Non convention machining process,Advanced Machining Process,Production Technology

PROF. MAYUR S MODI
Assistant Professor
Mechanical Engineering Department
SSASIT, Surat
Non-conventionalNon-conventional
Machining ProcessMachining Process
Production technology
(181903)
PROF.M.S.MODI

Introduction
• In recent years a number of new material have
been developed which are being commonly used
in space research missiles and nuclear industry.
• These materials are stronger, harder, tougher,
heat and wear resistant and cannot be machined
by this conventional machining process.
• These difficulties of conventional machining
process are solved by this process.
• It is new metal removing process called newer
machining process or unconventional machining
process.
PROF.M.S.MODI

Classification
• Mechanical metal removing process.
• 1. Ultrasonic machining (USM)
• 2. Abrasive jet machining (AJM)
• 3. Water jet machining (WJM)
• Electrochemical method.
• 1. Electrochemical machining (ECM)
• 2. Electrochemical grinding (ECG)
• Thermal metal removing process
• 1. Electro discharge machining (EDM)
• 2. Plasma arc machining (PAM)
• 3. Electron beam machining (EBM)
• 4. Laser beam machining (LBM)
PROF.M.S.MODI

A machining process is called non-traditional if
its material removal mechanism is basically
different than those in the traditional processes,
i.e. a different form of energy (other than the
excessive forces exercised by a tool, which is in
physical contact with the work piece) is applied
to remove the excess material from the work
surface, or to separate the work piece into
smaller parts.
PROF.M.S.MODI

Non-traditional processes generally should be
employed when
1.There is a need to process some newly developed
difficult to- cut materials, machining of which is
accompanied by excessive cutting forces and tool wear;
2.There is a need for unusual and complex shapes, which
cannot easily be machined or cannot at all be machined
by traditional processes;
PROF.M.S.MODI

Ultrasonic Machining
• Process principle, process parameters and their
Applications
• Utilizes mechanical energy for material removal by
erosion - for conducting and non-conducting materials.
PROF.M.S.MODI

•The acoustic head is the most
complicated part of the machine. It
must provide a static constant
force, as well as the high frequency
vibration.
•Tools are produced of tough but
ductile metals such as soft steel of
stainless steel.
•Aluminum and brass tools wear
near 5 to 10 times faster.
•Abrasive slurry consists of a mixture of liquid (water is the most
common but oils or glycerol are also used) and 20% to 60% of
abrasives with typical grit sizes of 100 to 800. The common types
of abrasive materials are boron carbide, silicon carbide, diamond,
and corundum (Al2O3).
PROF.M.S.MODI

Applications
• The ultrasonic machining process can be used to
cut through and blind holes of round or irregular
cross-sections.
• The process is best suited to poorly conducting,
hard and brittle materials like glass, ceramics,
carbides, and semiconductors.
PROF.M.S.MODI

Typical examples produced
by USM
PROF.M.S.MODI

Process Parameters
The critical parameters to control the process are
• Tool frequency,
• Amplitude and material,
• Abrasive grit size(200-400 for rough and 800-
1000 for finished) and material,
• Feed force,(Tool amplitude 0.01 -0.06 mm)
• Slurry concentration(20-60 % by volume of the
abrasives)
• Viscosity.
PROF.M.S.MODI

BE SEM-VIII Examination
May 2012
• Describe Ultrasonic Machining (USM) process with neat
sketch. Discuss how the following factors effects the material
removal rate of USM. (7 Marks)
• (i) Grain Size (iv) Feed force
• (ii) Frequency (v) Hardness ratio
• (iii) Amplitude (vi) Abrasive concentration
PROF.M.S.MODI

Abrasive Jet Cutting
Machines
PROF.M.S.MODI

Introduction
• Abrasive jet cutting machines which are used to
cut sheet materials or to remove materials of
work piece from a surface by generating a
focused stream of fluid mixed with abrasive
particles.
• Abrasive jet cutting machines includes four main
types of devices abrasive water jet cutters, air
abrasive jet cutters, and precision blaster or
micro-jets.
• They are used for drilling, detailing and precision
cutting of printed circuit boards and other high
quality components.
PROF.M.S.MODI

