CHAPTER 1
INTRODUCTION
1.1
TECHNOLOGICAL DEVELOPMENT
As we are in the era of fastest growing technological development and
advancement in manufacturing technology we need quick and better results.
Non conventional machining processes enable us to get consistency and
accuracy in our desired manufacturing techniques.
In the field of engineering, development of such techniques has lead to
revolution in the field of manufacturing. Tasks which are assumed to be
impossible in past can be done within fraction of seconds. Machining of many
metals which needed too much time and used to be too laborious are now
simplified and easied.
1.2
NON-TRADITIONAL MACHINING
However development of newer methods has always been the endeavour of
engineering personnel and scientists. The main ideas behind such
endeavours have generally been the economic considerations, replacements
of existing manufacturing methods by more efficient and quicker ones,
achievement of higher accuracies and quality of surface finish, adaptability of
cheaper materials in place of costlier ones and developing methods of
machining such materials which cannot be easily machined through the
conventional methods etc. Of all this reasons, the last one has contributed
considerably to the post-war developments in machining methods, particularly
because of the use of a large number of hard to machine materials in the
modern industry. A few of such materials are tungsten, hardened and
stainless steel, inconel, uranium, beryllium and some high strength steel
alloys. The increasing utility of such materials in the modern industry has
forced research engineers to develop newer machining methods, so as to
have full advantage of these costly materials.
The use of such costly and hard-to-machine material is quite common in
aircraft industry, research equipment, nuclear plants, missile technology,
sophisticated equipments, manufacturing industries etc. To meet the needs
of such industries, whereas on one hand newer materials have been
developed at the same time a number of newer machining methods have
been evolved for machining of these materials. These machining methods
are known as Unconventional or Non-traditional Machining Methods.
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However there are some common parameters to be taken into consideration
for selecting a particular process like:
Physical properties of the work material,
Type of operation required,
Shape and size required to be produced,
Process capabilities & process economy.
In non-conventional machining methods, there is no direct contact between
the tool and the workpiece; hence the tool needs not be harder than the job.
Further, in spite of the recent technical advancements, the conventional
machining processes are inadequate to produce complex geometrical shapes
in the hard and temperature resistant alloys and die steels. Keeping these
requirements into mind, a number of non-conventional methods have been
developed. These new technological processes can be classified into various
groups as given below:
1.2.1 Mechanical Processes
In mechanical processes, metal removal takes place either by the mechanism
of simple shear or by erosion mechanism where high velocity particles are
used as transfer media and pneumatic/hydraulic pressure acts as a source of
energy. It includes ultrasonic machining (USM), water jet machining (WJM),
abrasive jet machining (AJM), etc.
1.2.2 Thermal Processes
Thermal processes involve the application of very thin intense local heat. Here
melting or vaporization from the small areas at the surface of the workpiece
removes material. The source of energy used is amplified light, ionized
material and high voltage. Examples are laser beam machining (LBM), ion
beam machining (IBM), plasma arc machining (PAM), and electric discharge
machining (EDM).
1.2.3 Electro-chemical Processes
Electro-chemical processes involve removal of metal by the mechanism of ion
displacement. High current is required as the source of energy, and
electrolyte acts as transfer media. It includes electro-chemical machining
(ECM), electro-chemical grinding (ECG), etc.
1.2.4 Chemical Processes
Chemical processes involve the application of resistant material (acidic or
alkaline in nature) to certain portion of the work surface. The desired amount
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of material is removed from the remaining area of the workpiece by the
subsequent application of an etching that converts the workpiece material into
a dissolvable metallic salt. It includes chemical machining (CHM) and
photochemical machining (PCM).
Table 1.1 Classifications of Advanced Machining Processes [1]
Type of
energy
Mechanism
of metal
removal
Mechanical
Transfer
media
Energy source
Processes
Erosion
High velocity
particles
Pneumatic/hydr
aulic pressure
AJM, USM,
WJM
Shear
Physical
contact
Cutting tool
Conventional
machining
Electroche
mical
Ion
displacement
Electrolyte
High current
ECM, ECG
Chemical
Ablation
relation
Reactive
environment
Corrosive agent
CHM
Thermoele
ctric
Fusion
Hot gases
electrons
Ionised material
high voltage
IBM, PAM,
EDM
Vaporisation
Radiation
Amplified Light
LBM
Ions stream
Ionised material
PAM
AJM
Abrasive jet machining
IBM
Ion beam machining
CHM
Chemical machining
LBM
Laser beam machining
ECG
Electrochemical grinding
PAM
Plasma machining
ECM
Electro chemical machining
USM
Ultrasonic machining
EDM
Electric discharge machining
WJM
Water jet machining
Non-traditional machining methods are also classified based on media for
energy transfer like high velocity particles, physical contact, reactive
atmosphere, electrolyte, hot gases, electrons, radiation etc., mechanism of
metal removal like erosion, shear, chemical ablation, ionic dissolution,
vaporisation, spark erosion etc. & source of energy like pneumatic pressure,
hydraulic pressure, corrosive agent, high current, high voltage, ionised gas
etc. Classification of advance machining processes is shown in Table 1.1.
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