ELECTRICITY DISCHARGE MACHINE-EMD.

ELECTRICITY DISCHARGE MACHINE(EDM) PROCESS AND HOW IT WORKS?                                                        Electrical Discharge Machining (EDM) is a non-traditional machining and electrothermal process; in which material from the workpiece is removed by using electrical discharges (sparks).
It was first observed in 1770 by Joseph Priestley. He was an English physicist.

working Of Electric Discharge Machining

In the EDM voltage pulse machine, the material is removed by rapidly recurring (repeating) discharges of current in between the electrodes. The electrodes are separated by a dielectric liquid and a high voltage is applied across it.
It is used to machine those materials which are difficult to machine and have high strength temperature resistance.
EDM can be used to machine only electrically conductive materials. Otherwise, it cannot be used.
One of the electrodes is called a tool and the other is called the workpiece. Here the tool is connected with the negative terminal of the power supply and the workpiece is connected with the positive terminal.

WORKING PRINCIPLE
In Electrical discharge machining; a potential difference is applied across the tool and w/p in pulse form. The tool and workpiece must be electrically conductive and a small gap is maintained in between them. The tool and workpiece are immersed in a dielectric medium (kerosene or deionized water). As the potential difference is applied, electrons from the tool start to move towards the workpiece. Here the tool is negative and w/p is positive.

The electrons moving from the tool to the w/p collide with the molecules of the dielectric medium. Due to the collision of electrons with the molecule, it gets converted into ions. This increases the concentration of electrons and ions in the gap between the tool and w/p. The electron moves towards the w/p and ions towards the tool. An electric current is set up in between the tool and w/p and called as plasma.

As the electrons and ions strike the w/p and tool, its kinetic energy changes to heat energy. The temperature of the heat produced is about 10000 degrees Celsius. This heat vaporizes and melts the material from the workpiece. As voltage breaks down, the current stops to flow between the tool and w/p. And the molten material in the w/p is flushed by circulating dielectric medium leaving behind a crater. The spark generation is not continuous because the constant voltage is not applied across the electrodes. The voltage is applied in pulse form.

TYPES OF ELECTRICAL DISCHARGE MACHINE

There are two types of EDM machines…

1-Ram/Sinker EDM;-
This EDM machine consists of a tool and workpiece immersed in a dielectric medium. It consists of a ram-type tool and it may be created according to the shape or form required to produce on the workpiece. It is also called as cavity-type or volume EDM.

2- Wire EDM;-
In wire EDM, a thin single-strand wire is used to cut the material from the workpiece. The wire is usually made of brass. A constant gap is always maintained between the wire and w/p. The wire is continuously fed through the workpiece submerged in a tank with a dielectric medium. Here spark is generated in the gap between the wire and workpiece. It is used to cut metal as thick as 300 mm and to make punches, dies, and tools from hard metals that are difficult to cut from other methods.

WORKING OF EDM

1-In EDM, first, the tool and w/p are clamped to the machine. After that with the help of a servomechanism, a small gap (of a human hair) is maintained in between the tool and workpiece.
2-The tool and workpiece are immersed in dielectric medium (kerosene of deionized water).
3-A potential difference is applied across the Electrode. An electric spark is generated between the tool and the workpiece. This spark generates a heat of about 10000 degrees Celsius. And due to this heat, the material from the workpiece starts to vaporize and melts.
4-The spark generation in electrical discharge machining is not continuous. As the voltage breaks, the dielectric fluid flushes away the molten materials leaving behind a crater.
5-This process keeps continuing and machined the workpiece.

ADVANTAGES OF EDM MACHINE

1 This process keeps continuing and machined the workpiece.
2 This process keeps continuing and machined the workpiece.
3 It can machine complex shapes that are not manufactured by conventional machine tools.
4 It can produce tapered holes.

DISADVANTAGES OF EDM MACHINE

1-It can machine only electrically conductive materials.
2-Low rate of metal removal.
3-Takes extra cost and time for preparing electrodes for Ram/Sinker EDM.
4-High power consumption.

CONCLUSION;-
Project Electricity Discharge Machining has a huge market in the present scenario.
The EDM is widely used in sheet metal operation worldwide.
Hence; the learning and experience of the industry were worthwhile.

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