removes the molten material to
form a kerf.
Plasma Gun
The plasma gun consists of a tungsten electrode fitted in the chamber. The electrode is given
negative polarity and nozzle of the gun is given positive polarity. Supply of gases is
maintained into the gun. A strong arc is established between the two terminals anode and
cathode. Gases are used to create plasma like, nitrogen, argon, hydrogen or mixture of these
gases. There is a collision between molecules of gas and electrons of the established arc. As
a result of this collision gas molecules get ionized and heat is evolved. This hot and ionized

Page23
gas called plasma is directed to the workpiece with high velocity. The established arc is
controlled by the supply rate of gases.
Power Supply and Terminals
Power supply (DC) is used to develop two terminals in the plasma gun. A tungsten electrode
is inserted to the gun and made cathode and nozzle of the gun is made anode. Heavy potential
difference is applied across the electrodes to develop plasma state of gases.
Cooling Mechanism
As we know that hot gases continuously comes out of nozzle so there are chances of its
overheating. A water jacket is used to surround the nozzle to avoid its overheating.
The metals usually cut with this process are the aluminium and stainless steels. The process
can also be used for cutting carbon steels, copper alloys, and nickel alloys
Advantages of PAM Process
 It gives faster production rate.
 Very hard and brittle metals can be machined.
 Small cavities can be machined with good dimensional accuracy.
Disadvantages of PAM Process
 Its initial cost is very high.
 The process requires over safety precautions which further enhance the initial cost
 Some of the workpiece materials are very much prone to metallurgical changes on
excessive heating so this fact imposes limitations to this process.
 It is uneconomical for bigger cavities to be machined.
Applications of PAM

Page24
 The chief application of this process is profile cutting as controlling movement of spray
focus point is easy in case of PAM process. This is also recommended for smaller
machining of difficult to machining materials.
Transferred and non transferred plasma arc machining
A plasma jet can be operated in the transferred mode, where the electric current flows
between the plasma torch electrode (cathode) and the workpiece (anode). It can also be
operated in the non-transferred mode where the electric current flows between the electrode
and the torch nozzle. Both modes of operation are illustrated in Figure. The quality of plasma
produced is a function of density (pressure), temperature and torch power (the greater the
better).
The Non-trasferred arc torch extends from the electrode or the cathode to the end of the
nozzle. The nozzle acts as the anode. This type of plasma jet is completely independent of the
work piece.
Transferred – In the transferred system the arc is completed by making contact with the
workpiece.
Non-transferred – In the non-transferred system the arc is completed by making contact with
nozzle, it can produce an arc without touching the grounded workpiece and can be very
dangerous
Rapid prototyping
The term rapid prototyping (RP) refers to a class of technologies that can automatically
construct physical models from Computer-Aided Design (CAD) data for the purpose of
testing the various design features, ideas, concepts, functionality, output and performance.
Rapid Prototyping technology employs various engineering, computer control and software
techniques directly to produce a physical model layer by layer (Layer Manufacturing) in
accordance with the geometrical data derived from a 3D CAD model.
 A virtual prototype (a CAD model of the part) may not be sufficient for the designer
to visualize the part adequately
 Using RP to make the prototype, the designer can see and feel the part and assess its
merits and shortcomings

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Conventional machining (turning, milling, drilling etc) can produce prototypes using metal
removal method until the desired shape is achieved, which are called subtractive processes.
Rapid Prototyping (RP) is an additive process, adds material in a layering process, to create
the desired form, thus enabling complex forms to be manufactured in one piece that would
otherwise be impossible.
Rapid Prototyping (RP), also known as Solid Freeform Fabrication (SFF) builds complex
shapes through additive processes, producing components without the use of tools.
The advantages of RP
1. Physical models of parts can be manufactured in a matter of hours and allow the rapid
evaluation of manufacturability and design effectiveness. In this way, rapid
prototyping serves as an important tool for visualialization and concept verification.
This helps the user in knowing how the final product will look like.
2. As the development costs are reduced, Rapid prototyping proves to be cost effective.
3. The process itself reduces waste, as unused materials can be recycled.
4. It is easier to find the design flaws in the early developmental stages.
5. There is better communication between the user and designer as the requirements and
expectations are expressed in the beginning itself.
6. High quality product is easily delivered by way of Rapid prototyping.
In short why use Rapid Prototyping
1. To increase effective communication.
2. To decrease development time.
3. To decrease costly mistakes.
4. To minimize sustaining engineering changes.
5. To extend product lifetime by adding or eliminating features early in the design.
All RP techniques employ the same basic five-step process.
Starting with CAD file of the object, software divides the object into a series of thin slices,
stacked on top of one another. Using this data, commercial Rapid Prototyping machines
slowly and precisely add material, recreating the individual layers and ultimately the
component.

