UCM - Unit 5 recent trends in non-traditional machining processes

UNIT -V
RECENT TRENDS IN NON-
TRADITIONAL MACHINING
PROCESSES

INTRODUCTION
• Recent developments in non traditional
machining process is the hybrid process. This
process was developed by combining the
advantages of two non traditional machining
processes and eliminating the limitations of
those processes.

VARIOUS TYPES OF HYBRID PROCESS
1. Electric discharge diamond grinding (EDDG)
2. Electro chemical spark machining (ECSM)
3. Magneto rheological abrasive flow finishing
(MRAFF)

• It enhances volumetric material removal rate.
• Computer controls of the processes have
good results and better performance.
• Awareness of capabilities will resolve many
problems in machining.
• Application of adaptive control machining
becomes easier.
MAIN PURPOSES OF
IMPLEMENTING HYBRID PROCESS

Electro chemical spark machining
(ECSM)
• Electro chemical spark machining is a hybrid
process of electro chemical machining and
electric discharge machining. This process is
Unique because it is suitable for both
conducting and non conducting material.
• It is used for selective deposition,
microwelding and machining of special non
conductive material

• The anode and the cathode are immersed
inside the electrolyte. Due to potential
difference developed, hydrogen bubbles are
generated and thus spark is created between
the cathode and workpiece.
• This produces high energy that helps in
material removal or vapourization of material
take place as shown in figure
PRINCIPLE OF (ECSM)

Electro chemical spark machining
(ECSM)

ELECTRO CHEMICAL SPARK
MACHINING (ECSM)

MATERIAL REMOVAL IN ECSM
• Melting and vapourisation
• Chemical reaction when proper electrolyte is
not selected.
• Cracks propagate through random thermal
stresses.
• Due to mechanical shock and cavitations
effect.

PROCESS PARAMETERS IN ECSM
• A supply voltage ranges between 35 – 50 V.
• Cutting tool has a wire diameter of 200 m.
• The workpiece used here is soda lime glass.
• The gap to be maintained between the cathode
and workpiece is around 50 – 500 m depending
on the type of application.
• The electrolyte solution is 14 – 20% of water and
sodium chloride.
• The table speed is 4 rpm.

• Electric discharge diamond grinding process is
a spark erosion process used for precision
grinding. Spark is produced between metal
bonded grinding wheel and workpiece.
• Heat generated during sparking softens the
workpieces surface and grinding process is
easily abraded using diamond abrasive
particles.
ELECTRICAL DISCHARGE DIAMOND
GRINDING (EDDG)

ELECTRICAL DISCHARGE DIAMOND
GRINDING

Formation of Spark in an Abrasive

• When the workpieces is the electrically
conductive material
• When the workpiece is electrically
nonconductive material.
BASIC CONFIGURATION OF EDDG

• Wheel speed
• Current
• Pulse on time
• Diamond particle size
• Bond material
• Dielectric material
• Voltage
MAIN PARAMETERS USED IN EDDG

FACTORS AFFECTING PROCESS
PARAMETERS OF EDDG
1. Wheel speed
2. Current
3. Pulse on time

• It can grind any conductive and non conductive
materials.
• Less corrosive effect is produced.
• This process involves continuous dressing and
declogging of the abrasive wheel and thus
increases the wheel life to 25%.
• Higher material removal rate than EDM
• Lower operating cost
• Produces higher accuracy
ADVANTAGES OF EDDG

• Recast layer is formed after grinding
• Possibilities of oil fires
• Wheels are fragile
DISADVANTAGES OF EDDG

APPLICATION OF EDDG
• It is used in grinding of thin sections
• Grinding of high hardness materials such as
cermates, super alloys and metal matrix
composites.

MICROMACHINING
• Micromachining is machining of miniature
components. It is also defined as removal of
material in the form of chips or debris having
the size in the range of micron with
dimensions greater than or equal to one micro
and smaller than or equal to 999 micron.

