Non conventional machining process

Comparison between Conventional and Non-conventional
machining :
Sr.
No
Conventional Non-Conventional
Direct contact of tool and
workpiece.
Tools are non-conventional technique
like Laser beam, electric arc etc.
1
Cutting tool is always harder than
w/p.
Tool may not be harder and it may not
be physical presence.
2
3 Tool life is less due to high wear. Tool life is more.
Generally Macroscopic chip
formation.
Material removal occur with or without
chip formation .
4
It uses different energy like electrical,
Thermo-Chemical etc. to provide
machining.
Material removal takes place due to
application of cutting force.
5
6 Suitable for all material Not suitable for all material.
It cannot be used to make prototype
parts very effectively.
It can be used to produce prototype
parts very effectively.
7

Electrical Discharge Machining
or
Spark Erosion
or
Spark machining
or Thermal
Erosion or
Electro Erosion Process

control gap
Filter Dielectric
Too
l
feed
,
Too
l
Spark
dischar
ge
m•
gap
Principle of EDM:
Servo
to
I

 The main attraction of EDM over conventional machining is that
erode undesiredthis technique use thermoelectric process to
material from the w/p.
Construction :
 System consist of Shaped tool, Power supply source, Dielectric
fluid and its circulation line, Servo controlled tool
and work.
feed mechanism



Tool
Work
Terminals
Cathode ( Negative terminal)
Anode ( Positive terminal)
are connected to DC power supply to create potential
difference between work and tool.
Distance between work and tool is known as Spark gap and it is
filled by dielectric fluid.


Working:
High voltage is applied between terminals and it induce electrical field in
spark gap.
Free electrons on tool are subjected to electrostatic force and hence they
are emitted from tool and accelerate towards work. There would be
collision between electrons and molecules in dielectric. It cause further
generation of electrons because of ionization of dielectric molecules.
This cyclic process increase concentration of electrons in spark gap and
when potential difference is sufficiently high dielectric break down and
large no. of electrons will flow from tool to job and ions from job to tool.
This movement of electrons visually seen as Spark and electrical energy is
dissipated as thermal energy of spark.
With a very short duration of spark , temperature of electrodes raised
locally to more than their normal boiling point and this heat of spark melt
a tiny bit of metal from work.
The melted metals cools and solidifies as tiny particles in dielectric .
The metal is carried away due to circulation of dielectric by means of
pump and the process continues.








Process Parameter:
Voltage: 40 to 300 V
Current: 0.5 to 400 A
Spark gap: 0.0125 to0.125 mm
Pulse duration: 2 to 2000 microsecond
MRR: 800 mm3 – 5000 mm3
Application of EDM:
 EDM Drilling to drill very
complex shapes.
small holes and EDM milling to machine
 EDM can be used to make parts with irregular shape with precision
for forging press tool, extrusion dies, cutting tool dies etc.

 Wire EDM use Electro thermal mechanism to cut electrically conductive
materials.
Construction:
 EDM consist NC unit to control counter movement of work, wire feeding
mechanism to move wire at constant tension, power supply and
dielectric fluid supply.
Wire of 0.02 to 0.3 mm



diameter
Tool
Work
Dielectric
Cathode (Negative terminal)
Anode ( Positive terminal)
is de-ionized water applied as localized steam rather than
submerging the whole work.
Wire for EDM is made of Brass, copper, tungsten, and Zinc or brass
coated wire. The wire should have high tensile strength and good
electrical conductivity.

Working:
 During operation wire moves along prescribed path and remove
material from work.
Same as EDM process material is removed due to series of discrete
discharge between Anode and Cathode in presence of dielectric fluid.
The place of discharge heated to extremely high temperature and that
surface is melted and material removed.
Removed particles flushed away by flowing dielectric fluids.




Advantage of Wire cut EDM:




Smooth machine surface and polishing not required.
Forming electrode to product shape is not required.
Wear of electrode is negligible.
Production rate is high machine can be easily operated for long time.
Application of Wire cut EDM:



Intricate components for electrical and Aerospace industries.
Machining of sheet metal die, extrusion dies and prototype parts.
Cylindrical objects are cut with high precision.

Laser beam machining (LBM)
It is thermal metal removal process which uses LASER
beam to melt and vaporize particles on the surface of
metallic and non-metallic work-pieces.

Construction:
 It consist cylindrical crystal ruby tube, flash tube, focusing lens, power
supply source, total and partial reflecting mirror and cooling system.
Ruby is Aluminum oxide with 0.05% Cr dispersed and it’s one end is
blocked with total reflective mirror while other end having partially
reflected mirror.
Flash tube is placed outside ruby crystal.



