Electrode Discharge Machining(EDM)

Mechanism of material removal-

Spark & Erosion
Melting & Vapourisation

Application

Machining of die

EDM is a high voltage low current process and in order to develop a High Voltage electrical energy capacitor bank is used during the major portion of cycle time capacitor Bank charging and for a very small period of time, it will charges to produce a very high intensity of Park between tool and workpiece.
Initially, the tool water that is filled with dielectric fluid (kerosene is used as a dielectric fluid) which is initially nonconducting in nature and when a required voltage is applied it turns to be a conducting in nature in a very narrow region.
The park will be bombarded over the work-piece. The intensity of spark is so high that a small amount of work-piece material melted out as well as vapourises. therefore, the mechanism of material removal is melting & vapourization.
When a spark is bombarded over the workpiece the temperature rise over the workpiece will take place because of the impact of a spark sharp corner present over the tool will be damaged this is known as thermal damage over the tool and due to thermal damage, sharp corner on the workpiece can't be produced.
Due to continuous material removal debris will be accumulated between the tool and workpiece which will decrease the material removal rate. To filter out the debris dialectic fluid is continuously circulated with the help of a centrifugal pump, It also controls the temperature of dielectric fluid. Graphite is used as a tool for two reasons
It is a good conductor of electricity
It had a very high melting point
Since the thermal conductivity of graphite is poor therefore to improve the thermal conductivity, Copper is also added to graph graphite.

Electrode Discharge Machining(EDM)