3. TOPICS
Unconventional machining Process – Need – classification –
merits, demerits and applications. Abrasive Jet Machining –
Water Jet Machining – Abrasive Water Jet Machining –
Ultrasonic Machining. (AJM, WJM, AWJM and USM).
Working Principles – equipment used – Process parameters –
MRR- Applications.
4. Conventional Machining Processes
4
• In conventional machining processes, metal is
removed by using some sort of tool which is
harder than the workpiece and it is subjected
to wear.
• Tool and workpiece are in direct contact
13. Need for Unconventional Machining
13
• Greatly improved thermal, mechanical and chemical properties of modern
materials – Not able to machine thru conventional methods. (Why???)
• Ceramics & Composites – high cost of machining and damage caused during
machining – big hurdles to use these materials.
• In addition to advanced materials, more complex shapes, low rigidity structures
and micro-machined components with tight tolerances and fine surface finish
are often needed.
• To meet these demands, new processes are developed.
• Play a considerable role in aircraft, automobile, tool, die and mold making
industries.
14. Need for Unconventional Machining
14
• Very high hardness and strength of the material. (above 400 HB.)
• The work piece is too flexible or slender to support the cutting or grinding
forces.
• The shape of the part is complex, such as internal and external profiles, or
small diameter holes.
• Surface finish or tolerance better than those obtainable conventional process.
• Temperature rise or residual stress in the work piece are undesirable.
20. 20
Chemical & Electrochemical Based Processes
ECM - Electro –Chemical Machining
ECD - Electro Chemical Deburring
ECG – Electro –Chemical Grinding
ECH – Electro – Chemical Honing
21. 21
Thermal Based Processes
LBM - Laser Beam Machining
PAM – Plasma Arc Machining
EBM - Electron Beam Machining
IBM – Ion Beam Machining
22. Mechanical based Unconventional Processes
22
USM – Through mechanical abrasion in a
medium (solid abrasive particles
suspended in the fluid)
WJM – Cutting by a jet of fluid
AWJM – Abrasives in fluid jet.
IJM – Ice particles in fluid jet.
Abrasives or ice – Enhances
cutting action.
27. Chemical & Electrochemical
based Unconventional Processes
27
CHM – uses Chemical
dissolution action in
an etchant.
ECM – uses Electrochemical
dissolution action in
an electrolytic cell.
29. PROCESS SELECTION
29
Based on the following points
1. Physical Parameters
2. Shapes to be machined
3. Process Capability or Machining Characteristics
4. Economic Considerations
43. ADVANTAGES
of UCM
43
• High Accuracy and surface finish in process
• Less Rejected pieces
• Increase productivity
• Tool material need not be harder than work piece
material.
• Easy to machine harder and brittle materials
• There is no residual stresses in the machined material
50. CONSTRUCTION AND WORKING OF AJM
Construction:
• It consists of mixing chamber, nozzle, pressure gauge, hopper, filter,
compressor vibrating device, regulator, etc.
• The gases generally used in this process are nitrogen, carbon dioxide or
compressed air.
• The various abrasive particles are aluminum oxide, silicon carbide, glass
powder, dolomite and specially prepared sodium bicarbonate Aluminum oxide
(A12,O3,) is a general-purpose abrasive and it is used in sizes of 10, 25 and 50
microns. Silicon carbide (SiC) is used for faster cutting on extremely hard
materials.
51. • It is used in sizes of 25 and 50 microns. Dolomite of 200 grit size is found suitable
for light cleaning and etching Glass powder of diameter 0.30 to 0.60 mm are used
for light polishing and deburring.
• As the nozzle is subjected to a great degree of abrasion wear, it is made up of hard
materials such as tungsten carbide, synthetic sapphire (ceramic), etc., to reduce the
wear rate.
• Nozzles made of tungsten carbide have an average life of 12 to 20 hours whereas
synthetic sapphire nozzle have an average life of 300 hours. Nozzle tip clearance
from work is kept at a distance of 0.25 to 0.75 mm.
• The abrasive powder feed rate is controlled by the amplitude of the vibration of
mixing chamber. A pressure regulator controls the gas or air flow and pressure. To
control the size and shape of the cut, either the workpiece or the nozzle is moved by
a well-designed mechanism such as cam mechanism, pantograph mechanism, etc.
52. Working:
• Dry air or gas (N2, or CO₂) is entered into the compressor through a
filter where the pressure of air or gas is increased.
• The pressure of the air varies from 2 kg/cm² to 8 kg/cm²
• Compressed air or high-pressure gas is supplied to the mixing
chamber through a pipe line. This pipe line carries a pressure gauge
and a regulator to control the air or gas flow and its pressure.
• The fine abrasive particles are collected in the hopper and fed into
the mixing chamber. A regulator is incorporated in the line to control
the flow of abrasive particles.
53. • The mixture of pressurized air and abrasive particles from the mixing chamber
flows into the nozzle at a considerable speed.
• Nozzle is used to increase the speed of the abrasive particles and it is increased
up to 300 m/s.
• This high-speed stream of abrasive particles from the nozzle, impact the
workpiece to be machined. Due to repeated impacts, small chips of material get
loosened and a fresh surface is exposed.