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1. Create a 3D CAD model of the design
2. Convert the CAD model to STL format (Stereo lithography)
3. Slice the STL file into thin cross-sectional layers
4. Construct the model one layer atop another
5. Clean and finish the model
Types of Rapid Prototyping
While there are many ways in which one can classify the numerous RP systems one of the
better ways is to classify RP systems on the basis of the material that the prototype or part is
built with. In this manner, all RP systems can be easily categorized into
(1) Liquid-based
(2) Solid-based and
(3) Powder-based.
Liquid-based RP systems have the initial form of its material in liquid state. The
Stereolithography Apparatus (SLA) falls into this category.
Solid-based RP systems encompass all forms of material in the solid state. In this context, the
solid form can include the shape in the form of wire, roll, laminates, pellets and powders. The
Selective Laser Sintering (SLS), Three-Dimensional Printing (3DP) Fused Deposition
modeling (FDM) fall into this definition
Another classification of Rapid prototyping into following groups
 Subtractive ( Removal of material )
Conventional methods of prototyping (by machining or other process0
 Additive (adding of material): Build parts in layer by layer (slice by slice as stacking a
loaf of bread)
o Stereolithography
o Fused Deposition Modeling (FDM)
o Selective Laser Sintering (SLS)
o Laminated Object Manufacturing
Stereolithography (SLA)
Stereo-lithography is one of the most common types of Rapid Prototyping processes. Stereo-
lithography Apparatus (SLA) technology fabricates three-dimensional solid objects from
liquid resin. It is a material additive manufacturing process. A computer controlled UV laser
draws the image of the object on the surface of liquid plastic. The laser takes passes at hitting

Page27
the liquid plastic and thereby hardening it. At the completion of each pass, the object would
be lowered so that the UV laser could go through its next pass. This process continues and the
end result is a carved out 3-D physical model of the object.
Laser– concentrative UV beam to transom
liquid resin into solid state
Elevator– control the movement of
platform upward
Platform– for the basement of part
building
Resin vat– contain raw material to form
SLA model
In SLA process, the software firstly interprets the CAD data and slices it into a series of thin
horizontal layers and converted to machine specified control data files based on the part. The
machine control data is then downloaded into the equipment for part building. A perforated
stainless steel building platform attached to a vertical elevator is moved to the start position
which is just below the resin surface. An X-Y electronic motor driver optical scanning
mirrors directs the laser beam, which cures the borders and cross sections of the built parts
one layer at a time on the surface of the resin. Photopolymers are converted into solid state
instantly after irradiation of laser beam. The elevator then lowers the newly built layer by a
distance of one layer thickness after a short period of time to allow the newly formed layer to
increase the green strength. The process is repeated until the object is completed and object is
taken out by raising the elevator and object is removed from the vat.
Advantages
1. Stereolithography is one of the most used forms of rapid prototyping because of
accuracy (Tolerances= 0.0125mm)
2. Less time taken (depends upon the size and complication of the part)
3. Wide shape and complex geometries can made
4. Pattern for all casting and moulding can be made economically
Disadvantages
1. Expensive
2. Size of object (50*50*60 cm) is limited
Applications
1. Medical and Health care parts
2. Electronics; Packaging, Connectors
3. Casting Patterns and Jigs and Fixtures
4. To test design Appearance and evaluation of Models
5. Wind-Tunnel Test Models etc
Fused Deposition Modeling (FDM)
Fused deposition modeling is also a rapid prototype technology commonly used to convert
CAD drawings into physical parts. FDM works on an "additive" principle which extrudes
material in layers. Plastic or wax is melted and liquefied in the extrusion head and extruded
through a nozzle. The nozzle is made to move over a trail identified by the CAD design to

