3. Machining Process
Manufacturing processes can be broadly divided into
two groups:
a)
b)
Primary manufacturing processes : Provide basic
shape and size
Secondary manufacturing processes : Provide final
shape and size with tighter control on dimension,
surface characteristics
Material removal processes once again can be
divided into two groups
1.
2.
3
Conventional Machining Processes
Non-Traditional Manufacturing Processes or non-
conventional Manufacturing processes
5. Needs for Non Traditional Machining
•
•
•
•
•
•
5
Extremely hard and brittle materials or Difficult to
machine materials are difficult to machine by
traditional machining processes.
When the work piece is too flexible or slender to
support the cutting or grinding forces.
When the shape of the part is too complex.
Intricate shaped blind hole - e.g. square hole of 15
mmx15 mm with a depth of 30 mm
Deep hole with small hole diameter - e.g. φ 1.5 mm
hole with l/d = 20
Machining of composites.
6. Conventional Machining VS Unconventional Machining
In Conventional machining process, the cutting
tool and work piece are always in physical
contact, with a relative motion against each
other, which results in friction and a significant
tool wear.
In Unconventional machining processes, there
is no physical contact between the tool and
work piece. Although in some non-traditional
processes tool wear exists, it rarely is a
significant problem.
6
7. Outline of AJM
Definition
Schematic Diagram of AJM
Typical AJM parameters
Applications
Limitations
Advantages
Disadvantages
Video of Cutting Process
7
8. Definition of AJM :-
In AJM, the material removal takes place due to
impingement of the fine abrasive particles. These
particles move with the high speed air (or gas)
stream.
The abrasive particles are typically of 0.025 mm
diameter and the air discharges at a pressure of
several atmosphere.
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10. Working of Abrasive jet machining: (AJM):
The nozzle is made of a hard material like
Tungsten Carbide here fine grained abrasive
particles are fed from the Hooper into the
mixing chamber.
High pressure air is forced in to the mixing
chamber.
The stream of abrasive particles bombards the
work piece at a very high speed and removes
the work material due to erosion.
The abrasive particle feed rate is controlled by
the amplitude of vibration of the mixing
chamber.
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11. Typical AJM Parameters
Abrasive
Aluminum oxide for Al and Brass.
SiC for Stainless steel and Ceramic
Bicarbonate of soda for Teflon
Glass bed for polishing.
Size
10-15 Micron
Quantity
5-15 liter/min for fine work
10-30 liter/min for usual cuts.
50-100 liter/min for rough cuts
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12. Typical AJM Parameters
Medium
Dry air, CO N
2, 2
Quantity: 30 liter/min
Velocity: 150-300 m/min
Pressure: 200-1300 KPa
Nozzle
Material: Tungsten carbide
Stand of distance: 2.54-75 mm
Diameter: 0.13-1.2 mm
Operating Angle: 60° to vertical
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13. Typical AJM Parameters
Factors affecting MRR:
Types of abrasive and abrasive grain size
Flow rate
Stand off distance
Nozzle Pressure
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14. Nozzle
The nozzle is one of the most vital elements
controlling the process characteristics. Since it is
continuously in contact with the abrasive grains
flowing at a high speed, the material must be
hard to avoid any significant wear.
One of the most important factors in AJM is the
distance between the work surface and the tip of
the nozzle, normally called the nozzle distance
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16. Applications:-
For drilling holes of intricate shapes in hard and
brittle materials
For machining fragile, brittle and heat sensitive
materials.
AJM can be used for drilling, cutting, deburring,
cleaning and etching.
Micro-machining of brittle materials
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17. Limitations:-
MRR (Material removal rate) is rather low
(around ~ 15 mm^3/min for machining glass).
Abrasive particles tend to get embedded
particularly if the work material is ductile.
Tapering occurs due to flaring of the jet.
Environmental load is rather high.
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18. Advantages:-
Extremely fast setup and programming.
No start hole required.
There is only one tool.
Low capital cost.
Less vibration.
No heat generation in work piece.
Environmentally Friendly.
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21. Outline of LBM
Definition
Schematic Diagram of LBM
Working of LBM
Applications
Limitations
Advantages
Disadvantages
Video of Cutting Process
21
22. Definition of LBM :-
Laser-beam machining is a thermal material-
removal process that utilizes a high-energy,
coherent light beam to melt and vaporize
particles on the surface of metallic and non-
metallic work pieces.
Lasers can be used to cut, drill, weld and mark.
LBM is particularly suitable for making accurately
placed holes.
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23. Principle of Laser beam machining (LBM):
Conversion of electrical energy into heat energy
to emit laser beam energy.
