Electrical Discharge Machining Process | Electrical Discharge Machining Principle |EDM

EDM process is used for cutting complex and precise geometric shapes into electrically conducting metals. The metal electrode and the part are laced very close to each other, separated by a non-conducting liquid (called a dielectric fluid) which creates path for discharge – a commonly used dielectric fluid is kerosene. A voltage difference is then applied to the part and tool, generating a spark; the heat from the spark melts a tiny bit of metal from the part. The melted metal cools and solidifies as tiny particles in the dielectric.

01-edm machines - electrical discharge macining

The metal is carried away by pumping the dielectric to flow, and the process continues. Following major electrodes are used viz; copper, graphite, or gold (very fine gold wire is used to cut profiles into metal parts). Wire type tool is used in EDM process to make the cut profiles, or a negative shape of the required Geometry to be machined, in which case the tool is copper or graphite. Application of focused heat raise the temperature of work piece locally at a particular point, this way melting and evaporation of two metals is done. By this process (EDM), cutting of complex dies and moulds gives feasible solution; the tool shape is the exact negative of the required shape of the part.

EDM Components:

1.  CNC (Computerized Numerical Control ) Machine.

2.  Electric Power Supply ( Provides energy to the spark).

3.  Mechanical Section consists the following: Worktable, work stand, taper unit, and wire drive mechanism.

4. Dielectric System.

01-schematic illustration of EDM process

Principles of EDM:

Electrical Discharge Machining (EDM) is a proscribed metal-removal process which is used to eliminate metal by means of electric spark erosion. In this method an electric sparkle is used as the work tool to erode the workpiece to fabricate the finished part to the preferred shape. The metal-removal process is performed by applying a energetic (ON/OFF) electrical charge of high-frequency current throughout the electrode to the work piece. This erodes very small portions of metal from the work piece at a defined rate.

Types of Electric Discharge Machining:

The major three electric discharge machining processes are:

1.    wire,
2.    ram, and
3.    small hole EDM,

All three methods are working under the concept of spark erosion technology. As the name specifies, material is removed from the workpiece by means of electrical discharges that generate sparks.

01- Principle of EDM process

Advantages of EDM:

1. In this process tool never applies any direct pressure on the work piece, hence highly delicate sections and weak materials can also be processed without any risk of their distortion.

2. Appreciably high value of Material Removal Rate (MRR) can be achieved as compared to other non-conventional machining processes.

3. Precise dimensional fine hole can be achieved with good surface finish.

4. Aspect ratio is maintained to the tolerance.

Disadvantages and Limitations of EDM Process:

1. Electrically non-conducting materials cannot be processed by EDM.

2. EDM process is not capable to produce sharp corners.

3. This process cannot be applied on very large sized work pieces. Because size of the work piece constrained with the size of the setup.

4. Intricate operation cannot be performed.

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