Working:
 Capacitor bank is charged by high voltage energy supplied which energize
flash tube by trigging system.
Flash tube flashes white light and Cr atoms in ruby crystal absorb this
energy and get excited.
This atoms pumped to high energy level and drop back to original state.
When atoms jump from one to another level it emits photons (Red


fluorescent light).
stimulation effect.
This phenomenon is known as lasing action or
 Due to reflection this effect is enhanced and finally photons will come
out from partially reflected mirror with great intensity called LASER.
Laser beam is focused with the help of lens and work is placed near focal
point of lens. Due to high temperature work material will melt and
vaporize.

 Ruby rod becomes high efficient at low temperature. Thus it is
continuous cooled with water or liquid Nitrogen.

LBM Process parameters:




Voltage: 4500 V
Pulse duration: 100 microsecond
MRR: 0.1 mm3/min
Surface Finish: 0.5-1.2 m (CLA)
APPLICATION of LBM:



LASER
LASER
LASER
drilling
metal cutting
welding

ADVANTAGE of LBM:





Small, complex and micro sized holes.
No direct contact between tool and work.
Accuracy is high and doesn’t require filler material.
Dissimilar material can easily welded.
Automated easily.
DISADVANTAGE:




It can’t be used to drill deep holes.
Highly reflective material can’t be effectively
Initial investment is high.
machined.
Safety must be followed strictly and skilled operator required.

Electron Beam Machining ( EBM )

EBM is thermo Electrical process in which material is removed by
high velocity electron beam emitted from tungsten filament. Kinetic
energy of beam transferred to work, producing heat and melt or vaporize
material locally.

Construction:
 It consist of vacuum chamber, electron gun, magnetic lens to focus beam,
deflecting coil, and work table for holding.
 Electron gun consist of grid cup, tungsten filament( cathode), Anode. The
filament and anode are connected with DC power supply.
Working:
 The tungsten filament is heated about 2500-3000 C by high voltage DC
supply in order to emit electrons. Grid cup direct electrons to travel towards
the work.
Electrons are attracted by the Anode ,and passed through already placed
hole without colliding with it.
Due to high potential difference electrons accelerated and it’s velocity
reaches near 2/3 of light velocity.
Electron beam is refocused by electromagnetic lens system so that beam is
directed with control( typically 0.25 mm diameter) towards work.
For controlling path of cut deflector coil is used to deflect electron beam.




 Kinetic energy of high velocity beam is transmitted into heat and
temperature of work increased above boiling point.

EBM process parameter:




Voltage: 1,50,000 V
Vacuum requirement: 133 x 10-6 N/m2
MRR: 1.6 mm3/min
Application:
To drill holes in pressure differential device and to
conductive and high melting point materials.
Advantage:
machine low thermal



Drill very small hole with high accuracy.
Brittle material can be easily machined.
Set up can be automated easily.
Disadvantage:



Vacuum chamber is essential
Equipment cost is high.
Low MRR and skilled operator required.

Electrochemical Machining (ECM)

Serv
(cathode)
n flow of
electrolyte
D C
Pump power
supply
0 +
for Tank
Electrolyte
ECM is metal
electroplating.
removal process based on principle of reverse
Filter Tool
used
Constant
tool feed
01-------,
Dov
t
.
Motor for
pun1p
Reservoir
Electrolyte

Non conventional machining process

Construction:
 It consist cathode(tool), Anode(work), Servomotor to control tool feed,
Electrolyte tank and it’s circulation arrangement, DC power
Servomotor controlled the feed of tool.
Pump is placed for providing strong stream of electrolyte.
supply.


Working:
 DC power supply provides current 50 to 40000 A at 5 to 30 V for across
the gap of 0.05 to 0.07 mm between tool and work. Electrolyte flows
through this gap at velocity 30 to 60 m/s.
 Current started flowing through electrolyte with positively charged
ions attracted towards the tool and negatively charged ions attracted
towards work.
 Due to this flow electrochemical reaction takes place and metal
removes in form sludge.
This sludge is taken away from gap by strong stream of electrolyte.

 Following reactions takes place while machining of pure iron
through ECM using NaCl+H2O as electrolyte.

ECM Process Parameter:





Voltage: 4 to 30 V
Current: 50 to 40000 A
MRR: 1600 mm3/min
Surface Finish: 0.1-2.5 m
Gap: 0.025 to 0.75 mm
(CLA)
Properties of Electrolyte:
Electrolyte provides several functions like complete the circuit, Remove
material from cutting region by pressure, Carry away heat to
generated.
High thermal and Electrical Conductivity
Low viscosity
Cheaper and Available
Non corrosive and Non toxic
Chemically Stable at process temperature.
be






Electrochemical Grinding (ECG)
or
Electrolytic Grinding
or
Anodic Machining

 It is combination of conventional mechanical grinding and electrochemical
machining in which material removed by electrolytic activity. In this
process mostly material removed by electrochemical decomposition and
remaining material is removed by abrasion of metal.
 ECG is widely used because it gives burrs free surface without producing
heat and after ECG, any secondary machining operation not required.

