Electrical Discharge Machining (EDM): It is also known as Spark Machining or Spark Eroding process.
In this process, electrical energy is used to generate the Spark between the tool and workpiece submerged under the dielectric medium so that material removal takes place from the surface of the workpiece by local melting or Vaporization.
Electrolyte used: Dielectric Fluid (Kerosene).
The dielectric fluid in the normal form acts as insulator whereas at proper voltage or increase in voltage makes the dielectric fluid to be Ionized.
The Optimum gap between the tool and the workpiece is 0.03 mm.
Voltage – 70V
Properties of the Dielectric:
- Low viscosity.
- Remain electrically non-conductive up to the desired voltage breakdown takes place.
- It can act as a good cooling medium.
- It can carry away all the metal particles produced during the spark erosion.
The tool used in the Electric Discharge Machining process is either Copper or Tungsten or Copper-Tungsten Alloy.
Properties Possessed by the Tool:
It must possess high
- Melting Point
- Electrical Conductivity.
MRR(Material Removal Rate):
Out of all the non-traditional machining methods, the Electric Discharge Machining will remove more material. In the sense, the MRR is higher for EDM.
Diagram of Electrical Discharge Machining Process:
The Electrical Discharge Machining(EDM) setup consists of
- Fixture: To hold the table.
- Table: To hold the workpiece.
- Dielectric Medium
- Feed unit (Servo Feed Unit)
- Power supply.
Working of Electrical Discharge Machining(EDM) Process:
The workpiece is fixed in the dielectric container by means of a fixture.
The tool is fed up by the Servo Feed Unit which can move downward in a vertical direction.
The power supply is given to the electrical discharge machining process I.e. Positive terminal is given to the workpiece and Negative terminal is given to the tool.
The tool and workpiece are separated by means of dielectric fluid and an optimum gap is maintained between them.
As stated above, that at normal conditions, the dielectric fluid acts as an insulator. In the sense, no electrical conductivity is taking place.
But, by an increase of high pressure, the dielectric fluid ionizes into Negative and Positive Ions.
The positive ions are attracted towards negative ions and negative ions are attracted towards positive ions and thereby the heat is generated.
When positive and negative ions collide with each other then the spark is generated between the tool and workpiece which can remove the material from the surface of the workpiece.
When there is no Spark in the container, then the dielectric fluid again turns as an insulator.
The same procedure is repeated to remove the material from the surface of the workpiece.
This is the detailed explanation of Electrical Discharge Machining process along with the basic terms and working.
Advantages of EDM:
- The machining process does not depend on the mechanical properties of the workpiece.
- No residual stresses will be generated because no forces are acting.
- The deeper hole is possible to produce (L/D) up to 20.
- Out of all the non-traditional machining methods, EDM is the method with higher Material Removal Rate (MRR).
- Surface finish is better due to melting and vaporization.
Limitations of EDM:
- Workpiece material must be electrically conductive.
- Perfect square corner holes are not possible to produce.
- Hardening of the workpiece is taking place near to the hole.
Applications of EDM:
- It is used for producing hole size less than 0.1 mm
- Used for die sinking or die manufacturing.
- holes in the air brakes or Pneumatic Brakes were done by an electrical discharge machining process.
This is the detailed explanation of Electric Discharge Machining process with basic terms, diagram, working, advantages, limitations, and applications were explained in a detailed manner.
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