Page28
produce part. This way single layer is extruded and then it is dropped to extrude the next
layer on top of the first until the entire prototype is built, with one layer at a time. Upon
hitting the build platform, the liquid solidifies and the platform lowers where the next layer of
liquid is laid upon it. This process continues until the product is complete.
Advantages
1. FDM process part can be high strength, it is cost-effective and waterproof.
2. Easy material change
3. Thin parts can be made
4. Tolerance of +/- 0.005‖
5. Low temperature operation
Disadvantages
1. Part strength is weak perpendicular to build axis
2. Seam line between layers
3. Temperature fluctuation during production lead to de-lamination
4. Support requirement is difficult
Application
Used for making concept and functional models in many industries.
 Concept models — Test form and fit, communicate design intent
 Functional prototypes — Tough prototypes that can be used for functional tests
Typical applications include automotive, aerospace or any application where your part needs
to be functionally tested in an environment of heat or chemicals.
Selective Laser Sintering (SLS)
Selective Laser Sintering uses the principle of sintering. Sintering is a heating process that
prevents melting and a coherent mass is produce. In SLS, metallic or non-metallic powders
are sintered using a CAD program guided laser that selectively fuses the powdered material.
It works with a high powered laser – as the laser selectively moves over the surface of

Page29
thermoplastic powder it fuses cross-sections of the material layer by layer. As one layer is
completed, the process is repeated by lowering the powdered bed and adding a fresh layer of
material.
First cylinder moves up so that a layer of material can be send to the second cylinder. In
second cylinder after recieving a layer of material, it is processed using laser beam. Then
second cylinder moves down to receive the next layer from the first cylinder as it moves up to
supply the next layer of materials. The processes continue till final product forms.
Advantages
1. SLS offers the freedom to quickly build complex parts that are more durable and
provide better functionality over other rapid prototyping technologies.
2. Fabricated prototypes are porous (typically 60% of the density of molded parts) thus
impairing their strength and surface finish.
3. Fast build times
4. Variety of materials can be processed
Disadvantages/ Limitations
1. Typical SLS parts have little rough & porous surface finish which is not as smooth as
SLA
2. The larger shrink rates of SLS increase the tendency for the prototype to warp, bow or
curl subject to the part geometry.
3. Material changeover difficult compared to FDM & SLA.
4. Some post-processing / finishing required
Laminated Object Manufacturing (LOM)
In it, layers of adhesive-coated paper, plastic, or metal laminates are successively glued
together and cut to shape with a knife or laser cutter. The main components of the system are
a feed mechanism that advances a sheet over a build platform, a heated roller to apply

Page30
pressure to bond the sheet to the layer below, and a laser to cut the outline of the part in each
sheet layer. Parts are produced by stacking, bonding, and cutting layers of adhesive-coated
sheet material on top of the previous one. A laser cuts the outline of the part into each layer.
After each cut is completed, the platform lowers by a depth equal to the sheet thickness and
another sheet is advanced on top of the previously deposited layers. The platform then rises
slightly and the heated roller applies pressure to bond the new layer. The laser cuts the outline
and the process is repeated until the part is completed. After a layer is cut, the extra material
remains in place to support the part during build.
The process is performed as follows:
1. Sheet is adhered to a substrate with a heated roller.
2. Laser traces desired dimensions of prototype.
3. Laser cross hatches non-part area to facilitate waste removal.
4. Platform with completed layer moves down out of the way.
5. Fresh sheet of material is rolled into position.
6. Platform moves up into position to receive next layer.
7. The process is repeated.
Advantages
1. Dimensional accuracy is slightly less than that of stereolithography and selective laser
sintering but no milling step is necessary.
2. Relatively large parts may be made, because no chemical reaction is necessary
3. Low cost due to readily available raw material
Laser engineered net shaping (LENS)
This process is similar to other rapid prototyping technologies in its approach to fabricate a
solid component by layer additive methods. The laser creates a molten pool of metal on the
substrate, into which powder feeder injects powders into the melt pool. The metal powder
rapidly solidifies forming lines of deposited material on the substrate. Lines are sequentially
deposited adjacent to one another until an entire layer is fabricated. The laser focal point is
then moved in the positive Z direction to begin depositing the next layer. An inert gas is used
to shield the metal from atmospheric gases. It uses a layered approach to manufacture the
components. Process principle; local melting of metal powders using a laser