Construction:
 It consist of metallic grinding wheel as cathode, Work-piece as anode,
Electrolyte tank and circulation system.
Grinding wheel is maid such that diamond or aluminum oxide particles
embedded in it and it slightly projecting out from the surface so that they
touch work surface with a very little pressure. This abrasive particles
preventing direct contact between wheel and work piece.
As Electrolyte, non corrosive salt solution is used with water. It works as
both Electrolyte and coolant.


Working:
 DC power is supplied between electrodes and Grinding wheel start
rotating by means of motor.
Pump circulating electrolyte From reservoir tank to machining place.
When electrolyte entrapped in small cavities between work and abrasive
particles it forms electrolyte cell.
Current started flowing grinding wheel (Cathode) to work (Anode)
Oxide film forms on surface of work due to electro chemical oxidation and
this film is removed by projecting abrasive particles, which results in




Application:
 For grinding Carbide tools, refractory metals and Cobalt based alloy
ECG is used.
Advantage:



Process is independent of material hardness and strength.
Not completely depends on abrasive process.
Work is not subjected to any mechanical distortion and no heat
generation.
High surface finish and tool wear is negligible.
Rapid MRR.


Disadvantage:



Power consumption is more and High Capital cost.
Not applicable for non-conductive work-piece.
It is not suitable for soft materials.

 It is method of metal cutting with arc of plasma( jet of high velocity
ionized gas) that removes material from work-piece.
 At very higher temperature atoms of gas become ionized and this
stage of gas is known as Plasma.

Construction:


Plasma torch makes plasma and direct it for cutting.
Plasma torch consist gas chamber, Nozzle as Anode and Tungsten
electrode as Cathode and power supply.
Argon, nitrogen, hydrogen, or compressed air introduced around
cathode.

Working Principle:
 In gas chamber high velocity arc is generated between Anode and
Cathode. Gas molecules are collide with high velocity electrons of
arc and due to this gas gets ionized and large amount of heat
energy librated.
 This high velocity stream of hot ionized gas ( Plasma) is directed
on the work-piece to melt the material.

PAM Process Parameter:





Voltage: 30-250 V
Current: Up to 600 A
Power: 2-200 KW
Velocity of plasma jet: 500 m/s
MRR: 1,50,000 mm3/min
Advantages:



Any electrically conductive material machined regardless it’s hardness.
Doesn’t require any surface preparation.
It has high cutting rate.
Disadvantage:




Power consumption is very high.
High equipment cost.
It produced tapered surface.
Noise protection is required.

 In Chemical Machining process material is removed by chemical
dissolution using chemical reagents or etchants ( Acids or Alkaline
solutions).
Chemical reaction takes place between work surface and etchants
resulting into removal of material from surface.

 The surface which etched away, exposing
process is continued till the desired amount
Classification of Chemical Machining:
the lower layers and
of material removed.




Chemical
Chemical
Chemical
blanking
Milling
engraving

Steps for CM:
1) Residual stress
relieving
Cleaning the work
piece
Masking
Etching
De-masking
2)
3)
4)
5)

Application of CM:
 CM is used as chemical blanking for burr free etching of printed
chemical printed circuit boards, decorative panels.
 Chemical milling is commonly used in aerospace industry
shallow layers of material from large aircraft components
skin panels and airframe parts.
Advantage:
to remove
like missile
 It doesn’t distort the work and all the faces of work machined
simultaneously.
Low setup, maintenance and tooling cost.
It can be used to machine complex profiles
design parts.
Improves productivity.

 of delicate and intricate

Disadvantage:



Large tank and large floor area required.
High operation cost.
Chemicals used in process may be dangerous to health.

Ultrasonic Grinding
or
Ultrasonic Machining (USM)
or
Ultrasonic impact Grinding

It is mechanical material removal process in which material is
removed by repetitive impact of abrasive slurry on work surface, by
using high frequency oscillation of shaped tool.

Construction:
 It consist of Ultrasonic generator and transducer, Concentrator, tool,
Abrasive slurry and it’s feed mechanism, and tool feed mechanism.
Concentrator is tool cone which made from titanium or SS.
Tool is attached to base of concentrator by mean of silver brazing or
screws. Tool is shaped as approximate mirror image of cavity desired.
The gap between tool and work is about 0.02 to 0.1 mm.
Abrasive slurry is mixture of abrasive grains and carrier fluid which is
provided between tool and work-piece. Generally water is used as
carrier fluid.