Laser beam is focused on lance then create high
energy the high energy concentration on work
piece then work piece is melt and vaporized of
metal.
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24. Working of LBM
The diagram of LBM is
shown in figure.
Laser is stand for Light
Amplification by
Simulated Emulsion of
Radiation.
The work piece is
placed on the
aluminum work table
which material is hard
not cut by laser beam.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
25. Working of LBM
Ruby rod is used into
form of cylindrical
crystal both ends of
ruby rod are finished to
optical tolerance.
The flash lamp wound
around the ruby rod
and connected to
power supply.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
26. Working of Laser beam machining (LBM):
The ruby rod becomes high efficient on low
temperature and low efficient on high
temperature. It is thus continuous cooled with
water, air or liquid nitrogen.
When the light beam has been amplified
sufficiently and intensity beam of light comes out
form partially reflected end it is focused on the
work piece at the focused very high temperature
which vaporized and removes the metal on work
piece.
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27. Applications:-
LBM can make very accurate holes as small as
0.005 mm in refractory metals ceramics, and
composite material without warping the work
pieces.
It is used for welding of thin metal sheet.
Leaser can be used for cutting as well as drilling.
Heat treatment.
It is used for cutting complex profile.
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28. Limitations:-
Uneconomic on high volumes compared to
stamping
Limitations on thickness due to taper
High capital cost
High maintenance cost
Assist or cover gas required
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29. Advantages:-
Very hard and abrasive material can be cut.
Sticky materials are also can be cut by this
process.
It is a cost effective and flexible process.
High accuracy parts can be machined.
No cutting lubricants required
No tool wear
Narrow heat effected zone
No contact between tool and work piece.
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30. Disadvantages:-
Investment cost is more.
Skilled operator is required.
Operating cost is more.
Flash lamp life is too short.
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31. Summary:-
Mechanics of material removal : Melting, Vaporization
Medium : Normal atmosphere
Tool : Higher power laser beam
Maximum material removal rate: 5 mm^3/min
Specific power consumption : 1000 W/mm^3/min
Materials application : All materials
Shape application : Drilling fine holes
Limitations : Very power consumption, cannot cut
materials with high heat conductivity and high reflectivity
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34. Principle of EDM:
Electrical discharge machining (EDM), sometimes also
referred to as spark machining, spark
eroding, burning, die sinking, wire burning or wire
erosion, is a manufacturing process whereby a desired
shape is obtained using electrical discharges (sparks).
Material is removed from the work piece by a series of
rapidly recurring current discharges between two
electrodes , separated by a die-electric liquid and
subject to an electric voltage. One of the electrodes is
called the tool-electrode, or simply the "tool" or
"electrode", while the other is called the workpiece-
electrode, or "workpiece".
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35. Working of EDM
The diagram of electro
discharge machining shown
in figure.
EDM is thermal erosion
process whereby material is
melted and vaporized from
an electrically conductive
work piece immerse in a
liquid dielectric with a series
of spark discharge between
the tool electrode and the
work piece created by a
power supply.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
36. Working of EDM
The electrode and the work
piece are separated by a
dielectric medium.
The dielectric medium is like
as kerosene, paraffin or light
oil.
The strong electrostatic field
between the electrode and
work piece produce
emission of electrons from
the cathode.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
37. Working of EDM
In this gap between tool
and work piece get
ionized. The liquid is force
to sparking zone.
Due to high temperature,
the metal at the sparking
zone melts
instantaneously.
The material of the tool is
usually a material which
conduct electricity and
which can be easily
shaped.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
38. Advantages:-
Smaller holes can be easy machined.
No contact between tool and work piece then tool
life is increase.
Any complex shape can be machined.
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40. Summary:-
Mechanics of material removal : Electrolysis
Medium : Conducting electrolyte
Tool : Cu, Brass, Steel
Gap : 50-300 µm
Maximum material removal rate: 15*10^3 mm^3/min
Specific power consumption : 7 W/mm^3/min
Materials application : All conducting metals and alloys
Shape application : Blind complex cavities, curved
surfaces, through cutting, large through cavities
Limitations : High speed energy consumption, not
applicable with electricity non-conducting materials
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43. Principle of Ultrasonic machining(USM):
In this method with the help of piezoelectric
transducer tool is vibrate at high frequency in a
direction normal to the surface being machined
abrasive slurry are used for the remove the metal
from work piece.
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44. Working of USM
The USM diagram shown
in figure.
In ultrasonic machining a
tool vibrate longitudinally
at 20 to 30 kHz with
amplitude between 0.01
to 0.06 mm is pressed on
to the work surface with
light force.
