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Dept. of Electrical & Electronics Engg.

Electric Discharge MachineElectric Discharge Machine

By,

Mr. Swagat Nanda

EEE, E/07/48

Technical Seminar for 7th Semester

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Table of ContentsTable of Contents1.Introduction to tool room.2.3.Electrical Cutting Technology.4.

5.Electric Discharge Machine (EDM).6.7.Important Terms.8.9.Working of EDM.10.11.Advantages.12.13.Limitations.14.15.Conclusion.


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Tool Room Technology The tool room is the basic requirement of any industry whether it is a smallscale industry or a steel plant.

It is a shop where all the cutting and other operations are done.

The machines employed in tool room are Lathe, Shaper, Cutting machineslike EDM etc.


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Electric Cutting TechnologyElectric Cutting Technology The process of using electricity in cutting has been done since the inceptionof the industrial revolution.

This technology is mainly based on the principle of corona discharge.

Various machines using this technology include the electric discharge machine


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EDMq This is a machine used in cutting materials by the process of corona dischargeq

q

q The material removal from the work piece occurs by a series of rapidlyrecurring current discharges between the two electrodes, separated by a dielectrifluid and subject to electric voltage.

q In an EDM, the cutter acts as an anode and the work piece acts as cathode.q

q

q Now-a-days, EDMs are also embedded with computer software for automaticoperation known as CNC EDM.


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Picture This !!!!!!!!!!Picture This !!!!!!!!!!


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Important Terms

Anode:The positive terminal of an electrolytic cell or battery. In EDM,incorrectly applied to the tool or electrode.

Barrel effect:In wire EDM, a condition where the centre of the cut iswider than the entry and exit points of the wire, due to secondarydischarges caused by particles being pushed to the centre by flushingpressure from above and beneath the work piece.

Cathode:The negative terminal in an electrolytic cell or battery. InEDM incorrectly applied to the work piece.


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ContinuedColloidal suspension:Particles suspended in a liquid that are too fine tosettle out. In EDM, the tiny particles produced in the sparking action form acolloidal suspension in the dielectric fluid.

Duty cycle:The percentage of a pulse cycle during which the current is turnedon (on time), relative to the total duration of the cycle.

Plasma:A superheated, highly ionized gas that forms in the discharge channeldue to the applied voltage.

Dielectric strength:In EDM, the electrical potential (voltage) needed to breakdown (ionize) the dielectric fluid in the gap between the electrode and thework piece.


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Cut Section view of a traditional EDM

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Various EDM tools

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Working of an EDMv Firstly the work piece and the required cutting tools are placed in their requirepositions.

v Then the switch is turned on and the high current electric discharge flowsthrough the cutting tools and the cutting operation starts.

v Until the required shape and the depth of cut are attained, the operationcontinues.

v Wired EDM is a special kind which uses brass wire as a cutting tool.


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Characteristics of work piece


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AdvantagesAdvantages The shape and depth of cut of the work piece is very accurate.

As accuracy is more, the wastage is work piece materials is very less.

CNC EDMs are used mainly in cutting materials used in turbines, Aircrafts etcwhere there is no room for error.

The overall reliability of the work shop increases with such machines.

The time taken by an EDM to cut a work piece is very less compared to lathemachine etc.


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LimitationsLimitations

Initial costs are very high.

Cost of Installation is very high compared to other machines.

It is only used to cut materials which are good conductor of electricity.

Non-metals and other stuff couldnt be cut with EDM.

Highly sophisticated coolants are used which are costly.


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ConclusionConclusionAn EDM is a machine which not only increases the reliability but also used as

a tool for prosperous development of an industrial tool room. It uses the

concepts of lean manufacturing and helps reduce the wastes generated in a

tool room. Recent developments in this machine like the computer numerical

control (CNC) and other computer software is making the machine more

convenient to use although the costs are very high.


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Thank You !!!Thank You !!!


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Any Queries ???Any Queries ???


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