ELECTRIC DISCHARGE MACHINING

ELECTRICAL DISCHARGE
MACHINING
MATERIALS SCIENCE AND
TECHNOLOGY II PRESENTATION
ASENA DENİZ DEMİRCAN
UFUK OKUMUŞ
SEMA AŞIK

WHAT IS EDM?
 Electrical Discharge Machining
 Used on hard metals
 works with electrically
conductive materials

HISTORY OF EDM
 In1770s, discovered by Joseph Priestly.
 Developed in the mid 1970s
 In the mid 1980s, the EDM techniques were
transferred to a machine tool
 Today,it is a viable technique that helped shape
the metal working industry.

ACCESSORIES
 surface plate
 surface gage
 sine plate
 gage block set
 pin gage set
 dial indicator
 drop indicators
 precision vise
 tooling ball set
 and various electrode
holders

BASIC DEFINITIONS
 Workpiece
 Sparks
 Electrodes
 Dielectric liquid
Deionized water
Dielectric oil
 Cutting speed
 Accuracy

TYPES OF EDM
 Wire Machining  Ram Machining
Other EDM Processes
•Electrical Discharge Milling
•Electrical Discharge Grinding
•Electrical Discharge Dressing
•Ultrasonic Aided EDM
•Abrasive Electrical Discharge
Grinding
•Micro Electrical Discharge
Machining
•Micro Wire EDM
•Mole EDM
•Double Rotating Electrodes EDM

WHEN TO USE EDM
 Where deep cutting is required
 In unattended cutting
 For high-expertise parts
 Where EDM finish is specified
 For hard materials
 For sharp inside corners
 For the most complex geometry

HOW EDM WORKS?
 Uses very powerful sparks (~3x106 V/m)
 Series of rapidly recurring
charges
 electroerosion
 Remove excess by fluid
flow
http://lawww.epfl.ch/webdav/site/la/users/139973/public/photo-
project/electroerosion.gif

SPARKS
 The phenomena “Breakdown”
occurs
 A path for the current through
dielectric
 Locally 10-15.000 ºC
 Ionize the fluid
 Metal melts or vaporizes
http://www.scienceclarified.com/images/uesc_04_img0212.jpg

PULSING SPARKS
 Periodically striking ( >100.000 sparks/sec)
 More accurate machining
 Controlling the on-off time for optimization
On time Off time
http://www.reliableedm.com/Complete%20EDM%20Handbook/Complete%20EDM%20Handbook_9.pdf

MOVING THE TOOL
 CNC control (computer numerical controlled)
 Enable 3D movement
 Not neccessary
in all types
 Very important in
wire EDM
http://www.huadongmould.com/userfiles/image/des1.jpg

 Wire EDM for detailed
shapes
 Sinker EDM for dies
(mold) industry
http://www.erodatoolsltd.co.uk/images/examples/mould.jpg
http://www.todaysmachiningworld.com/wp-
content/uploads/2010/10/hiwwire-465x600.jpg

WIRE EDM
 Needs wire feed
 Can work overnight
 Impossible to have
narrower gap than the
wire
 Can be close to wire
diameter
http://www.new.manufacturinget.com/wp-content/uploads/2009/04/picture7.jpg

 Voltage changes with
distance
 Distance must be
controlled
 Manufacturer
programs do all the
work
 Promising method
with oscilloscope
http://www.new.manufacturinget.com/wp-content/uploads/2009/04/picture1.jpg

TOOL EROSION (WEAR)
 Tool is also eroded
 It can be replaced (wire
feed)
 Affects the shape of
workpiece
 Can be proceed with
negative-piece
 Reverse polarity
electoplating
 Deposits the eroded
graphite back
http://robotroom.com/Rust-Removal/Graphite-carbon-electrodes-used-in-EDM.jpg

EDM IS A MACHINING METHOD
TYPICALLY USED FOR HARD METALS
WHICH ARE ELECTRICALLY CONDUCTIVE.
IT MAKES POSSIBLE TO WORK WITH
METALS FOR WHICH TRADITIONAL
MACHINING TECHNIQUES ARE
INEFFECTIVE.

 EDM can be used to make fixtures, collets and jet
engine blade slots, mold cooling ribs and
reinforcing ribs. This fact makes wire and ram
EDMs ideal for making magnetic reader heads
for missiles, artificial joints, turbine blades and
car engine prototypes (bgpeck)
Engine Turbine Blades

APPLICATIONS
 Prototype production
The EDM process is most widely used by the
mould-making tool and die industries, but is
becoming a common method of making prototype
and production parts,especially in the aerospace,
automobile and electronics industries in which
production quantities are relatively low.
 Metal disintegration machining
Several manufacturers produce EDM machines
for the specific purpose of removing broken tools
(drill bits or taps) from work pieces. In this
application, the process is termed "metal
disintegration machining".