• Minimising energy and material use
• Faster devices
• Increased selectively and sensitivity
• It has improved accuracy and reliability
• It is basically concern with machining of micro
/ nano components or material or material
removal at micro / nano level.
FEATURES OF MICROMACHINING

Classification of Advanced Micro
Machining Processes

• The working principle of advanced mechanical
type micro machining processes are fine
abrasive particles with high kinetic energy bits
the workpiece at an angle.
ADVANCED MECHANICAL MICRO
MACHINING PROCESSES

• Abrasive jet micromachining
• Abrasive waterjet micromachining
• Ultrasonic micromachining
ADVANCED MECHANICAL MICRO
MACHINING PROCESSES

• Abrasive jet micromachining works in the
same principle of abrasive jet machining (AJM)
• A high speed stream of mixture of fluid (air or
gas) with abrasive particle is injected through
the nozzle on the workpiece to be machined.
ABRASIVE JET MICROMACHINING

• Particle size
• Size distribution
• Moisture content and
• Surface texture
Powder flowability and
compactability depends on

Steps involved in abrasive jet micro
machining

Pressurized powder feed system

EFFECT OF PROCESS PARAMETER IN
AJMM
• Powder compaction
• Powder stratification
• Powder humidity

ADVANTAGES AND DISADVANTAGES
OF AJMM
ADVANTAGES
• Shallow holes can be accurately machined.
• Machining of grooves with the use of mask
pattern or target material can be done.
DISADVANTAGES OF AJMM
• Low erosion rate
• Minimum thickness of the substrate should be
0.3 mm or otherwise buckling of the plate occurs.
• Constant powder feeding is affected due to
compaction, stratification and humidity.

APPLICATIONS OF AJMM
• Micro accelerometer beam
• Matrix of micro E-cores
• Capillary electro phores is chips
• 3D suspended microstructures
• 3D passive glass micro mixer.

ABRASIVE WATERJET
MICROMACHINING
• Abrasive waterjet micromachining works in
the same principle of abrasive waterjet
machining.
• Abrasive waterjet cut by erosion. A million of
such particles impact on a workpiece per
second travelling with 2 times the speed of
sound for machining the work surface.

• Abrasive water jet generation
• Abrasive waterjet subsystem
• Abrasive waterjet machining centers.
COMPONENTS OF AWJMM

Cutting head of abrasive waterjet

ABRASIVE WATERJET
• ultra high pressure water at 3000 to 6000 bar
• water speed is 750 m/s

ABRASIVE WATER JET SUBSYSTEM
• Ultra high pressure water feed system
• The cutting head
• Abrasive feed system

Abrasive Water Jet Micro Machining
Centre
• Motion system - ball screw and linear motors.
• Machine structure
• Workpiece holding
• Human machine interface and control system

ADVANTAGES OF AWJMM
• Alloy steel and all grades of stainless steel can be machined.
• Machining of layered materials such as rubber or polymer
bonded to metal can be cut.
• It can cur thicker material than a laser.
DISADVANTAGES OF AWJMM
• Difficult to machine metals like armour plating, titanium and
copper base alloys.
• High residual stresses are produced in thin and toughened
glass during machining.
OF AWJMM

• Used in jewellery and craft markets
• Used in precision cleaning, peening to remove
and dismantle nuclear plants
• Used in cutting precision pocket milling,
turning and drilling.
APPLICATIONS OF AWJMM

• Ultrasonic micromachining process works in
the same principle of ultrasonic machining
process.
• Ultrasonic micromachining produces
ultrasonic vibration, when combined with a
abrasive slurry to create a accurate cavity of
any shape through the impact of fine grains.
Ultrasonic micromachining is a mechanical
process that it produces high quality surface.
ULTRASONIC MICROMACHINING
PROCESS

Schematic arrangement of ultrasonic
micromachining

Material removal in ultrasonic micro
machining

• High frequency oscillating current generator
• The acoustic head
• Tool spindle mechanism
• Controlled axes
• The micro tool
• Abrasive slurry
• Workpiece
ULTRASONIC MICROMACHINING HAS
7 BASIC COMPONENTS

• The range of output produced is 5 to 15 kW
and controlled range of 19-22 kHz. The main
function of this generator is to convert low
frequency 50 Hz electrical power to high
frequency 220 Hz.
• It has 2 parts (i) Transducer (ii) horn.