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Advantages
1. Can be used to repair parts as well as fabricate new ones
2. The properties of the material are similar or better than the natural materials
Disadvantages
1. Some post processing involved
2. Has a rough surface finish, may require machining or polishing
3. Low dimensional accuracy
Application
1. Fabrication and repair of injection molding tools
2. Fabrication of large titanium & other exotic metal parts for aerospace applications
3. Parts have been fabricated from stainless steel alloys, nickel-based alloys, tool steel
alloys, titanium alloys etc
Laser welding
Laser beam welding (LBW) is a welding technique used to join multiple pieces of metal
through the use of a laser. The beam provides a concentrated heat source, allowing for
narrow, deep welds and high welding rates. The process is frequently used in high volume
applications, such as in the automotive industry.
Advantages of LBW
1. Laser beam can be transmitted through air rather than requiring a vacuum,
2. The process is easily automated
3. LBW results in higher quality welds.

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Liga processes
The LIGA-process is used to manufacture micro structures by deep X-ray lithography. Using
the process, microstructures can be manufactured from different plastic materials and metals.
The LIGA consists of three main processing steps;
1. Lithography,
2. Electro-forming/electroplating
3. Molding.
Step involved
1. Apply resist and X-ray exposure through mask,
2. Remove exposed portions of resist,
3. Electrodeposition to fill openings in resist,
4. Strip resist for (a) mold or (b) metal part
In the process, an X-ray sensitive polymer photoresist, typically PMMA, (Poly methyl
methacrylate), a transparent thermoplastic bonded to an electrically conductive substrate, is
exposed to parallel beams of high-energy X-rays from a radiation source through a mask
partly covered with a strong X-ray absorbing material. Chemical removal of exposed (or
unexposed) photoresist results in a three-dimensional structure, which can be filled by the
electrodeposition of metal. The resist is chemically stripped away to produce a metallic mold
insert. The mold insert can be used to produce parts in polymers or ceramics through
injection molding.
Advantages
1. The primary advantage of LIGA process is its capability to make large aspect
ratio structures(can be up to 1000 μm thick while only several micron wide/large
height-to-width ratios in the fabricated part)
2. LIGA is a versatile process – it can produce parts by several different methods
3. Wide range of part sizes is feasible
4. Close tolerances are possible and highsurface finish.
5. High production is possible

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Disadvantages
 X-ray LIGA is expensive due to the equipment required.
 Slow process.
 Complicated process.
 Difficulty transitioning from research to production.
Applications
 MEMS Components
 Sensors
 Actuators
 Trajectory Sensing Devices
 Mass Spectrometers
 Microoptical Components
 Components such as micro lenses, mirrors, and filters
 benefit from low surface roughness to reduce scattering.

Page34
Module V---Question
1. Briefly explain non-transitional machining process. Give applications
2. Discuss the dimensional tolerance that can be achieved by unconventional machining.
3. What is the importance of non traditional machining?
4. How is chemical machining different from electrochemical machining?
5. Explain the influence of chemical machining as product tolerance and surface finish.
6. Draw the schematic arrangement of ECM. Explain its working and limitations.
7. Name any two electrolytes used in ECM process.
8. How will you differentiate the ECM with EDM process?
9. With a neat sketch, explain Electro-chemical Machining process. List the major
process and applications.
*****************************************************************
10. Explain EDM. What are its applications?(8 marks)
11. Compare the different tool materials used in spark EDM.
12. Explain the principle of Wire EDM. .
13. List out the advantages of EDM
14. Explain EDM. What are its applications?(8 marks)
15. Illustrate arid explain the process of EDM and state the differences in process
parameters used in wire cut EDM.
16. List out the advantages of EDM process. .
17. Discuss the EDM process.
18. List out its applications of `WEDM.
19. Explain the role of dielectric' in EDM process. (4 marks)
20. Discuss the various factors of EDM that affect
a. the metal removal rate and
b. the accuracy of holes obtained in EDM
21. Why has the wire EDM process become so widely accepted in industry.
22. Sketch and explain an Electro-discharge machining process. List the important
process variables and discuss their effects on MRR and surface finish.
23. Discuss the various factors that affect (i) the metal removal rate and (ii) the accuracy
of holes obtained in EDM.
24. What are the merits of EDM
25. Describe the selection of dielectric medium in EDM.
26. What are the capabilities of wire EDM? Could this process be used to make tapered
pieces? Explain.
*********************************************************
27. Explain the working of Electron Beam machining with the help of a neat diagram.
Discuss its application areas
28. Distinguish between laser beam machining and electron beam machining. Give their
field of application in the area of manufacturing.
29. Draw and explain the construction and working of the Electron Beam Illustrate the 4
steps leading to material removal by EBM and explain the process. (12 marks)