Principal Process
PROF.M.S.MODI

• The high pressure air/gas entrains the abrasive particles
and this mixture emerges from a small nozzle at high
velocity.
• This stream of abrasive particles strikes the work piece at
nearly the speed of sound and cuts the material
PROF.M.S.MODI

The process parameters are listed
below:
• Abrasive
1.Material – Al2O3/ SiC / glass beads
2.Shape – irregular / spherical
3.Size – 10 ~ 50 μm
4.Mass flow rate – 2 ~ 20 gm/min
• Carrier gas
1.Composition – Air, CO2, N2
2.Density – Air ~ 1.3 kg/m3
3.Velocity – 500 ~ 700 m/s
4.Pressure – 2 ~ 10 bar
5.Flow rate – 5 ~ 30 lpm
PROF.M.S.MODI

• Abrasive Jet
1.Velocity – 100 ~ 300 m/s
2.Mixing ratio – mass flow ratio of abrasive to gas =
3.Stand-off distance – 0.5 ~ 5 mm
4.Impingement Angle – 60 ~ 90
• Nozzle
1.Material –sapphire
2.Diameter – (Internal) 0.2 ~ 0.8 mm
3.Life – 10 ~ 300 hours
PROF.M.S.MODI

Advantages
• Ability to cut brittle or heat sensitive material without
damage.
• Ability to cut intricate holes in material of any hardness.
• Low capital cost.
• Surface finish obtain is good.
• Virtually no heat is generated in the work piece
PROF.M.S.MODI

Disadvantages
• Slow material removal rate.
• Stray cutting and hence accuracy is not good.
• Abrasive powder cannot be reused.
• Embedding of abrasive in the work piece.
• A suitable dust collecting system is required.
PROF.M.S.MODI

Applications
• Cleaning purpose.
• Cutting fine lines.
• Machining semiconductors.
• Drilling and cutting thin section of hardened metal.
• Removing plating, anodic or, thermal oxide coating
• Cutting and etching, quartz, mica etc.
PROF.M.S.MODI

PROF.M.S.MODI
ELECTRICAL DISCHARGE
MACHINING

Objectives
• Describe the basic working principle of EDM process
• Draw schematically the basics of EDM
• Describe spark initiation in EDM
• Describe material removal mechanism in EDM
• Identify the process parameters in EDM
• Describe the characteristics of EDM
• Identify the purpose of dielectric fluid in EDM
• Analyse the required properties of EDM tool
• List four common tool material for EDM
• Develop models for material removal rate in EDM
PROF.M.S.MODI

Introduction
• Electro Discharge Machining (EDM) is an
electro-thermal non-traditional machining
process, where electrical energy is used to
generate electrical spark and material removal
mainly occurs due to thermal energy of the spark.
• EDM is mainly used to machine difficult-to-
machine materials and high strength temperature
resistant alloys.
• EDM can be used to machine difficult geometries
in small batches or even on job-shop basis. Work
material to be machined by EDM has to be
electrically conductive.
PROF.M.S.MODI

• Based on erosion of metals by spark discharges.
• EDM system consist of a tool (electrode) and
work piece, connected to a DC power supply and
placed in a dielectric fluid.
• when potential difference between tool and work
piece is high, a transient spark discharges through
the fluid, removing a small amount of metal from
the work piece surface.
• This process is repeated with capacitor discharge
rates of 50-500 kHz.
PROF.M.S.MODI

• Dielectric fluid mineral oils, kerosene, distilled and de
ionized water etc.
• Role of the dielectric fluid
1. Acts as a insulator until the potential is sufficiently high.
2. Acts as a flushing medium and carries away the debris.
3. Also acts as a cooling medium.
• Electrodes usually made of graphite.
• EDM can be used for die cavities, small diameter deep
holes, turbine blades and various intricate shapes.
PROF.M.S.MODI

• Cold emmision
• Collision take place, mainly depends on energy of
electron and die electric fluid molecules.
• Cyclic process.
• Plasma (channel) state generated.
• Finally electrical energy is converted into thermal energy.
• 10,000 degree C temp. can achived.
• Plasma state is not for longer period of time so it will
collapsed and it generates pressure and shock waves,
which evacuates the molten metal forming and crater of
removed material around the site of the spark.
PROF.M.S.MODI
SPARK IGNITION