• High wear resistance
• Good elasticity and fatigue strength
• Optimum toughness and hardness
• Cemented carbide tools are used for its
hardness toughness and thermal conductivity
that is used to cut glass.
Microtool

• The slurry consists of small abrasives particles
mixed with water or oil and abrasive
concentration 30 to 60% by weight
• Alumina is best for cutting glass, germanium and
ceramics
• Diamond powder for cutting diamond rubies
• The size of the abrasives range between 300 to
2000 grit
• Coarse grades are used for roughing operation
Abrasive Tools

FACTORS AFFECTING PROCESS
PARAMETER
• machining rate
• surface finish
• machining accuracy
• toolwear

1.Amplitude of vibration = 5 μm
2. Workpiece material = silicon
3. Tool material = Tungsten
4. Tool size = 50, 100,150 μm
5. Abrasive grain type = polycrystalline diamond
powder
6. size = 1 – 3 μm
7. Total tool feed = 515 μm
PROCESS VARIABLES OF USMM

• Effect of process parameters on material
removal rate
• Effect of process parameter on tool wear
• Effect of process parameter on surface finish
• Effect of process parameter on accuracy
EFFECT OF PROCESS PARAMETERS ON
QUALITY CHARACTERISTICS OF USMM

Material removal rate (MRR) depends upon
• Machining parameters
• Abrasive slurry
• Work material properties
• Tool material properties and tool geometry
The machining parameters that affect the material
removal rate are
• amplitude of vibration
• frequency of vibration
• static load
MATERIAL REMOVAL RATE

The factors that influences tool wear are
• Static load
• Work material
• Tool size
• Tool material
• Type of abrasives and its grain size
• Machining time
• Depth of machining
TOOL WEAR

Effect of Machining Parameter on
Surface Finish
• By using fine grains
• Driven by smaller vibrations and amplitude.
• Smaller static force at smaller depth of cut and
larger lateral feed.
• Larger grain size of 2 to 120 m is used for
roughing operation.
• Smaller grain size of 0.2 to 10 m is used for
finishing operations

The factors affecting accuracy in USMM are
• accuracy of feed motion
• accuracy of fixtures used
• quality of assembly element
• abrasive grit size
• tool wear
• transverse vibration effect
• depth of cut
Effect of Process Parameter on
Accuracy

• Machining of any materials regardless of their conductivity
• Machining of semiconductor as silicon germanium
• Suitable for machining precise brittle materials
• Can drill circular or non circular holes in hard materials
• Less stress is produced because of its non thermal
characteristics
DISADVANTAGES
• Low material removal rate
• Tool wear is faster in USMM
• Machining area and depth is restrained in USMM.
OF USMM

APPLICATIONS OF USMM
• Used for making press tool dies
• Drilling small holes in helicopter power transmission
shaft
• Drilling of diamond dies, machining of aluminium
oxides Al2O3
• Producing hollow cubes
• Used in surgical tools manufacturer for better
evaculation of chips
• Plague from the teeth are removed without any
damage

THERMAL ADVANCED
MICROMACHINING PROCESSESS
• In thermal advanced micromachining intense heat is
produced and localized which increases the workpiece
temperature in a zone or beam diameter equal to its
melting and vapourization temperature.
• The material removal is at micro-nano level in form of
debris.
Types of thermal advanced micromachining
(i) Electric discharge micromachining
(ii) Electron beam micromachining
(iii) Laser beam micromachining

Electric Discharge Micro Machining
• Electric discharge micromachining (EDMM)
works in the same principle of electric
discharge machining (EDM).
• EDM removes material by thermal erosive
action of electrical discharge (spark) produced
by a pulse DC power supply between anode
and cathode. The tool acts as the cathode and
the workpiece acts as the cathode and the
workpiece acts as the anode.

