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P R E S E N T E D B Y,

U M A . B . S

I I S E M M T E C H

( 1 M S 11 M S C 0 1 3 )

D E PA RT M E N T O F M E C H A N I C A L E N G I N E E R I N G

L E C T. M R . M O H A N D A S . K . N

Electric Discharge Machining

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Unit 2: Thermal metal removal process

Principle of operation – Uma. B. S

EDM basic circuitry – Gajaana Anne, Anand Babu

Dielectric fluids, process parameter – Mrudula Prashanth

Benefits, limitations and applications - Manjunath

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Presentation Content

Introduction

Popularity of EDM

Basic principle of EDM

Mechanism of metal removal

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Nontraditional Machining and Thermal Cutting Processes

Nontraditional machining :

Material removal process- mechanical, thermal, electrical or chemical energy

Do not use a sharp cutting tool in the conventional sense

Thermal cutting process :

Thermal energy generally applied to a small portion of the work surface, causing removal by erosion and/or vaporization

Thermal energy is generated by conversion of electrical energy

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EDM highlights

Energy type: Thermal

Mechanics of metal removal: Erosion and/ or vaporization

Energy source: Electric spark

Medium: Dielectric fluid

Spark Gap: 10-125µm

Maximum metal removal rate: 5*10³ mm³/min

Spark frequency: 200-500,000Hz

Peak voltage: 30-250 volts

History In1770s, discovered by Joseph Priestly.

In 1943 first EDM Machine (Lazarenko & Lazarenko)

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

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EDM

7 Electrically conductive materials

Physical properties of w/p not a barrier

(Hastalloys, nimonics, waspalloy) HSTR metals

No mechanical deformation

Surface produced – contains multitude of small craters (helps in oil retention)

Metal removal due to thermal effect – no bulk heating

Process can be automated with less difficulty

Popularity of EDM

8Thermal (Thermoelectric) Processes

EBM - electron beam machining EDM - electrical discharge

machining EDG - electrical discharge

grinding EDWC - electrical discharge wire

cutting LBM - laser beam machining PAM - plasma arc machining Ion beam machining

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ClassificationEDM

Sinking by EDM

Cutting by EDM Grinding by EDM

Drilling

Die sinking

Slicing using ribbon disc

Wire cutting

Slicing using ribbon

External EDM grinding

Internal EDM grinding

Form grinding

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Terms in EDM

Spark - The electrical discharge between two conductors

Spark Gap - The space between the workpiece and the electrode at the point of discharge

Overcut - measurement difference between the dimensions of the cavity EDMed and the dimensions of the electrode used to cut the cavity

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Basic scheme of EDM

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Component of EDM system

EDM system: A tool (electrode) Work piece A dc power supply Servomotor Dielectric fluid

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ExactDifficultMachining

Overall view of workpiece and tool

Detailed view of spark gap

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Principle of operation

Application of an electrical potential between tool (electrode) and workpieceCreation of an ionized channelSparkImplosion of the plasma channelMaterial ejection (Erosion and/or vaporization)

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Mechanism of metal removal

Diagram of electroerosive machining: (1) tool, (2) work-piece, (3) liquid dielectric, (4) electric discharges

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Fig A. Crater formed on the workpieceFig B. The finished EDM workpiece - several distinct

layers

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1. Layer with small globules of removed workpiece metal and electrode

2. the “white” or “recast” layer3. Heat affected zone or annealed layerFig A.

Fig B.

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References

Advanced Machining Processes – V. K Jain (Pg No.,126)

Unconventional Manufacturing process – M. K. Singh (Pg No.,81)

“Manufacturing science ” – Amitabh Ghosh (Pg No., 329)

HMT production technology

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THANK YOU

Questions?