Working:
 The ultrasonic transducer converts electrical energy into ultrasonic
waves or vibrations using magnetostrictive effects.
Tool vibrates longitudinally at 20 to 30 kHz with amplitude 0.02 mm
pressed on the work surface with light force.

 Concentrator increase the amplitude of vibration in order to give
required force amplitude ratio.

 The abrasive particle in form of abrasive slurry is continuous circulate
between tool and work. The tool performs hampering action on
abrasive particles.
The vibration of tool tip accelerates the abrasive particles at high rate
and it imparts the necessary force for cutting action.
 The tool is gradually moves down
maintain constant gap.
by means of tool feed mechanism to
USM Process Parameter:





Vibration frequency: 15 to 30 kHz
Vibration amplitude: 25 to 100 m
Gap: 0.02 to 0.1 mm
Surface finish: 0.2 to 0.8 m ( CLA)
MRR: 300 mm3/min

Application of USM:
 It is used for machining of hard and brittle material like ceramics, boron
carbide, titanium carbide.
 USM enables a dentist to drill a hole of any shape on teeth painlessly.
Advantage of USM:


Non-conductive materials can also machined.
There is no any change in microstructures, physical or chemical
properties.
Better surface finish and higher structure integrity.
Noiseless operation.


 Work piece harder than 60 HRC like carbide, Ceramics machined by USM.
Disadvantage of USM:




Low MRR.
High power consumption.
High tooling cost and it wears rapidly.
Not suitable for soft materials

Factors affecting MRR and surface finish in USM:






Tool amplitude and frequency.
Tool shape. Abrasive
grain size. Abrasive
concentration.
Work hardness-tool hardness ratio.
Feed force.

Abrasive jet machining
or
Micro-abrasive Blasting

Abrasive jet machining is mechanical energy based
unconventional machining process used to remove unwanted material
from a given workpiece.

Construction:
 It consist of Compressor ( To pressurize the gas ), Filter, mixing chamber,
Hopper, Vibrator, Nozzle, Pressure gauge and flow regulator.
The nozzle is made of a hard material like tungsten carbide.
 Abrasive used are aluminum oxide, Silicon carbide, or Sodium
bicarbonate.
The gases commonly used are air, N2, CO2.
Hopper is placed above mixing chamber for feeding purpose.
Vibrating device placed below mixing chamber to vibrate mixture of
abrasive and gas.



Working:


First dry air or gas is filtered and then it compressed by compressor.
A pressure gauge and flow regulator controls the pressure and regulate
the flow of the compressed air.
Compressed air entered into the mixing chamber where it mixed with
abrasive particles.


 Then mixture passes through nozzle where high velocity fine abrasive
jet is produced. The nozzle increases velocity about 200 to 400 m/s at
the expense of it’s pressure.
 As a result of repeated impact material removed from work due to
byerosion. Again new surface exposing
erosion.
AJM Process Parameter:
and so on material removed




Abrasive size: 25 m
Nozzle diameter: 0.13 to 1.2 mm
MRR: 0.8 mm3/min
Application:



Drilling, Cleaning, and polishing of hard surface.
To machine intricate shapes which is difficult to machine.
Aircraft fuel system, Medical appliances and Hydraulic valves.

Advantage of Abrasive Jet Machining:





No heat is generated in work. So it is suitable for
No physical contact between tool and work.
Thin and fragile materials also machined.
Low investment.
Smooth surface finish.
heat sensitive materials.
Disadvantage:



Low MRR.
Abrasive powder cannot be reused.
Nozzle life is less and maintenance of nozzle required.
Factors affecting performance of AJM:





Abrasive grain size and It’s mass flow rate
Mixing ratio.
Velocity of abrasive particles.
Gas pressure.
Nozzle tip distance.

Comparison between various
Non-conventional Machining Process

Surface
finish
m ( CLA)
Power
consumption
Tooling
Cost
Investment
cost
MRRProcess Medium Efficiency
Liquid
dielectric
EDM 0.2-1.2 800 Low High Medium High
ECM Electrolyte 0.1-2.5 1500 Medium Medium Very high Low
High
(Chemical
cost)
Liquid
chemical
CM 0.5-2.5 15 low Medium Medium
LBM Air 0.5-1.2 0.1 Very low Low Low Very high
EBM Vacuum 0.5-2.5 1.6 Low Low High Very high
PAM Argon Rough 75000 Very low Low Very low Very low
Abrasive in
water
USM 0.2-0.5 300 Low Low Low High
Abrasive in
AJM 0.5-1.2 0.8 low low Very low High

Non conventional machining process

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