Page35
30. In Plasma Arc Machining, how a transferred is are processes different from a non-
transferred arc ―process?
31. What are the distances of electron beam over laser beam for machining?
32. List the different types of laser used in Laser beam machining. .
33. How is laser produced?
34. Briefly explain the working principle of LBM.
35. Describe the plasma are cutting and machining;
**************************************************************
36. What is meant by kerfwidth in AJM? How does it relate to the nozzle tip distance?
37. Illustrate and explain the Abrasive Water Jet Machining process and state the
advantages, limitations and applications of the process.
38. Draw graphs to relate the following process parameters to the material removal rate in
abrasive jet machining
a. Nozzle tip distance.
b. Abrasive flow rate.
c. Abrasive grain size
39. Discuss abrasive water jet machine.
40. List any two advantages of AJ M process.
41. Discuss any four process parameters involved in AJM.
42. List the various elements of AJM process and explain their influence on process
parameters.
43. Explain the process parameters which influence Metal Removal rate in Abrasive Jet
Machining
44. What are the limitations of abrasive jet machining
45. Describe, in detail, metal removal by abrasive jet machining.
*******************************************************
46. Why are abrasive slurry is used in ultrasonic machining? _
47. Sketch and explain Ultrasonic Machining.
48. Explain the principle of ultrasonic machining. What are the limitations of USM
49. Why is frequency tuning a must in Ultrasonic Machining?
50. What is the function of a concentrator in Ultrasonic Machining?
*********************************************************************
51. `What is rapid proto-typing?
52. Briefly explain the types, process and advantages of Rapid prototyping process.
53. Explain the fused deposition modelling and laminated object manufacturing methods
used in Prototyping process.
54. List out the any four advantages of Rapid. Prototyping.
55. What do you meant by Virtual and Physical prototyping?
56. Name the different types of Rapid prototyping.
57. Explain basic steps involved in Rapid prototyping with flow diagram.
58. What are the advantages of` rapid prototyping
59. What is Fused Disposition Modeling method of rapid prototyping

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60. What is stereo lithography?
61. Briefly explain sterio-lithograpy
62. With a neat sketch, explain the stereo lithography process.
63. Discuss stereo lithography.
64. Explain the stereo lithography process in Rapid Prototyping with suitable sketches.
65. What is the abbreviation for LIGA? What are the tolerances obtained in the LIGA
process?
66. Explain LIGA process.
67. Discuss briefly LIGA process and list out its applications.
68. Write short notes on Liga process.
**********************************************************************
69. What are the advantages of hydraulic forming?
70. Describe, briefly hydro forming
71. Explain the process of electro hydraulic forming and give its salient characteristics.
72. Describe with neat the sketch the principle of operation and equipment required for
Electro hydraulic forming
73. Sketch and explain an Electro hydraulic forming process.
74. Explain Electro-hydraulic forming with the help of a neat sketch.
75. Sketch and explain the explosive forming methods to produce a bulge and a cavity in
a cylindrical part
76. Differentiate between contact and non-contact explosive forming.
77. Mention some of the uses of explosive forming.
78. Write short notes on application of explosive forming.
79. Sketch a few shapes of some parts that are formed by explosive forming.
80. Describe, with suitable sketches, the explosive forming.
81. Define the tern explosive forming.
82. What are the advantages and limitations of explosive forming?
83. Name two distinctive advantages and limitations of explosive forming. Briefly
explain how it is performed.
84. Explain the process of electro-magnetic forming and give its salient characteristics.
85. What is the principle of Electromagnetic forming?
86. Describe, with suitable sketches, echo-magnetic forming.
87. What is the principle of electro-magnetic forming? What are its advantages? State a
few applications of this process.
88. Explain the principle of magnetic pulse forming with neat sketch. What are the major
constraints of this process?
89. What is the principle of Magnetic Pulse Forming?
90. Write down about 3D-welding.
91. List the merits of High Energy Rate Forming.