• Thus to summarise, the material removal in
EDM mainly occurs due to formation of shock
waves as the plasma channel collapse owing to
discontinuation of applied potential difference.
PROF.M.S.MODI

• The waveform is characterized by the
PROF.M.S.MODI

Characteristics of EDM
(a) The process can be used to machine any work material
if it is electrically conductive
(b) Material removal depends on mainly thermal properties
of the work material rather than its strength, hardness etc
(c) In EDM there is a physical tool and geometry of the
tool is the positive impression of the hole or geometric
feature machined
(d) The tool has to be electrically conductive as well. The
tool wear once again depends on the thermal properties of
the tool material
PROF.M.S.MODI

(e) Though the local temperature rise is rather high, still
due to very small pulse on time, there is not enough time
for the heat to diffuse and thus almost no increase in bulk
temperature takes place. Thus the heat affected zone is
limited to 2 – 4 μm of the spark crater
(f) However rapid heating and cooling and local high
temperature leads to surface hardening which may be
desirable in some applications
(g) Though there is a possibility of taper cut and overcut in
EDM, they can be controlled and compensated.
PROF.M.S.MODI

Dielectric
• In EDM, as has been discussed earlier, material removal
mainly occurs due to thermal evaporation and melting.
• As thermal processing is required to be carried out in
absence of oxygen so that the process can be controlled
and oxidation avoided.
• Oxidation often leads to poor surface conductivity
(electrical) of the work piece hindering further
machining. Hence, dielectric fluid should provide an
oxygen free machining environment.
PROF.M.S.MODI

• Further it should have enough strong dielectric resistance
so that it does not breakdown electrically too easily but at
the same time ionise when electrons collide with its
molecule. Moreover, during sparking it should be
thermally resistant as well.
• Generally kerosene and deionised water is used as
dielectric fluid in EDM. Tap water cannot be used as it
ionises too early and thus breakdown due to presence of
salts as impurities occur.
• Dielectric medium is generally flushed around the spark
zone. It is also applied through the tool to achieve
efficient removal of molten material.
PROF.M.S.MODI

Electrode Material
• High electrical conductivity – electrons are cold emitted
more easily and there is less bulk electrical heating
• High thermal conductivity – for the same heat load, the local
temperature rise would be less due to faster heat conducted
to the bulk of the tool and thus less tool wear
• Higher density – for the same heat load and same tool wear
by weight there would be less volume removal or tool wear
and thus less dimensional loss or inaccuracy
• High melting point – high melting point leads to less tool
wear due to less tool material melting for the same heat load
• Easy manufacturability
• Cost – cheap
• Graphite , Electrolytic oxygen free copper ETC...
PROF.M.S.MODI

Wire EDM
• This process is similar to contour cutting with a band
saw.
• A slow moving wire travels along a prescribed path,
cutting the work piece with discharge sparks.
• Wire should have sufficient tensile strength and fracture
toughness.
• Wire is made of brass, copper or tungsten. (About
0.25mm in diameter).
PROF.M.S.MODI

Advantages
• Material of any hardness can be machined
• No burrs are left in machined surface
• One of the main advantaged of this process is that thin
and fragile/brittle components can be machined without
distortion.
• Complex internal shapes can be machine
PROF.M.S.MODI

Limitations
• Cant be applied to electrically non
• non-conducting materials. The surface machined , in
some of the cases, has been found to have micro cracks.
• Tool wear can limit the degree of accuracy attainable.
• Normally applicable to small sized jobs.
PROF.M.S.MODI

Applications
• Spark machining
• Spark erosion
• Extensively applied for the machining of exotic materials.
PROF.M.S.MODI

ChemicalMachining (CM)
PROF.M.S.MODI

PROF.M.S.MODI
CHEMICAL MILLING

• Residual stress relieving
If the part to be machined has residual stresses from the
previous processing, these stresses first should be relived
in order to prevent warping after chemical milling.
• Preparing surfaces
The surfaces are degreased and cleaned thoroughly to
ensure both good adhesion of the masking material and
the uniform material removal
• Scribing
A template is placed over the part and the areas to be
exposed to the etchant are circumscribed and the masking
material stripped away.
PROF.M.S.MODI

