Briefly description about Wire cut EDM

1. BY
Partha Tripathy
Nitesh Kumar
Mahtab Alam
MECHANICAL ENGINEERING
NETAJI SUBHASH ENGINEERING COLLEGE
Guided By:
Prof. Pradip Kumar Pal

3.  Thermal Removing Techniques
 HISTORY OF EDM
 Introduction
 EDM Working principle
 Important characteristic
 Working
 Advantages
 Disadvantages
 Application
 Wc-edm
 Working principle
 Important characteristics

4.  Major components
 Wire cut EDM Process
 Advantages
 Disadvantages
 Application

5.  In thermal removing processes, thermal
energy, provided by a heat source, melts
and/or vaporizes the volume of the material to
be removed.
 Among thermal removal methods, electrical
discharge machining or EDM is the oldest and
most widely used.

6.  In1770s, discovered by Joseph Priestly.
 Developed in the mid 1970s
 In the mid 1980s, the EDM techniques were
transferred to a machine tool

7. ELECTRICAL DISCHARGE MACHINING
(EDM)
 The servo control unit is provided to
maintain the predetermined gap.
 It senses the gap voltage and compares it
with the present value and the difference
in voltage is then used to control the
movement of servomotor to adjust the
gap.
Important Characteristics of EDM:
 Tool Material : Copper, brass and
graphite.
 Work piece material : Conducting
materials and alloys.
 Process parameters : Voltage,
Capacitance, spark gap, melting
temperature of work.
 Material Removal : Melting and
vaporization.

8. WORKING :
 A suitable gap between the tool and the work piece is
maintained to cause the spark discharge.
 The gap can be varied to match the machining conditions
such as MRR.
 As soon as the voltage gradient set up between the tool and
the work piece is sufficient enough to break down the
dielectric medium.
 A conducting electrical path is developed for spark
discharge owing to ionization of the fluid medium and
thereby causes the current flow

9.  The temperature of the spot hit by the
spark may rise up to 10000 deg celsius
causing the work surface to melt and
vaporize and ultimately to take the
form of sphere as it is quenched by the
surrounding fluid.
 If the tool is fed downwards,
maintaining the predetermined gap,
the tool shape profile will be
reproduced on the work piece.
 The spark gap generally 0.01 to 0.1
mm.
 Higher gap increases the discharge
energy but decreases the spark
frequency.

10. ADVANTAGES:
1. Machining time is less than the conventional
machining process.
2. Any completed shape that can be made on the tool can be reproduced
on the work piece.
3. The process can be employed for extremely hardened work piece.
4. The process can be applied to all electrically conducting metals and alloys
irrespective of their melting points.
5. Brittle and slender work pieces can be machined with out distortion.
6. Considerably easier and more economical polishing can be done on the
catering type surfaces developed by EDM.
7. Fine holes can be easily drilled.
8. Enables high accuracy on tools and dies ,because they can be machined
in as hard condition.

11. DISADVANTAGES :
 It can not be applied to non conducting materials.
 Power required is very high compared to conventional machining
processes.
 In some materials surface cracking may take place.
 Sharp corners can not be produced.
 Material removal rate is low.
 Surface tends to be rough for larger removal rates.

12. APPLICATIONS :
 Very useful in tool manufacturing due to ease with which hard metals
and alloyed can be machined.
 Resharpening of cutting tools and broaches, trepanning of holes with
straight of curved axes.
 Machining of cavities for dies and re-machining of die cavities without
annealing.

13.  Electrical discharge machining wire cutting (EDM-
WC) is a thermal mass-reducing process that uses a
continuously moving wire to remove material .
 A thin wire of brass, tungsten or copper is used as an
electrode.
 Deionized water is used as the dielectric.
 With wire edm one can basically cut out any
design.

14. THE WORKING PRINCIPLE IS BASED
ON THERMOELECTRIC ENERGY. THIS
ENERGY IS CREATED BETWEEN WORK
PIECE AND TOOL.

16.  In this process, a thin metallic wire is fed on-to
the work piece, which is submerged in a tank
of dielectric fluid such as deionized water.
 The wire, which is constantly fed from a spool,
is held between upper and lower diamond
guides. The guides are usually CNC-controlled.
 In the wire-cut EDM process, water is
commonly used as the dielectric fluid. Filters
and de-ionizing units are used for controlling
the resistivity and other electrical properties.
 Wires made of brass are generally preferred.

17.  The area where in discharge takes place gets
heated to very high temperatures such that the
surface gets melted and removed. The cut particles
(debris) get flushed away by the continuously
flowing dielectric fluid and keep the wire and
workpiece cool.
 The wire and workpiece must be electrically
conductive.
 Schematic illustration of the wire EDM process. As
much as 50 hours of machining can be performed
with one reel of wire, which is then discarded.
 Pieces over 16 in thick can be machined.

18. 1. CNC :
Process is controlled by CNC.
2. Power supply :
Provide energy to the spark.
3. Mechanical section :
worktable,workstand,wire drive mechanism.
4. Dielectric system:
The water reservoir where filtration , condition
of water(resistivity/conductivity)and
temperature of water is provided and
maintained.

19.  Tool material : brass, tungsten or copper
 Work piece material :conducting material and alloys.
 Process parameters : Pulse on time, Pulse off time,
Pulse peak voltage, spark gap and melting
temperature of work.
 Material removal : Melting and vaporization
 Wire diameter : 0.25mm
 Kerf width : 0.41mm
 Die electric flushing pressure : ( 10
-15 kgf/𝑐𝑚2 )
 Spark gap : (kerf width –wire dia)/2 mm

21.  Machining accuracy is higher.
 As the cutting path is very small, there is very
less removal ratio of material.
 During machining, electrode wire doesn’t
touch work piece, there is no physical cutting
force.
 There is very little heat impact on the surface of
work piece
 It can machine small shape holes, small gap or
job with complicated shape.
ADVANTAGES

22.  Consumes high levels of energy
 Only able to machine conductive materials.
 More expensive process than conventional
milling or turning.

23.  Aerospace, Medical, Electronics and
Semiconductor applications
 Tool & Die making industries.
 In making Gauges & Cams
 Cutting of Gears
 Manufacturing hard Electrodes.

24. SCOPE AND PLAN FOR THE INVESTIGATION
Scope:
 There are so many process variables involved in wire cut EDM. Each of them
can influence the performance of the process
 Surface finish, accuracy, kerf width material removal rate etc. are expected to
be influenced by these parameters.
 Also change of material of the wire, may change the output responses.
 Wire cut EDM though not very new, is a comparably newer unconventional
machining process.
 Development of the process is still being continuous.
 Extensive research will enrich the science, technology and application of the
process to further extent.
 Among several aspects, identification of the process parameter among many
and their influence on material removal rate, kerf, width is an important aspect,
which need to be investigated.

25. PLAN OF THE PRESENT
INVESTIGATION:
 The effect of a few process variable like pulse on time, pulse off time,
wire feed rate etc. on material removal rate & surface finish & kerf
width will be studied.
 For the above purpose a design of experiment will be made and
experiments will be carried out accordingly.
 The result of the experiments will be studied, interpreted and
analysed.
 Process optimization may also be carried out.
 Effect change of wire material is also in consideration.

26. REFERENCES:
WWW.WIKIPEDIA.ORG
WWW.SCRIBD.COM
WWW.ACCUTEX.COM.
WWW.THOMASNET.COM