Page37
Extra
Area of application of various non conventional processes
Chemical machining (CM): Chemical milling is usually applied where larger quantities of
material is to be removed from large plates or panels in the aircraft industry, space industry or
cutting in depths of up to 12 mm. The process is used to make large aluminium alloy, etc.
plates and sheet-metal parts lighter. Chemical blanking is used for manufacturing various
scales, dials, rulers, etc. in the instrument-making industry and fine mechanical engineering
industry as well as for manufacturing a variety of thin component parts in the mechanical
engineering industry. The photo-chemical blanking is applied for manufacturing printed
circuit boards for the electronic industry, electrical wiring, electronic chip sets and very thin
component parts (depths of up to 0.0025 mm) for the aero-space industry, optics,
microelectronics, instrument -making industry, printing industry, crafts – engraving metal or
other material articles.
b) Electrochemical machining (ECM): This is used in wide machining applications for
high-alloyed rigid steels and materials and also for manufacturing complex cutting shapes –
turbine propellers, tools – stamps, moulds, dies. The technique is suitable for drilling small
holes and cutting into hard materials

Page38
c) Electrochemical grinding (ECG): The technique is applied in machining carbide tools
and alloy tools, carbide steel parts, etc. alloys featuring high strength characteristics. Used for
grinding, milling and drilling small holes. Not suitable for manufacturing dies
d)Electrical discharge machining (EDM): The technique is applied for manufacturing tools
and dies – for machining cavities and contour shaping and cutting. Used to cut and machine
very hard and hardened conductor materials. Used to manufacture complex dies, for example
for extrusion of aluminium component parts, etc.
e)Wire electrical discharge machining (WEDM): Used for contour cutting of flat or curved
surfaces The depth of the cutting plates is adjustable to up to 300mm. Mostly used for
grinding hard carbide alloys of titanium, tungsten etc and for machining fragile and brittle
small-size components, surgical tools, optical devices etc.
f)Laser-beam machining (LBM) is used for cutting, drilling, marking and for surface
machining and welding operations involving various materials: metals, ceramics, plastics,
leather, textiles, composite materials (in the aircraft industry, etc.).
g)Electron-beam (plasma) machining (EBM) is used in similar applications to those
described for LBM but performed in a vacuum surrounding medium: precise cutting and
welding of various materials.
h)Water-jet machining (WJM): This technique is used for dynamic cutting and machining
various materials: plastic, rubber, foodstuffs, paper, leather, insulation materials, composite
materials of up to 25mm thickness. Finds application in the food industry and the production
of plastics
j)Abrasive jet (gas) machining (AJM): Applied for machining small holes, cleaning surfaces
from removing sand or scale in foundry applications, stamped forgings and also for non-
metal and fragile materials, as well as for deburring operations.
Dielectric fluid in EDM
Fluids with high dielectric strength need lower time for the recovery of dielectric strength.
Thus, low pulse -off times are sufficient. This not only improves the MRR but also provides
better cutting efficiency because of a reduced probability of arcing. Liquids with low
viscosity generally provide better accuracies because of a better flow ability of the oil leading
to improved flushing. Dielectric fluids with high thermal conductivity and thermal heat
capacity can easily carry away excess heat from the discharge spot and lead to a lower
thermal damage.
Electrodes properties used in EDM
 Electrical Conductivity: higher conductivity (or conversely, lower resistivity) promotes
more efficient cutting.
 Melting Point: Since EDM is a thermal process, the higher the melting point of the
electrode material, the better the wear ratio between electrode and workpiece.
 Mechanical Properties – strength and hardness etc should be high
 Manufacturability: electrode shape should be easy to fabricate
 Cost- low

