This document provides an overview of ultrasonic machining (USM). It explains that in USM, a tool oscillated at ultrasonic frequencies (around 20 kHz) with abrasive particles in the gap between the tool and workpiece. The abrasive particles are forced to repeatedly impact the work surface due to the ultrasonic oscillations, removing material through micro-chipping. Key advantages of USM include the ability to machine hard and brittle materials precisely without producing thermal or chemical defects, while disadvantages include low material removal rates and fast tool wear. Common abrasives used include aluminum oxide and silicon carbide in a water slurry. USM is suitable for machining intricate shapes, small holes, and hard non-conductive

1. Presented By
Prof.S.Sathishkumar
Assistant Professor
Department of Mechanical Engineering
Vel Tech (Engineering College)
Avadi-Chennai-62
UNCONVENTIONAL MACHINING PROCESS
UNIT-2 As per Anna University Syllabus

2. *
Manufacturing processes can be broadly divided into two groups:
a) primary manufacturing processes : Provide basic shape and size
b) 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. Conventional Machining Processes
2. Non-Traditional Manufacturing Processes or non-conventional
Manufacturing processes
Conventional Machining Processes mostly remove material in the form
of chips by applying forces on the work material with a wedge shaped
cutting tool that is harder than the work material under machining
condition.

3. *
The major characteristics of conventional machining are:
• Generally macroscopic chip formation by shear deformation
• Material removal takes place due to application of cutting forces –
energy domain can be classified as mechanical
• Cutting tool is harder than work piece at room temperature as well
as under machining conditions
Non-conventional manufacturing processes is defined as a group of
processes that remove excess material by various techniques
involving mechanical, thermal, electrical or chemical energy or
combinations of these energies but do not use a sharp cutting tools as
it needs to be used for traditional manufacturing processes.
The major characteristics of Non-conventional machining are:
1. Material removal may occur with chip formation or even no chip
formation may take place. For example in AJM, chips are of
microscopic size and in case of Electrochemical machining material
removal occurs due to electrochemical dissolution at atomic level.

4. *
The major characteristics of Non-conventional machining:
2. In NTM, there may not be a physical tool present. For example in laser
jet machining, machining is carried out by laser beam. However in
Electrochemical Machining there is a physical tool that is very much
required for machining
3. In NTM, the tool need not be harder than the work piece material. For
example, in EDM, copper is used as the tool material to machine
hardened steels.
4. Mostly NTM processes do not necessarily use mechanical energy to
provide material removal. They use different energy domains to provide
machining. For example, in USM, AJM, WJM mechanical energy is
used to machine material, whereas in ECM electrochemical dissolution
constitutes material removal.

5. *
classification of NTM processes is carried out depending on the nature of energy
used for material removal.
1. Mechanical Processes
 Abrasive Jet Machining (AJM)
 Ultrasonic Machining (USM)
 Water Jet Machining (WJM)
 Abrasive Water Jet Machining (AWJM)
 2. Electrochemical Processes
 Electrochemical Machining (ECM)
 Electro Chemical Grinding (ECG)
 Electro Jet Drilling (EJD)
3.Chemical Processes
 Chemical Milling (CHM)
 Photochemical Milling (PCM)
4. Electro-Thermal Processes
 Electro-discharge machining (EDM)
 Laser Jet Machining (LJM)
 Electron Beam Machining (EBM)

6. *
• 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.

7. *
In Abrasive Jet Machining (AJM), abrasive particles are made to impinge on the
work material at a high velocity. The high velocity abrasive particles remove the
material by micro-cutting action as well as brittle fracture of the work material.

8. *
In AJM, generally, the abrasive particles of around 50 μm grit size
would impinge on the work material at velocity of 200 m/s from a
nozzle of I.D. of 0.5 mm with a stand off distance of around 2 mm.
The kinetic energy of the abrasive particles would be sufficient to
provide material removal due to brittle fracture of the work piece or
even micro cutting by the abrasives.