COINAGE DIE MAKING
This type of EDM is usually performed
submerged in an oil-based dielectric. The finished
object may be further refined by hard (glass) or
soft (paint) enameling and/or electroplated with
pure gold or nickel. Softer materials such as
silver may be hand engraved as a refinement.
Master at top, badge die
workpiece at bottom,oil
jets at left (oil has been
drained).Initial flat
stamping will be"dapped"
to give a curved surface.

 Small hole drilling
On wire-cut EDM machines, small hole
drilling EDM is used to make a through hole in a
workpiece in through which to thread the wire for
the wire-cut EDM operation. A separate EDM
head specifically for small hole drilling is
mounted on a wire-cut machine and allows large
hardened plates to have finished parts eroded
from them as needed and without pre-drilling.
A blade with internal cooling as applied in the high-
pressure turbine

EXAMPLES OF USE
 Slots, keyways, square & hex drives
 Gears, splines
 Small or deep holes, especially in hardened
 Removal of broken taps and drills
 Hard tapping
 Machining of carbide
 Application of textured surface finish

EXAMPLE APPLICATIONS OF WIRE EDM
Miniature Parts
0.002 Diameter Wire — Internal Gear

Titanium Needles
Example of Stacking Work Pieces

EXAMPLE APPLICATIONS OF WIRE EDM
7min(Ra) surface finish
without isolated tooling
Precision Die Matching

ADVANTAGES AND DISADVANTAGES
 EDM is a method of machining parts that cannot be done
by conventional machines.
 “Since the tool does not touch the workpiece, there are no
cutting forces generated; therefore, very fragile parts can
be machined” .
 The shape and also the hardness of the materials being
used make EDM ideal.

SOME OF THE ADVANTAGES OF EDM INCLUDE
MACHINING OF:
 Complex shapes that would otherwise be difficult
to produce with conventional cutting tools
 Extremely hard material to very close tolerances
 Very small work pieces where conventional
cutting tools may damage the part from excess
cutting tool pressure.

SOME OF THE ADVANTAGES OF EDM
INCLUDE MACHINING OF:
 Intricate & complex details are possible
 Internal corners down to R .001" [.025mm]
 Small features down to .004" [.10mm]
 Very high accuracy attainable
 Precise control of surface finish
 No cutting forces
 Virtually no geometric limitations

SOME OF THE DISADVANTAGES OF EDM
INCLUDE:
 The slow rate of material removal.
 The additional time and cost used for creating
electrodes for ram/sinker EDM.
 Specific power consumption is very high.
 Power consumption is high.

ADVANTAGES AND DISADVANTAGES OF EDM
VERSUS TRADITIONAL MACHINING
 handles delicate tasks
 may cut or drill very
hard materials
 highly accurate
 very small kerf for
wire EDM
 produces complex,
deep, or 3-D shapes
 no burrs
 electrode wear
 slow cutting rates
 thin, brittle heat-
affected zone
Advantages Disadvantages

REFERENCES
 ^ a b Theoretical models of the electrical
discharge machining process. III. The variable
mass, cylindrical plasma model
 ^ Singh, A. & Ghosh, A. A Thermo-Electric
Model of Material Removal During Electric
Discharge Machining. International Journal of
Machine Tools Manufacture 39, 669-682 (1999).
 ^ a b c d e Jameson, 2001.
 ^ Semon, 1975.
 http://www.advantageedm.com/examples.asp

REFERENCES
 ^ Fuzhu Han, Li Chen, Dingwen Yu and Xiaoguang
Zhou. Basic study on pulse generator for micro-edm.
The International Journal of Advanced
Manufacturing Technology 33, 474-479 (2007). doi:
10.1007/s00170-006-0483-9 URL:
http://www.springerlink.com/content/e40q854g2r5ku9
00/
 ^ a b c d e Carlo Ferri, Atanas Ivanov and Antoine
Petrelli. Electrical measurements in μ-edm. Journal
of Micromechanics and Microengineering 18, 085007+
(2008). doi:10.1088/0960-1317/18/8/085007 URL:
http://www.iop.org/EJ/abstract/0960-
1317/18/8/085007/ e-print, i.e. author-created un-
copyedited version.

ELECTRIC DISCHARGE MACHINING

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ELECTRIC DISCHARGE MACHINING