The electronic oscillator
and amplifier is also
known as generator.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
45. Working of USM
It converts the
electrical energy of low
frequency to high
frequency.
At the time high
frequency current is
passed through the
coil therefore change
in electromagnetic field
which produces
longitudinal strain.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
46. Working of USM
As the tool vibrate with
specific frequency the
abrasive slurry mix with
water and grain of definite
proportion is made to flow
under pressure through
the tool work piece
interface. The flow of slurry
through the work tool
interface actually causes
thousand of microscopic
grain to remove the work
material by abrasion.
May 23, 2017
47. Applications:-
USM is best suitable for hard, brittle material,
such as ceramics, carbides, glass, precious
stone etc.
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48. Advantages:-
Any materials can be machined regardless of
their electrical conductivity.
Especially suitable for machining of brittle
materials.
Machined parts by USM possess better surface
finish and higher structural integrity.
USM does not produce thermal, electrical and
chemical abnormal surface.
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49. Disadvantages:-
Tool wears fast in USM.
Machining area and depth is restraint in USM.
High cost of tooling.
MMR is low.
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50. Summary:-
Mechanics of material removal : Brittle fracture caused by
impact of abrasive grains due to tool vibrating at high
frequency.
Medium : Slurry
Tool : Soft Steel
Gap : 25-40 µm
Frequency : 15-30kHz
Amplitude : 25-100 µm
Specific power consumption : 1000 W/mm^3/min
Materials application : Metals and alloys, semiconductors,
non- metals
Shape application : Round and irregular holes
Limitations : Very low mrr, tool wear, depth of holes and
cavities small May 23, 2017
52. Definition of EBM :-
Electron Beam Machining (EBM) is a thermal
process. Here a steam of high speed electrons
impinges on the work surface so that the kinetic
energy of electrons is transferred to work
producing intense heating.
Depending upon the intensity of heating the work
piece can melt and vaporize.
The process of heating by electron beam is used
for annealing, welding or metal removal.
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53. EBM:
During EBM process very high velocities can be
obtained by using enough voltage of 1,50,000 V
can produce velocity of 228,478 km/sec and it is
focused on 10 - 200 μM diameter.
Power density can go up to 6500 billion
W/sq.mm. Such a power density can vaporize
any substance immediately.
Complex contours can be easily machined by
maneuvering the electron beam using magnetic
deflection coils
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54. EBM:
To avoid a collision of the accelerating electrons
with the air molecules, the process has to be
conducted in vacuum. So EBM is not suitable for
large work pieces.
Process is accomplished with vacuum so no
possibility of contamination.
No effects on work piece because about 25-
50μm away from machining spot remains at
room temperature and so no effects of high
temperature on work
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55. Working of EBM
The EBM beam is
operated in pulse mode.
This is achieved by
appropriately biasing the
biased grid located just
after the cathode.
Switching pulses are
given to the bias grid so
as to achieve pulse
duration of as low as 50
μs to as long as 15 ms.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
56. Working of EBM
Beam current is directly
related to the number of
electrons emitted by the
cathode or available in
the beam.
Beam current once
again can be as low as
200μ amp to 1 amp.
Increasing the beam
current directly
increases the energy
per pulse.
<slide Title> | CONFIDENTIAL 2011 May 23, 2017
57. Working of EBM
Similarly increase in pulse duration also
enhances energy per pulse.
High-energy pulses (in excess of 100 J/pulse)
can machine larger holes on thicker plates.
A higher energy density, i.e., for a lower spot
size, the material removal would be faster though
the size of the hole would be smaller.
The plane of focusing would be on the surface of
the work piece or just below the surface of the
work piece.
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58. Applications:-
Used for producing very small size holes like
holes in diesel injection nozzles, Air brakes etc.
Used only for circular holes.
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59. Limitations:-
Material removal rate is very low compared to
other convectional machining processes.
Maintaining perfect vacuum is very difficult.
The machining process can’t be seen by
operator.
Work piece material should be electrically
conducting.
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60. Advantages:-
Very small size holes can be produced.
Surface finish produced is good.
Highly reactive metals like Al and Mg can be
machined very easily.
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61. Summary:-
Mechanics of material removal : Melting, Vaporization
Medium : Vacuum
Tool : Beam of electron moving at very high velocity
Maximum material removal rate: 10 mm^3/min
Specific power consumption : 450 W/mm^3/min
Materials application : All materials
Shape application : Drilling fine holes, cutting contours in
sheets, cutting narrow slots
Limitations : Very high specific energy consumption,
necessity of vacuum, expensive machine
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