TYPES OF ELECTRODES AND THEIR
MATERIALS

Types of dielectric fluids and its
properties

Schematic arrangement of electric
discharge micromachining

Single Spark erosion in electric
discharge micro machining

Three stages involved in formation of
spark

• Prebreakdown phase – The initial stage of the
ignition stage is prebreakdown phase.
• During this phase two phenomena occurs that
breakdown of dielectric between electrodes take
place.
(i) Bubble formation
(ii) Electronic impact mechanism
• The temperature of the embroyonic plasma
increases and the energy balance equation is
given by
IGNITION STAGE

• The power utilization is given by
• Work done during expansion of plasma channel
• Power flux utilized for vaporization and
dissociation of dielectric media.
• Power flux dissipating towards anode and
cathode.
• The power fraction utilized by the plasma
Pcircuit = V(t) X I(t)
HEATING STAGE

• In the removal stage, the heat generated during
plasma formation and expansion is transferred to
anode and cathode by two ways.
I)By radiation heat transfer
II) Ion or electron bombardment
• The power transfer due to particle bombardment
and radiation flux is given by
△Pcathode = △Pions + △Pelectron + △Pradiation
Removal Stage

• Mechanism of material removal by melting
and evaporisation.
• Material removal rate is between 0.6 to 6
mm3 /hr
• Dimensional accuracy is 2 m (sinking EDM)
and 1 m (wire EDM).
• Surface finish is 0.4 to 0.5 m
PROCESS PARAMETERS OF EDMM

• Dielectric - Water is used as dielectric which
provides good discharge repetition rate.
• Tool - Electrode wear can be reduced by using
diamond electrode.
• Workpiece
EDMM

ADVANTAGE
• It is used for cutting complex or odd shape
materials that are electrically conductive.
• It is used in machining hardened materials
• It has high machining rate
• It has good dimensional accuracy and surface
integrity.
DISADVANTAGE
• It is not suitable for high aspect ratio holes and
features.
OF EDMM

• Used in drilling 6.5 holes in 50 m plate
• Used in making 1.2 slots in 2.5 m wall.
• Used in shaping microfluids mixer and channel
• Used in machining microgears or internal
gears.
APPLICATIONS OF EDMM

• EBMM works on the same principle of EBM.
Electron beam micromachining uses a high
velocity stream, of electron focused on the
workpiece surface to remove material by
melting and vapourization.
ELECTRON BEAM MICROMACHINING
PROCESS

• The main components of EBMM are the electron
gun, the anode, cathode, magnetic lens and
deflection coils with a vacuum chamber.
• The anode applies a potential field that
accelerates the electron with voltage of approx
50000 to 200000volts to create velocity over
200000 km/s.
• The power is defined by the accelerating voltage
and the beam current which ranges from 100 μA
to 1 Amps.
CONSTRUCTION AND WORKING

• An electromagnetic lens reduce the area of
the beam to a diameter of 25 μm.
• This beam of fast moving electron gets
focused to 10 to 200 μm area at density of
6500 GW/mm2
• The pulse duration ranges from 50 μs to 10 ms
• This process is limited to thin parts in the
range of 0.2 to 6 mm thick.
CONSTRUCTION AND WORKING

Mechanism of material removal in drilling
of electron beam micro machining

• The pulse time and beam current level of the pulse
ensure high reproductability.
• Beam current varies from 100 μA to 1 A and governs
the energy / pulse being supplied to workpiece.
• Pulse duration for EBMM ranges from 50 μs to 10 ms.
• The working distance and the focused beam diameter
are determined by magnitude of current.
• The permissible minimum distance between 2 drilled
holes is in order of 2 to 3 times the hole diameter.
PROCESS PARAMETERS OF EBMM

• Pulse beam time and operation
• Cutting speed
• Source disposal effect and power retention
factor
• Conduction losses and temperature rises
• Heat affected zone
• Cross sectional area of beam
EFFECT OF PROCESS PARAMETER ON
EBMM

ADVANTAGES
• It is easy to modulate the electron beam
parameters
• High precision stresses on the workpieces are
relaxed due to rise in temperature of the material
DISADVANTAGES OF EBMM
• The process is conducted in vacuum
• Requirement of high energy
• The equipment is expensive
OF EBMM

• Used for drilling and cutting of metals, non metals,
ceramics and composite
• Used to drill thousands of hole on the material both
electrically conductive and non conductive material
• Used in making fine gas orifices in space nuclear reactors.
• Used in drilling holes in wire drawing dies
• Used in metering holes in injector nozzle of diesel engine.
• Employed for pattern generations for integrated circuit
fabrication
• Used in drilling small diameter holes 250 μm
• Used in drill holes with very high depth to diameter ratio.
APPLICATIONS OF EBMM

