Specific Machining Process

8/3/2019 Specific Machining Process

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SPECIFIC MACHINING PROCESS

SAHRIJAN AHMAD


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COURSE OUTCOME

At the end of chapter student can,

Explain specific concept of ignitionerosion/electro discharge machining(EDM) andelectro chemical machine.

Describe the basic principle for EDM process andexplain the function of: AC supply source,

servo motor,

servo control,

ignition generator circuit,

electrical pump and electrical tank


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COURSE OUTCOME

Type of material for electrical fluid for EDM

Deionised water,

Mineral oil

White spirit

kerosene


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COURSE OUTCOME

Describe the faraday laws for electrolysis

Name the electro discharge machine(ECM)

equipment

Explain the function of

DC

Supply source

Electrolyte pump

Mist collector


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COURSE OUTCOME

Explain the type of electrode and electrolyte

for the ECM.

Describe the basic principle of electro

chemical grinder and state the rules/safety

precaution procedure for the EDM and ECM

process.


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Non-traditional machining


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ELECTROCHEMICAL MACHINING


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Electrochemical Machining

Reverse of electroplating An electrolyte acts as a current carrier and high electrolyte

movement in the tool-work-piece gap washes metal ions away

from the work piece (anode) before they have a chance to

plate on to the tool (cathode).

Tool generally made of bronze, copper, brass or stainless

steel.

Electrolyte salt solutions like sodium chloride or sodium

nitrate mixed in water.

Power DC supply of 5-25 V.


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Advantages of ECM

Process leaves a burr free surface.

Does not cause any thermal damage to the parts.

Lack of tool force prevents distortion of parts.

Capable of machining complex parts and hard materials

ECM systems are now available as Numerically Controlled

machining centers with capability for high production, high

flexibility and high tolerances.


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ELECTROCHEMICAL GRINDING


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Electrochemical Grinding (ECG)

Combines electrochemical machining with conventionalgrinding.

The equipment used is similar to conventional grinder except

that the wheel is a rotating cathode with abrasive particles.

The wheel is metal bonded with diamond or Al oxide

abrasives.

Abrasives serve as insulator between wheel and work piece. A

flow of electrolyte (sodium nitrate) is provided for

electrochemical machining.

Suitable in grinding very hard materials where wheel wear can

be very high in traditional grinding.


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ELECTRICAL DISCHARGE MACHINING


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Electrical discharge machining (EDM)

Based on erosion of metals by spark discharges. EDM system consist of a tool (electrode) and work piece,

connected to a dc power supply and placed in a dielectric

fluid.

when potential difference between tool and work piece ishigh, a transient spark discharges through the fluid, removing

a small amount of metal from the work piece surface.

This process is repeated with capacitor discharge rates of 50-

500 kHz.


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dielectric fluid mineral oils, kerosene, distilled and deionized

water etc.

role of the dielectric fluid1. acts as a insulator until the potential is sufficiently

high.

2. acts as a flushing medium and carries away the debris.

3. also acts as a cooling medium. Electrodes usually made of graphite.

EDM can be used for die cavities, small diameter deep

holes,turbine blades and various intricate shapes.


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WIRE EDM


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Wire EDM

This process is similar to contour cutting with a band saw. a slow moving wire travels along a prescribed path, cutting

the work piece with discharge sparks.

wire should have sufficient tensile strength and fracture

toughness. wire is made of brass, copper or tungsten. (about 0.25mm in

diameter).


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function of: AC supply source-

servo motor

The servo motors are controlled by microprocessorwhich measures the gap voltage. By monitoring thegap voltage, the servo motor maintains the propergap for spark erosion. If the gap voltage is too high servo motor will retract the electrode. when the gapvoltage is reduce-servo motor advance the electrode

servo control,

ignition generator circuit,

electrical pump and electrical t

Specific Machining Process

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