Page39
Various EDM electrodes
 Brass: Brass was one of the first EDM electrode materials. It is inexpensive and easy
to machine. Not in use due to its high wear rate.
 Copper: Copper electrode is conventional using for EDM process on its merits of
highly conductive, low cost, low wear ratio, good machinability, high finishing.
 Tungsten: Due to the combination of its high density, tensile strength, and
highmelting point, tungsten had been the electrode material of choice for certain
limited EDM applications. But cuts much slower than Brass or Copper due its poor
electrical conductivity
 Graphite Electrodes: Graphite is the preferred electrode material for EDM
applications.
o Graphite is faster than Copper in both roughing and finishing (machinability)
o Graphite usually wears less than Copper.
o Gives better Surface Finish:
 Copper Tungsten
 Copper graphite etc
Performance of EDM processes is highly influenced on processes parameters given below
 Discharge current (current Ip)
Discharge current is directly proportional to the Material removal rate. As current
density increases, the MRR is also increased and surface finish reduces.
 Spark On - time (pulse time or Ton)
The duration of time (μs) the current is allowed to flow per cycle. Material removal is
directly proportional to the amount of energy applied during this on -time. This
energy is really controlled by the peak current and the length of the on - time.
 Spark Off-time (pause time or Toff)
The duration of time (μs) between the sparks (that is to say, off -time). This time
allows the molten material to solidify and to be wash out of the arc gap. This
parameter is to affect the speed and the stability of the cut. Thus, if the off -time is too
short, it will cause sparks to be unstable.
 Arc gap (or gap):
The Arc gap is distance between the electrode and work piece during the process of
EDM. It may be called as spark gap.
 Voltage (V):
It is a potential that can be measure by volt it is also effect to the material removal rate
Comparison to other machining processes
Comparison with EDM
 Extremely precise parts are possible [±0.0001" (±0.025mm)]
 Very thick parts [over 12" (30 cm)] can be made
 Intentional taper can be put into a part for die clearance and other uses
Comparing abrasive jet to laser
 Very fast production in thin, non-reflective materials such as sheet steel.
 Accuracy to ±0.001" (±0.025 mm) or better in thin material.

Page40
Kerf
Like other jet cutting technologies, AWJM also produce kerfs which have some distinct
features and the quality of the kerf determines the quality of the work. Generally a kerf is
produced with a wider at the entrance of the jet and reduces at the bottom which is called a
kerf taper. Kerf geometry plays an important in determining the work quality as the kerf
produced has some taper angle, which is wider at the top and narrow at the bottom.
Virtual prototyping
Virtual prototyping involves using computer-aided design (CAD) and computer-aided
engineering (CAE) software to validate a design before committing to making a physical
prototype. This is done by creating (usually 3D) computer generated geometrical shapes
(parts) and either combining them into an "assembly" and testing different mechanical
motions, fit and function or just aesthetic appeal. Physical and virtual prototypes are not
competitive technologies. They are complementary. The strengths and advantage of one
technology will address the weaknesses and limitations of the other.
Forming methods (high energy forming)
In these forming processes large amount of energy is applied for a very short interval of time.
Many metals tend to deform more readily under extra – fast application of load which make
these processes useful to form large size parts. Hydroforming is a specialized type of die
forming that uses a high pressure hydraulic fluid to press room temperature working material
into a die.
Different types of metal forming operations are used. During electrohydraulic forming
stored electric energy is suddenly discharged through a spark gap so that the surrounding
working medium (e.g. water) is ionized and vaporizes, initiating a shockwave.
Electro Magnetic Forming: This process utilizes the energy of the magnetic field to deform
the metal.

Page41
Taper-cutting: Wire electric discharge machining method can be used for taper cutting by
directly programming the cut contour of the upper and lower surfaces of the workpiece.
Standard taper capability is up to 30 degrees
Industry importance of WEDM (Application)
1. Many parts can be economically produced with wire EDM, such as: precision gages
and templates, keyways, shaft and collet slots, gears, internal splines, cams, punches
and dies from one piece of tool steel
2. To cut intricate parts for aerospace and electrical industry
3. It is used to make narrow kerf with sharp corners.

Page42
EDM process voltage and current variation during a cycle

NON TRADITIONAL MACHINING & MATERIAL ADDITION PROCESS ( as per MGU syllabus)

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