How It Works
There are a series of non-stationary, timed electrical pulses to remove material from a workpiece during the EDM process. The electrode and the workpiece are held by the machine tool, containing the dielectric.
A power supply controls the timing and intensity of the electrical charges and the movement of the electrode about the workpiece.A discharge is initiated at the spot where the electric field is most vital.
Under the effect of this field, electrons and positive free ions are accelerated to high velocities and rapidly form an ionized channel that conducts electricity.
At this stage, the current can flow, and the spark forms between the electrode and workpiece, causing many collisions between the particles. During this process, a gas bubble develops, and its pressure rises very steadily until a plasma zone is formed.
The plasma zone quickly reaches very high temperatures, in the region of 8,000 to 12,000′ Centigrade, due to the effect of the ever-increasing number of collisions, which causes instantaneous local melting of a certain amount of the material at the surface of the two conductors.
When the current is cut off, the sudden reduction in temperature causes the bubble to implode, which projects the melted material away from the workpiece, leaving a tiny crater.
The eroded material then resolidifies in the dielectric in small spheres and is removed by the dielectric. All this without the electrode ever touching the workpiece.
Making EDM a no-contact machining process allows you to achieve tighter tolerances and better finishes in a wide range of materials that are otherwise difficult or impossible to machine with traditional processes.