EDM is a recent machining technique used to cut metals which can’t be cut with traditional methods. EDM works with materials of electrical conductivity.

1. Electrical Discharge Machining, Its Principles And
Applications
EDM is a recent machining technique used to cut metals which
can’t be cut with traditional methods. EDM works with materials
of electrical conductivity.
Two primary EDM methods are
 Ram EDM
 Wire EDM
Between the two methods the main difference is based on the
electrodes. In ram EDM graphite electrodes are used, which are
machined in traditional tools and with a special shape it is
connected to the power source. The electrodes are connected
to a ram as well. When the arrangements are done the
electrodes are fed into the work piece. The entire process is
carried out under a submerged fluid bath. In Wire EDM the
electrode is a thin wire. Here processed brass wires are made
use of for putting into the material. Wire EDM is done while
submerged in a bath of water.
Ram Electro-Discharge Machining (EDM) Method:
Rapid spark produced between the two electrodes control the
metal erosion. An appropriate gap is necessary known as spark
gap.
The rate of metal removal is related to the spark gap. If both
the electrodes are of same materials then the highest erosion
takes place on the positive electrode (anode). The two
electrodes are kept apart and distanced by a dielectric fluid. A
transient electric discharge is created across the gap in the
form of spark. With a sufficient potential difference between the
electrodes, the dielectric fluid is ionized and broken down to
produce a conductive spark channel. The current gets
discharged across the channel as spark. If potential difference
is lesser than or equal to 12 volts the dielectric fluid is

2. deionised. The process repeats by its own as the condensers
begins to recharge.
The spark release energy in the form of local heat and a local
temperature found is in the order of 12000°C. Such high
temperature and pressure melts away some metals and little of
which is vaporized and the rest fine material particles get
carried away by the fluid circulating around the electrodes
which create a crater on the w/p.
How to make Tool Material choice?
Many factors are considered while selecting the tool material.
 Lower erosion rate and decent work to tool wear ratio
 electrical conductivity
 good machine ability
 low electrical resistance
 high melting point
 high rate of electron emission
EDM has one drawback and it is wear ratio of the tool.
Tool Wear
While applying EDM the tool or cathode erodes as well and this
is not good. It is unavoidable but limited as the wear of the
cathode is lesser than the anode. This occurs due to the
following:
 Cations from the dielectric fluid strike the cathode but
electrons hit the anode. Though electrons are lighter than
the cations it has more energy and moves with greater
velocity. So anode gets eroded.
 During spark a compressive force is created at the
cathode which lowers the erosion at cathode.
 Fluid medium is made of hydrocarbon. Pyrolysis yield
gases which produce carbon particle and they create a

3. thin layer of protection on the cathode. Hence the cathode
is safer than anode.
Purpose of Dielectric Fluid
 Effective Coolant for the work piece and the tool.
 It works like an insulating material.
 The eroded materials are carried by the medium.
 It is a coolant to quench the spark and prevent an arc.
What you need for dielectric fluid?
 Optimum Viscosity is necessary.
 It must not react with the work piece, container or tool
material.
 Non-expensive, easy availability and inflammable.
 It must not produce toxic gases or vapours during
operation.
 It must be a hydrocarbon.
The various dielectric fluids are: transformer oil, oil, spirit
(white), and kerosene etc
Advantages of EDM
 Any hard or brittle metal which is tough as well can be
machined.
 Harder materials like steel alloys or tungsten carbides and
other non-conventional machining like forging and press
tools can be made.
 Complicated shapes could be yielded.
 Finer holes can be accurately.
 Wear resistance surface could be made because work
pieces produced with EDM have micro-craters which has
lubricants.
 Harder metals can be machined faster compared to their
conventional process.
Disadvantages:
 The power needed is quite higher compared to the
traditional machining. There are chances of surface

4. cracking when the materials become brittle at room
temperature.
 A thin layer ranging from 0.01 mm to 0,10 mm that has 4
% carbon might get deposited on the work pieces made of
steel
 A lower Material Removal Rate in comparison.
 Can’t yield sharp corners.
Applications of EDM
 Used for machining to give intricate shapes and narrow
slots and blind cavities.
 To generate negative tool geometry
 EDM is quite useful for making small holes.
 It is used in air craft engines and brake valves and etc.
Wire Electrical Discharge Machining
It cuts the work piece with electrical discharge. Here either the
work piece or the wire moves. The spark discharge
phenomenon which is used to erode the metal same as the
traditional EDM. Here, the wire acts as an electrode hence
complicated shapes could be cut easily without electrode
formation. Another important part is the distilled water supplier
with a constant specific resistance.
Features of Wire EDM:
 Electrode formation is not necessary.
 Electrode wears is negligible.
 Smooth machine surface.
 Tight dimensional and geometrical tolerances.
 Straight holes can be produced.
 Machine could be operated without regular supervision for
a long time at higher operating rates.
 You don’t need any special skill to run the machine.
Advantages

5.  Due to the absence of the split lines, savings of the stages
in the tools occurs. It allows more punch opening in every
stage.
 No flashes on the moulded parts.
 Necessary for tool manufacturing and storing.
 Work pieces are hardened before cutting.
 Whole work can be done in a machine.
 Very economical.
 Number of rejected work pieces is quite small.
With this I conclude. To know more, keep visiting this space.
At CRB Tech Solutions, we give CAD CAM certification
course in Pune. If you want trainings in methods and
implementation of design processes, you must get a good
knowledge on the concept and the practical knowledge of the
software through our quality and comprehensive CAD/CAM
courses.
If you are looking for an AutoCAD training course, come and
join us. We will guide and support you in improving your skill in
AutoCAD programs and help you grow in this field.
If you are looking for good opportunities in CAD Cam jobs,
then join our CAE Institute in Pune which offers the best
training through our mechanical design engineering
courses.