PRESENTATION

ON

ELECTRIC DISCHARGE MACHINING

Presented by:

Alok kumar (75114003)

Md. Shahnawaz khan (75114031)

Principle of EDM

Electric discharge machining (EDM), sometimes also

referred to as spark machining, spark eroding, burning,

die sinking, wire burning or wire erosion, is a

manufacturing process whereby a desired shape is

obtained using electrical discharges (sparks).

Material is removed from the workpiece by a series of

rapidly recurring current discharges between two

electrodes, separated by a dielectric liquid and subject to

an electric voltage. One of the electrodes is called the

tool-electrode, or simply the "tool" or "electrode", while

the other is called the workpiece-electrode, or

"workpiece"

Mechanism of metal removal

Filter

Charge up an electrode Bring the electrode near a metal

workpiece (oppositely charged).

As the two conductors get close enough a spark will arc

across a dielectric fluid. This spark will "burn" a small

hole in the electrode and workpiece.

Continue steps 1-3 until a hole the shape of the electrode

is formed.

The removal of metal from the workpiece is obtained

by means of energy released by repetitive spark

discharges

EDM Wire cutting

Electrical discharge machining wire cutting (EDM-WC) is a thermal mass-reducing process that uses a continuously moving wire to remove material by means of rapid controlled repetitive spark discharges.

A thin wire of brass, tungsten, or copper is used as an electrode.

A dielectric fluid is used to flush the removed particles, regulate the discharge, and keep the wire and workpiece cool. The wire and workpiece must be electrically conductive.

This process is much faster than electrode EDM.

Advantages and disadvantages:

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.

There is no direct contact between tool and work piece. Therefore

delicate sections and weak materials can be machined without any

distortion.

A good surface finish can be obtained.

very fine holes can be drilled.

Some of the disadvantages of EDM include:

The slow rate of material removal.

Potential fire hazard associated with use of combustible oil based

dielectrics.

The additional time and cost used for creating electrodes for

ram/sinker EDM.

Reproducing sharp corners on the workpiece is difficult due to

electrode wear.

Specific power consumption is very high.

"Overcut" is formed.

Excessive tool wear occurs during machining.

Applications of EDM

Hardened steel dies, stamping tools, wire drawing and extrusion dies, header

dies, forging dies, intricate mould cavities and such parts are made by the EDM

process.

The process is widely used for machining of exotic materials that are used in

aerospace and automatic industries.

EDM being a non-contact type of machining process, it is very well suited for

making fragile parts which cannot take the stress of machining. The parts that fit

such profiles include washing machine agitators; electronic components, printer

parts and difficult to machine features such as the honeycomb shapes.

Deep cavities, slots and ribs can be easily made by EDM as the cutting forces

are less and longer electrodes can be used to make such collets, jet engine blade

slots, mould cooling slots etc.

Micro-EDM process can successfully produce micro-pins, micro-nozzles and

micro-cavities.