The document discusses electro discharge machining (EDM), a machining method used for hard, electrically conductive metals. EDM works by using electrical sparks to erode unwanted material away from a workpiece. This allows machining of metals that other techniques cannot cut. The document covers the history of EDM's development, how the process works using sparks and a dielectric fluid, and different EDM techniques like wire EDM and spark EDM as well as their applications and advantages/disadvantages.

3. 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.

4. WHAT IS EDM ?
Electro Discharge Machining
Used on hard metals
Works with electrically
Conductive materials

5. 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.

7. ACCESSORIES
 Surface plate
 Sine plate
 Slip gauge
 Dial indicator
 Magnetic ‘V’ block
 Precision vise
 Pin gauge set
 Tooling ball set
 Special holders

8. BASIC OF E D M
 Workpiece
 Electrodes
 Sparks
 Dielectric fluid
Deionized water
Dielectric oil
 Cutting speed

10. HOW EDM WORKS?
 Uses very powerful sparks (~3x106 V/m)
 Series of rapidly recurring
Charges
 Electroerosion
 Remove excess by fluid
Flow

11. SPARKS
 The phenomena “Breakdown”
occurs
 A path for the current through
dielectric
 Locally 10-15.000 ºC Ionize the
fluid
 Metal melts or vaporizes

12. WIRE EDM
 Needs wire feed
o Pre hole is required
for machining for passing
the wire
o Wire dia + spark gap is the
kerf

13. Applications for wire edm
 Gears, splines
 Machining of carbide
 Cone shape angle profiles
 Prototype production

14. Advantages Disadvantages
 handles delicate tasks
 highly accurate
 very small kerf for wire
EDM
 produces complex
shape
deep, or 3-D shapes
o wire wear out
oslow cutting rates
o heat affected local
stress formation.
oBlind holes can not be
produce

15. Spark EDM
oElectrode required
oSize of electrode +spark gap
is the kerf

16. Applications for spark
edm
 Slots, keyways, square & hex drives ,Gears
 Small or deep holes, especially in hardened
material
 Removal of broken taps and drills
 Hardened jobs can be tapped (cnc edm)
 Machining of carbide

17. Advantages Disadvantages
 handles delicate tasks
 may cut or drill very
hard materials
 highly accurate
 produces complex
shape
deep, or 3-D shapes
o electrode wear
oslow cutting rates
o heat affected local
stress formation.