• A vibrator is fixed at the bottom of the mixing chamber. When it vibrates, the
amplitude of the vibrations controls the flow of abrasive particles.
54. • This process is widely used for machining hard and brittle materials, non-
metallic materials (germanium, glass, ceramics and mica) of thin sections.
This process is capable of performing drilling, cutting, deburring, etching
and cleaning the surfaces.
• Abrasive Jet Machining (AJM) process differs from sand blasting process.
AJM is basically meant for metal removal with the use of small abrasive
particles, whereas the sand blasting process is a surface cleaning process
which does not involve any metal cutting.
55. Construction details
.
Gas
Used
Nitrogen , Carbon di-oxide ,
compressed air
Abrasive Particles
Used
Aluminium oxide
(10,25&50microns)
Silicon Carbide(25&50microns)
Glass Powder , Dolomite and
Specially Prepared sodium
bicarbonate
Nozzle
Tungsten Carbide ,
Synthetic Sapphire (Ceramic)
67. Abrasive Grain Size
• The various abrasive particles used in AJM process are aluminum oxide
(A12,O3,). silicon carbide (SiC), glass powder, dolomite and specially
prepared sodium bicarbonate Aluminum oxide is a general-purpose
abrasive and is used in sizes of 10, 25 and 50 microns.
• Silicon carbide is used for faster cutting on extremely hard materials. It is
used in sizes of 25 and 50 microns. Dolomite of 200 grit size is found
suitable for light cleaning and etching Glass powder of 0.30 to 0.60 mm are
used for light polishing and deburring.
• In general, larger sizes are used for rapid removal rate while smaller sizes
are used for good surface finish and precision as shown in Fig.
74. Advantages
1. We can cut all kind of materials
2. No heat produced in process , so no thermal damage
3. Very thin and brittle material can be machined
4. Low initial investment
5. Good Surface Finish
6. Intricate holes can be cut in hard and brittle material
75. Dis-Advantages
1. Low MRR
2. Soft Material cannot be machined
3. Machining accuracy is poor
4. Nozzle Wear Rate is High
5. Abrasive Powder cannot be reused
6. Embedding of Abrasive particle in work piece is the high
damage thing in this process
7. It requires Dust Collection System
83. .
.
Nozzle
Used to Increase the velocity of water jet
Made up of Sintered Diamond, Tungsten Carbide and
Synthetic Sapphire
Nozzle Exit Diameter 0.05 – 0.35mm
Velocity of Water Jet From Nozzle 920 m/s
115. Transducer
convert the high
frequency
electrical energy
into Mechanical
Vibrations
Oscillator convert the
Low frequency electrical
energy into high
frequency electrical
energy
20 – 30 HZ
Vibrations are
transferred to
tool material
Abrasive Slurry
Passed
Between the
vibrating tool
and work piece
The
refrigeration
system used
to cool the
abrasive
slurry to 5 –
6 Degree
celcius
119. MAGNETOSTRICTIVE TRANSDUCER
.
Change in length is independent of
the direction of the magnetic field
But depend only on the
magnitude of the field and
Nature of the material
121. MAGNETOSTRICTIVE TRANSDUCER
LT battery used to
heat the filament
So electrons are
produced
Those electrons
are accelerated
by HT Battery
So AC current
Produced in the
circuit
122. So Rod start
to vibrate
due to
magnetostric
tive effect
This vibrations rod
create Ultrasonic
Waves , which sent out
MAGNETOSTRICTIVE TRANSDUCER
124. Resonance
Frequency of the
oscillatory circuit
Frequency of Vibrating
Rod
=
Resonance will occur when
At resonance , the rod vibrates vigorously and ultrasonic
waves are produced at high frequencies
129. Definition - Piezoelectric
• Piezoelectric transducers are a type of electro
acoustic transducer that convert the electrical
charges produced by some forms of solid
materials into energy.
• The word "piezoelectric" literally means
electricity caused by pressure.
132. Working LT battery used to
heat the filament
So electrons are
produced
Those electrons are
accelerated by HT Battery
So AC current
Produced in the
circuit
This AC current Passes
through L1 and L2 and
its transferred to
Secondary circuit
This AC current passed to the plates A and B and it make the
Crystal to vibrate due to the principle of inverse piezoelectric
effect. The vibrations of crystal creates Ultrasonic waves
134. Advantages – Piezoelectric transducer
Disadvantages – Piezoelectric transducer
1. Piezoelectric quartz is high cost
2. Cutting and shaping of crystal is very complex.
146. Abrasive material
It Depend on
1.The type of material to be machined
2. Requirement of Surface finish
For Machining - Tungsten Carbide
- Die Steel
Boron Carbide
Silicon Carbide
Abrasives
For Machining - Glass
- Ceramics
Aluminium oxide
152. Process Parameters
Wear Ratio
1.5 : 1 For Tungsten Carbide Work Pieces
100 : 1 For Glass Work Pieces
50 : 1 For Quartz Work Pieces
75 : 1 For Ceramics
1 : 1 For Hardened tool steel Work Pieces