• Laser consists of an amplifying medium where
stimulated emission and amplification of light is
created.
• Mirrors are used as optical resonators and oscillation
occurs because of amplifying medium. An optical
resonator provides a feedback and a pump source to
input energy in the amplifying medium. Laser is placed
between suitable aligned mirrors.
• The types of lasers used for machining are CO2 laser,
excimer laser yattrium, Aluminium, sapphire laser.
LASEB BEAM MICRO MACHINING
PROCESS

1. Direct writing
2. Mask projection
3. Interference technique
• specific power consumption - 1000 W/mm3/min
• MRR - 5 mm3/min
MECHANISM OF MATERIAL REMOVAL
IN LBMM

Laser direct writing technique

Mask Projection Technique and
Laser Interference Technique

Laser and Material Interaction
Process

• Mechanism of material removal by melting and
vapourization
• Medium – normal atmosphere
• Tool – High power laser beam
• Maximum MRR – 5 mm3 /min
• Specific power consumption = 100 W/mm3 min
• Material – All material except material of high reflectivity
(Aluminum and copper)
• Shape applications – drilling five holes
• Limitation – very high power consumption cannot machine
materials with high heat conductivity and reflectivity
PROCESS PARAMETERS OF LBMM

ADVANTAGES OF LBMM
• This process is forceless and contactless
• Minor heat affected zone
• machining is free from burr and bulging
• No additional tooling cost by wear
• Material removal rate is controllable.
DISADVANTAGES OF LBMM
• Very high power consumption
• It cannot machine materials of high
• High conductivity and reflectivity
• Not suitable for Aluminium and copper
• The equipment required for micromachining is very costly
• Need highly skilled operators to machine
OF LBMM

• It is used in machining threads in a single poly fibre.
• Machining of microholes and microchannels on
integrated chips.
• Micro cutting in tungsten pin using 511 nanometer
using ND laser
• Micro fluidic devices in silicon showing laser drilled
holes and connecting channels
• Micro machined letters on a single human hair
• Cutting of 1mm tube cutting, 100 μm wide V grooves
APPLICATIONS OF LBMM

• Electro chemical micromachining works in the
same principle of Electro chemical machining.
• Faraday’s law of electrolysis states that the
amount of substance deposited or dissolved in
proportional to the quantity of electricity that
is passed through the electrolyte.
ELECTRO CHEMICAL
MICROMACHINING PROCESS

Electrolyte of ECMM
• Electrolyte are basically two types.
• Passive electrolyte containing oxidizing anions
(sodium nitrate, sodium chloride)
• Non passive electrolyte containing aggressive
anions (sodium chloride)

IEG – Inter Electrode Gap
• In ECMM process, the IEG is kept in range of 6 -15μm.
• Methods of monitoring and measuring the IEG is during
pulse of time of 0.1 to 5ms.
• Machining accuracy is directly proportional to the inter
electrode gap size.
Micro Tool Design and Fabrication
• The computer based tool design for ECMM is feasible,
economical and time saving one.
• Micro tools are fabricated using electro chemical etching
and wire electro discharge grinding as shown in figure
Inter Electrode Gap

Anodic Reaction and Current
Efficiency

Through Mask ECMM – 3scales are considered
• Workpiece scale – geometry of the workpiece
can be controlled by the current distributions
• Pattern scale – Current distribution depends
upon the spacing of the features and their
geometry
• Feature scale – shape is evaluated through the
current distribution.
Current Distribution and Shape
Evolution

• Nature of power supply
• Inter electrode gap
• Concentration, temperature and electrolyte
flow.
• Microtool feed rate
ECMM

ADVANTAGES
• Precision manufacturing of miniature
components
• Production of high accuracy holes.
DISADVANTAGES
• Material removal rate is very low
• The equipment used is of high cost
OF ECMM

• 3D micromachining of microstructure in copper
sheet used in electronic circuit board
• Smooth surface and sharp borders are machined
in titanium surfaces by using mask ECMM
• Manufacture of nozzle plate for inkjet printer
heads.
• Use in aerospace, automobile and other heavy
industries for shaping, sizing, deburring and
finishing operation.
APPLICATIONS OF ECMM

UCM - Unit 5 recent trends in non-traditional machining processes

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UCM - Unit 5 recent trends in non-traditional machining processes