9. *
AJM set-up

10. *
Process Parameters and Machining Characteristics
Abrasive : Material – Al2O3 / SiC
Shape – irregular / spherical
Size – 10 ~ 50 μm
Mass flow rate – 2 ~ 20 gm/min
Carrier gas : Composition – Air, CO2, N2
Density – Air ~ 1.3 kg/m3
Velocity – 500 ~ 700 m/s
Pressure – 2 ~ 10 bar
Flow rate – 5 ~ 30 lpm
Abrasive Jet : Velocity – 100 ~ 300 m/s
Mixing ratio – mass flow ratio of abrasive to gas
Stand-off distance – 0.5 ~ 5 mm
Impingement Angle – 600 ~ 900
Nozzle : Material – WC
Diameter – (Internal) 0.2 ~ 0.8 mm
Life – 10 ~ 300 hours

11. Typical AJM Parameters
*Factors affecting MRR:
*Types of abrasive and abrasive grain size
*Flow rate
*Stand off distance
*Nozzle Pressure

12. *
effect of process parameters on MRR

13. *

14. *
Modeling of material removal
Material removal in AJM takes place due to brittle fracture of the work
material due to impact of high velocity abrasive particles.
Modeling has been done with the following assumptions:
(i) Abrasives are spherical in shape and rigid. The particles are
characterized by the mean grit diameter
(ii) The kinetic energy of the abrasives are fully utilised in removing
material
(iii) Brittle materials are considered to fail due to brittle fracture and
the fracture volume is considered to be hemispherical with diameter
equal to chordal length of the indentation
(iv) For ductile material, removal volume is assumed to be equal to the
indentation volume due to particulate impact.

16. Advantages of AJM
 Low capital cost.
 Less vibration.
 Good for difficult to reach area.
 No heat is genera6ted in work piece.
 Ability to cut intricate holes of any hardness and brittleness in the material.
 Ability to cut fragile, brittle hard and heat sensitive material without damage
Disadvantages of AJM:
 Low metal removal rate.
 Due to stay cutting accuracy is affected.
 Parivles is imbedding in work piece.
 Abrasive powder cannot be reused.

17. Applications of AJM:
 For abrading and frosting glass, it is more economical than acid etching and grinding.
 For doing hard suffuses safe removal of smears and ceramics oxides on metals.
 Resistive coating etc from ports to delicate to withstand normal scrapping.
 Delicate cleaning such as removal of smudges from antique documents.
 Machining semiconductors such as germanium etc.

18. Water Jet Machining Process
&
Abrasive Water Jet Machining

19. *Water Jet Machining
*The water jet machining involves directing a high pressure (150-1000 MPa) high
velocity (540-1400 m/s) water jet(faster than the speed of sound) to the surface to
be machined. The fluid flow rate is typically from 0.5 to 2.5 l/min
*The kinetic energy of water jet after striking the work surface is reduced to zero.
*The bulk of kinetic energy of jet is converted into pressure energy.
*If the local pressure caused by the water jet exceeds the strength of the surface
being machined, the material from the surface gets eroded and a cavity is thus
formed.
*The water jet energy in this process is concentrated over a very small area, giving
rise to high energy density(1010
w/mm2
) High

20. Setup

21. *Water is the most common fluid used, but additives such as alcohols, oil
products and glycerol are added when they can be dissolved in water to improve
the fluid characteristics.
*Typical work materials involve soft metals, paper, cloth, wood, leather, rubber,
plastics, and frozen food.
*If the work material is brittle it will fracture, if it is ductile, it will cut well:
*The orifice is often made of sapphire and its diameter rangesfrom 1.2 mm to 0.5
mm:

22. Water Jet Equipment's
It is consists of three main units
(i) A pump along with intensifier.
(ii)Cutting head comprising of nozzle and work table movement.
(iii) filter unit for debries,pout impurities.
Advantages
- no heat produced
- cut can be started anywhere without the need for predrilled holes
- burr produced is minimum
- environmentally safe and friendly manufacturing.
Application – used for cutting composites, plastics, fabrics, rubber, wood
products etc. Also used in food processing industry.

23. *Abrasive Water jet machining
*The rate of cutting in water jet machining, particularly while cutting ductile
material, is quite low. Cutting rate can be achieved by mixing abrasive powder in
the water to be used for machining.
*In Abrasive Water Jet Cutting, a narrow, focused, water jet is mixed with
abrasive particles.
*This jet is sprayed with very high pressures resulting in high velocities that cut
through all materials.
* The presence of abrasive particles in the water jet reduces cutting forces and
enables cutting of thick and hard materials (steel plates over 80-mm thick can be
cut).
*The velocity of the stream is up to 90 m/s, about 2.5 times the speed of sound.