• Masking
masking material is applied.(coating or protecting areas
not to be etched)
• Etching
The exposed surfaces are machined chemically with
etchants
• Demasking
After machining, the parts should be washed thoroughly
to prevent further reactions with or exposure to any
etchant residues. Then the rest of the masking material is
removed and the part is cleaned and inspected.
PROF.M.S.MODI

PROF.M.S.MODI
CHEMICAL MACHINING

PROF.M.S.MODI
CHEMICAL BLANKING

Introduction
• ECM is based on the electrolysis
• Electrochemical machining (ECM) is a method of
removing metal by an electrochemical process.
• It is normally used for mass production and is used for
working extremely hard materials or materials that are
difficult to machine using conventional methods.
PROF.M.S.MODI

• Its use is limited to electrically conductive materials.
• ECM can cut small or odd shaped angles, intricate
contours or cavities in hard and exotic metals, such as
nickel alloy, cobalt alloy, aluminum alloys. Both external
and internal geometries can be machined.
• In the ECM process, a cathode (tool) is advanced into an
anode (work piece).
• The pressurized electrolyte is injected at a set
temperature to the area being cut.
PROF.M.S.MODI

PROF.M.S.MODI
Electrochemical machining is a process of a selective
dissolution of the anodically connected work piece
material submerged in an electrolyte together with an
anodically connected tool.

Advantages of electrochemical machining:
• The rate of machining does not depend on the
hardness of the work piece material.
• The tool does not wear. Soft materials (e.g.,
copper) may be used for tool fabrication.
• No stresses are produced on the work piece
surface.
• No burrs form in the machining operation.
• High surface quality may be achieved.
• High accuracy of the machining operation
PROF.M.S.MODI

Disadvantages of electrochemical machining:
• Higher cost.
• Electrolyte may cause corrosion of the equipment.
• Large production floor is required.
• Only electrically conductive materials may be
machined.
• Not environmentally friendly process.
PROF.M.S.MODI

Application
• 1. Small deep hole.
• 2. To machine through holes of any cross-
section.
• 3. To machine blind holes and shaped cavities
such as in forging dies.
• 4. To machining jet engine blade cooling holes.
PROF.M.S.MODI

Introduction
Electrochemical grinding (ECG) is an electrolytic
material-removal process involving a negatively charged
abrasive grinding wheel, a conductive fluid (electrolyte),
and a positively charged work piece. Work piece material
depletes in to the electrolyte solution. ECG is similar to
electrochemical machining except that the cathode is a
specially constructed grinding wheel instead of a tool
shaped like the contour to be machined.

Defination
ECG is the material removal process in which the material
is removed by the combination of Electro- Chemical
decomposition as in ECM process and abrasive due to
grinding.

Process Characteristics
Utilizes electrically conductive grinding wheels
Removes material by electrochemical
decomposition and abrasive action
Deplates work piece materials and deposits them
in electrolyte
Wheels wear extremely slowly
Work pieces are electrically conductive

Materials Can Be Machined
Aluminum
Amorphous metals
Berilium
Berilium Copper
Copper
Hastelloy™
Inconel
Iridium
Neodymium Iron Boron
Nickel Aluminide
Nitinol
PH 17-4 Stainless Steel
Powdered Metals
Rene 41
Rhenium
Rhodium
Stainless Steel
Stellite
Titanium
Tungsten Carbide
Vitalium

Grinding Operations
1. Surface-Grinding Operations:

2. Internal-Grinding Operations

3. Horizontal-Spindle Surface Grinder

4. Center less-Grinding Operations

Applications
Sharpening of cemented carbide tools
Surgical needles, other thin wall tubes, and fragile parts
Advantages
Deplating removes 95%, and abrasives remaining 5%
of metal Removal - grinding wheel

Disadvantages
High capital costs, because of the special wheel
tool. Power consumption is quite high.
Electrolyte is corrosive.
Limitations
The work material must be conductive.
Nit suitable for machining soft material.
 Require dressing tools for preparing the wheels.

