electro discharge machining

Electrical Discharge Machining is also called or known as Spark machining, spark eroding, burning, die sinking, wire burning or wire erosion.

This is a manufacturing operation in which we used to make desired shapes by using an electrical spark.

This spark near to 8000 to 12000º C.

Electro Discharge Machining
This is how an electro-discharge machine looks like. (By NezzerX at English Wikipedia – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=9740429)

Definition of Electro Discharge Machining:

Electrical Discharge machining is the process of metal removal from the work surface due to an erosion of metal caused by electric spark discharge between the two electrodes tool (cathode) and the work (Anode).

Parts of Electro Discharge Machining:

An Electro Discharge Machine consists of:

  • DC pulse Generator
  • Voltmeter
  • Ammeter
  • Tool
  • Die electric fluid
  • Pump 
  • Filter
  • Servo Controlled Feed
  • Fixtures 
  • Table

1. DC Pulse Generator:

This is a power source for the machining operation. DC power is supplied.

2. Voltmeter:

We know that the voltmeter measures the voltage. Here in this device the same for use.

3. Ammeter:

It measures or checks the flow of the current. If Ammeter is not connected we might not see or check current is flowing or not.

4. Tool:

A tool is connected to negative sources of power whereas the workpiece is connected to positive sources. from the filter, the fluid comes to the tool for the operation.

When Power supply will increase, between tools workpiece the spark generates and then machining starts.

5. Die electric fluid:

It has a property like insulation and we know what insulation means?

Insulation means no current flows from one to another.

The Die electric fluid will be ionized in the form of ion which will help between the tool and workpiece again when power supply stops the fluid comes to its initial position.

6. Pump:

The pump is connected there for sending the fluid to the filter. This works like flowing the fluid from one source to another one.

7. Filter:

As the name indicates the filter, is used to filtrate the different particles like:

In this device, if there is dust particles presence the filter will remove that particle and then it will send to the tool for the operation.

8. Servo controlled feed:

The constant feed will be supplied by the servo for the operation.

9. Fixture:

To hold the table.

10. Table:

To hold the workpiece. 

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Working Principle of Electrical Discharge Machining:

It consists of an electric power supply, the dielectric medium, the tool, workpiece, and servo control.

The workpiece is connected to the positive terminal and the tool is connected to a negative terminal of the DC power supply.

An air gap of 0.005 to 0.05 mm is maintained between the tool and the work.

The die electric fluid which is non-conductor of electricity is forced under pressure through the gap.

When a DC power is supplied, the fluid in the gap gets ionized and produces a spark between the tool and workpiece, causing a local rise in temperature at about 1000 degrees Celsius, when melts the metal in a small area of the workpiece and vaporizes.

The DC supply generates a pulse between 40 to 3000 V and the frequency of spark at the rate of 10000 sparks per second can be achieved.

The electric and magnetic fields on heated metal cause a compressive force which removes the metal from the work surface.

The die electric fluid acts as a coolant carry the cooled metal from the work surface.

The die electric fluid acts as a coolant carries the eroded metal particles which are filtered regularly and supplied back to the tank.

A servomechanism is used to feed the tool continues to maintain a constant gap between two electrodes.

The accuracy of about 0.005 mm can be achieved in this process.

1. A pulse generator (DC). 2 Workpiece. 3 Fixture. 4 dielectric fluid. 5 Pump. 6 Filter. 7 Tool holder. 8 Spark. 9 Tool.
(By Frank50 s – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=41589672)

Applications of Electro Discharge Machining:

These are some of the applications of Electro discharge machining:

  • Drilling for micro holes in the nozzle.
  • This is used in thread cutting.
  • Used in wire cutting.
  • Rotary form cutting.
  • Helical profile milling.
  • Curved hole drilling.
  • Engraving operation on harder materials.
  • Cutting off operation.
  • The shaping of alloy steel and tungsten carbide dies.

Advantages of Electrical Discharge Machining:

Here are some advantages of Electro discharge machining:

  • It can be used for any hard material and even in the heat-treated condition.
  • Any complicated shapes made on the tool can be reproduced.
  • High accuracy of about 0.005 mm can be achieved.
  • Good surface finish can be achieved economically up to 0.2 microns.
  • Machining time is less than the conventional machining process.
  • No mechanical stresses are developed in this process (There is no contact between tool and work)
  • Higher tool life due to proper lubrication and cooling.
  • Hard and erosion resistant surface on the dies can be developed easily.
  • It can be applied to any electrically conductive materials.

Disadvantages of Electrical Discharge Machining:

Electro discharge machining still has some disadvantages and those are:

  • Excessive tool wear.
  • High power consumption.
  • The sharp corner cannot be reproduced.
  • High heat developing causing the change in metallurgical properties of materials.
  • The workpiece must be an electrical conductor.
  • Surface cracking may take place in some materials.
  • Redressing of a tool is required for deep holes.
  • Over-cut is formed.
  • Difficult finding expert machinists.

So today we have learned about the Definition, Working Principle, Application, Advantages, Disadvantages of electro-discharge machining. Feel free to ask your doubts in the comment section, we are here to help you.

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What are the applications of EDM?

1. Drilling for micro holes in the nozzle.
2. This is used in thread cutting.
3. Used in wire cutting.
4. Rotary form cutting.
5. Helical profile milling.

What is EDM?

Electrical Discharge machining is the process of metal removal from the work surface due to an erosion of metal caused by electric spark discharge between the two electrodes tool (cathode) and the work (Anode).

What does an EDM machine do?

This is a manufacturing operation in which we used to make desired shapes by using an electrical spark.

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About the Author

Amrit Kumar

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Amrit is a Co-founder of Learn Mechanical Portal (Previously owned "Engramritkumar.com"). He completed his diploma in Mechanical Engineering from Acharya Polytechnic Bangalore and also completed his B-Tech from Delhi.

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