25. *Abrasive Water Jet Cutting process was developed in 1960s to cut
materials that cannot stand high temperatures for stress distortion or
metallurgical reasons such as wood and composites, and traditionally
difficult-to-cut materials, e.g. ceramics, glass, stones, titanium alloys

27. WJM - Pure
WJM - with stabilizer
AWJM – entrained – three phase –
abrasive, water and air
AWJM – suspended – two phase –
abrasive and water
 o Direct pumping
 o Indirect pumping
 o Bypass pumping

28. Orifice – Sapphires – 0.1 to 0.3 mm
Focusing Tube – WC – 0.8 to 2.4 mm
Pressure – 2500 to 4000 bar
Abrasive – garnet and olivine - #125 to #60
Abrasive flow - 0.1 to 1.0 Kg/min
Stand off distance – 1 to 2 mm
Machine Impact Angle – 60o to 900
Traverse Speed – 100 mm/min to 5 m/min
Depth of Cut – 1 mm to 250 mm

30. • Extremely fast set-up and programming
• Very little fixturing for most parts
• Machine virtually any 2D shape on any material
• Very low side forces during the machining
• Almost no heat generated on the part
• Machine thick plates
Advantages of AWJM

31. ULTRASONIC MACHINING PROCESS

32. *History
The roots of ultrasonic technology can be traced back to research on the
piezoelectric effect conducted by Pierre Curie around 1880.
He found that asymmetrical crystals such as quartz and Rochelle salt (potassium
sodium titrate) generate an electric charge when mechanical pressure is applied.
Conversely, mechanical vibrations are obtained by applying electrical
oscillations to the same crystals.
Frequency values of up to 1Ghz (1 billion cycles per second) have been used in
the ultrasonic industry.
Today's Ultrasonic applications include medical imaging (scanning the unborn
fetus) and testing for cracks in airplane construction.

33. Ultrasonic Waves
The Ultrasonic waves are sound waves of frequency higher than 20,000 Hz.
Ultrasonic waves can be generated using mechanical, electromagnetic and thermal
energy sources.
They can be produced in gasses (including air), liquids and solids.
Magnetostrictive transducers use the inverse magnetostrictive effect to convert
magnetic energy into ultrasonic energy
This is accomplished by applying a strong alternating magnetic field to certain
metals, alloys and ferrites

34. Principle of Machining
In the process of Ultrasonic Machining, material is removed by micro-chipping or erosion
with abrasive particles.
In USM process, the tool, made of softer material than that of the workpiece, is oscillated
by the Booster and Sonotrode at a frequency of about 20 kHz with an amplitude of about
25.4 um (0.001 in).
The tool forces the abrasive grits, in the gap between the tool and the workpiece, to impact
normally and successively on the work surface, thereby machining the work surface.
 During one strike, the tool moves down from its most upper remote position with a
starting speed at zero, then it speeds up to finally reach the maximum speed at the mean
position.

35. *As the tool continues to move downwards, the force acting on these grits increases
rapidly, therefore some of the grits may be fractured.
*As the tool moves further down, more grits with smaller sizes come in contact with
the tool, the force acting on each grit becomes less.
*Eventually, the tool comes to the end of its strike, the number of grits under impact
force from both the tool and the work piece becomes maximum.
*Grits with size larger than the minimum gap will penetrate into the tool and work
surface to different extents according to their diameters and the hardness of both
surfaces

38. Advantages
 Machining of any material regardless of conductivity.
 Precision machining of brittle hard materials.
 Does not produce electric, thermal or chemical defects at the surface.
 Can drill circular or non-circular holes in very hard materials.
 Less stress because of its non-thermal nature.
Disadvantages
Low material removal rate.
 Tool wears fast.
 Machining area and depth are quite restricted.

39.  Abrasives:
Selection on the type of work-piece material, hardness of work- piece, metal
removal rate, desired surface finish etc.
 Types:
Al2O3, Sic, Boron Carbide etc.
Water slurry with 30 to 60% by volume of abrasive.
 Applications:
1) For machining intricate shaped products.
2) Small holes.
3) Machining of hard and non-conductive material.

41. Thank you
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