PROF.M.S.MODI
Electron beam machining

Introduction
• Electron Beam Machining is the metal removal process by a
high velocity focused stream of electrons which heats,
melts and vaporizes the work material at the point of
bombardment.
• The production of free electrons is obtained from thermo-
electronic cathodes wherein metal are heated to the
temperature at which the electrons acquire sufficient speed
for escaping to the space around the cathode.
• The acceleration of the electrons is carried by an electric
field while the focusing and concentration are done by
controlled magnetic fields.
PROF.M.S.MODI

• The kinetic energy of a beam of free electrons is
transformed into heat energy as a result of the interaction
of the electrons with the work piece material.
• EBM is a THERMO-ELECTRIC process.
PROF.M.S.MODI

Principal Process
• A beam of electrons is emitted from the electron gun
which is basically following three points.
• A cathode which is a hot tungsten filament (2500o
C)
emitting high negative potential electrons.
• A grid cup negatively based with respect to the filament.
• An anode which is heats at ground potential, and through
which the high velocity electrons pass.
• The gun is supplied with electronic current from a high
voltage D.C source.
PROF.M.S.MODI

• The flow of electrons is controlled by the negative bias
applied to the grid cup.
• The electron passing through the anode is accelerated to
two-third of the velocity of light by applying 50kv to
100kv at the anode, and this speed is maintained till they
strike the work piece.
• Due to the pattern of the electrostatic field produced by
the grid cup, the electrons are focused and made to flow
in the form of a converging beam through a hole in the
anode.
PROF.M.S.MODI

• A magnetic deflection coil is used to make the
electron beam circular having a cross-sectional
diameter of 0.01 to 0.02 mm and deflect it
anywhere.
• A built –in microscope with a magnification of 40
on the work piece enables the operator to accurately
locate the beam impact and observe the actual
machining operation.
• As the beam impacts on the work piece surface the
kinetic energy of high velocity electrons is
immediately converted into the thermal energy and
it vaporized the material at the spot of its impact.
PROF.M.S.MODI

• The power density being very high (about 1.5 billion
w/cm3) it takes a few microseconds to melt and vaporize
material on impact.
• The process is carried out in repeated pulses of short
duration may range from 1 to 16,000 Hz and from 4 to
64,000 microseconds.
PROF.M.S.MODI

Process – Parameters
• The accelerating voltage
• The beam current
• Pulse duration
• Energy per pulse
• Power per pulse
• Lens current
• Spot size
• Power density
PROF.M.S.MODI

Advantage
• Suitable for automatic machining.
• Absence of mechanical contact between work piece and
tool.
• Capability of making very small holes and slots with high
precision, in a short time in any material.
PROF.M.S.MODI

Disadvantage
• High cost of equipment.
• Slow production rate because of slow metal removal rate
and time required to evacuate the chamber.
• Limited application due to
a) Small metal removal rate.
b) Vacuum chamber limits the size of the work piece.
• Skill operators are required.
PROF.M.S.MODI

Application
• EBM has been used to perforate holes in glass fibber
spinning head made from a heat resistant supper alloy.
• Slotting and related milling operations are economically
practical with EBM technology.
• It is used foe thin materials for micro-machining.
PROF.M.S.MODI

PROF.M.S.MODI
Laser Beam Machining

•A laser is a device which is built on the principles of
quantum mechanics to create a beam of light where all of
the photons are in a coherent state - usually with the same
frequency and phase a device that produces a nearly
parallel, nearly monochromatic, and coherent beam of light
by exciting atoms and causing them to radiate their energy
in phase.
•Laser beam machining (LBM) uses the light energy from a
laser to remove material
PROF.M.S.MODI

Applications
• Lasers are being used for a variety of industrial
applications, including heat treatment, welding, and
measurement, as well as a number of cutting operations
such as drilling, slitting, slotting, and marking operations.
Drilling small-diameter holes is possible, down to 0.025
mm. For larger holes, the laser beam is controlled to cut
the outline of the hole.
• The range of work materials that can be machined by
LBM is virtually unlimited including metals with high
hardness and strength, soft metals, ceramics, glass,
plastics, rubber, cloth, and wood.
PROF.M.S.MODI

PROF.M.S.MODI
LBM- WORKING PRINCIPAL OF LASER

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