DEF
The conventional manufacturing processes are the processes
that use single- or multi-point tools to remove material in the form of
chips.such as turning,
boring, milling, shaping, broaching, slotting, grinding etc
The non-conventional
manufacturing processes are those by which maerial removal accomplished with
electrochemical reaction, high temperature plasmas and
high-velocity jets of liquids and abrasives.such as Water Jet Machining, Electron Beam Machining, Electro-discharge
Machining etc.
PROCESSes.In
non-conventional processes mechanical,thermal and Electricall enegy is used for
shaping,cutting and removal of material under certain conditions.
Charecteristics;
• Material
removal may occur with chip formation or even no chip formation may take place.
• In NTM, mostly no use of physical cutting tool . For
example in laser jet machining, machining is carried out by laser beam.
• 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.
Application;
- Tool manufacturing
- Holes with straight & curved axes
- Applied for the machining of hard and brittle materials like
carbides glass
- Complex cavities
- Intricate shapes
Advantages
•
Surface finish or tolerance better than those obtainable
conventional process.
·
These processes are very much economical for machining very hard
material.
·
Maintain high degree of dimensional accuracy .
·
Highly delicate sections and weak materials can also be processed
without any risk of their distortion.
·
Fine holes can be drilled
easily and accurately.
·
Hardness and toughness of workpiece do not create problems in
machining operation.
Disadvantages;
- Concentrating
heat onto any material greatly affects its microstructure and will
cause cracking, which is not desirable.
- Safety
requirements for thermal methods, especially laser, are demanding in
terms of time and cost.
- Machining
large areas or many surfaces at the same time using thermal methods
is not normally possible.
In contrast, non-traditional manufacturing processes harness
energy sources considered
unconventional by yesterday’s standards. Material removal can
now be
Conventional machining can
be defined as a process using mechanical (motion) energy.
Non-conventional machining
utilises other forms of energy. The three main forms of
energy used in
non-conventional machining processes are as follows :
• Thermal
energy
• Chemical
energy
• Electrical energy
Modern machining methods are also named as non-conventional
machining methods. These methods form a group of processes which removes excess
material by various techniques involving mechanical, thermal, electrical
chemical energy or combination of these energies. There is no cutting of metal
with the help of metallic tool having sharp cutting edge. The major reasons of
development and popularity of modern machining methods are listed below.
(a) Need of machine newly developed metals and non-metals having
some special properties like high strength, high hardness and high toughness. A
material possing the above mentioned properties are difficult to be machined by
the conventional machining methods.
(b) Sometimes it is required to produce
complex part geometries that cannot be produced by following conventional
machining techniques. Non-conventional machining methods also provide very good
quality of surface finish which may also be an encouragement to these methods.
There can be a very long list of non-conventional machining
methods. These methods can be classified as the basis of their base principle
of working.
APPLICATIONS;
Application of
Electric Discharge Machining
This process is highly economical for machining of very hard
material as tool wear is independent of hardness of workpiece material. It is
very useful in tool manufacturing. It is also used for broach making, making
holes with straight or curved axes, and for making complicated cavities which
cannot be produced by conventional machining operations. EDM is widely used for
die making as complex cavities are to be made in the die making. However, it is
capable to do all operations that can be done by conventional machining
Application of WCEDM
WCEDM is similar to hand saw operation in applications with good
precision. It is used to make narrow kerf with sharp corners. It does not
impose any force to workpiece so used for very delicated and thin workpieces.
It is considered ideal for making components for stamping dies. It is also used
to make intricate shapes in punch, dies and other tools.
Applications of USM
This process is generally applied for the machining of hard and
brittle materials like carbides glass, ceramics, precious stones, titanium,
etc. It is used for tool making and punch and die making. The workpeice
material is normally removed in the form of very find chips so generated
surface quality is extremely good. It is widely used for several machining
operations like turning, grinding, trepanning and milling, etc. It can make
hole of round shape and other shapes.
WORKING PRINCIPLE;
Working principle of USM is same as that of conventional
machining that is material of workpiece is removed by continuous abrasive
action of hard particles vibrating in the slurry. Abrasive slurry acts as a
multipoint cutting tool and does the similar action as done by a cutting edge
disadvantages.
• Inconel
718, titanium and other hard metals and alloys have a very high melting
point. Using thermal methods
will require high energy input for these materials.
• Concentrating
heat onto any material greatly affects its microstructure and will
normally cause cracking,
which may not be desirable.
• Safety
requirements for thermal methods, especially laser, are demanding in
terms of time and cost.
• Machining
large areas or many surfaces at the same time using thermal methods
is not normally possible.
Manufacturing
processes can be broadly divided into two groups and they are primary
manufacturing processes and secondary manufacturing processes. The former ones
provide basic shape and size to the material as per designer’s requirement.
Casting, forming, powder metallurgy are such processes to name a few. Secondary
manufacturing processes provide the final shape and size with tighter control
on dimension, surface characteristics etc. Material removal processes are
mainly the secondary manufacturing processes.
Material
removal processes once again can be divided into mainly two groups and they are
“Conventional Machining Processes” and “Non-Traditional Manufacturing
Processes”.
Examples of conventional machining processes are turning,
boring, milling, shaping, broaching, slotting, grinding etc. Similarly,
Abrasive Jet Machining (AJM), Ultrasonic Machining (USM), Water Jet and
Abrasive Water Jet Machining (WJM and AWJM), are some of the Non Traditional
Machining (NTM) Processes.
differences
and similar characteristics between conventional machining processes and NTM
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.
Such forces induce plastic deformation within the work piece leading to shear deformation
along the shear plane and chip formation. Fig. 9.1.1 depicts such chip
formation by shear deformation in conventional machining.
Thus
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
Traditional Machining (NTM) Processes on the other hand are characterised as
follows:
• 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
• 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
• 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.
• 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.
Thus
classification of NTM processes is carried out depending on the nature of
energy used for material removal. The broad classification is given as follows:
• Mechanical Processes
⎯ Abrasive Jet Machining
(AJM)
⎯
⎯ Abrasive Water Jet
Machining (AWJM)
• Electrochemical Processes
⎯ Electrochemical
Machining (ECM)
⎯ Electro Chemical
Grinding (ECG)
⎯ Electro Jet Drilling
(EJD)
• Electro-Thermal Processes
⎯ Electro-discharge machining
(EDM)
⎯ Laser Jet Machining (LJM)
⎯
• Chemical Processes
⎯
Chemical Milling (CHM)
⎯
Photochemical Milling (PCM) etc.
