Re: [Harp-L] What is Wire EDM?

[Robert Coble <robertpcoble@xxxxxxxxxxx>]

Rick asks:

"EDM? Whats' EDM? Electronic Dance Music....google google....ah! Electronic Discharge Material......? Yes? But what is that anyhow?"

Answer:
 
Electrical discharge machining (EDM), sometimes colloquially also referred to as spark machining, spark eroding, burning, 
die sinking, wire burning or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical 
discharges (sparks).[1] Material is removed from the workpiece by a series of rapidly recurring current discharges between 
two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the 
tool-electrode, or simply the "tool" or "electrode", while the other is called the workpiece-electrode, or "workpiece". 
The process depends upon the tool and workpiece not making actual contact.

When the voltage between the two electrodes is increased, the intensity of the electric field in the volume between the 
electrodes becomes greater than the strength of the dielectric (at least in some point(s)), which breaks, allowing current to 
flow between the two electrodes. This phenomenon is the same as the breakdown of a capacitor (condenser) (see also 
breakdown voltage). As a result, material is removed from both electrodes. Once the current stops (or is stopped, depending 
on the type of generator), new liquid dielectric is usually conveyed into the inter-electrode volume, enabling the solid particles 
(debris) to be carried away and the insulating properties of the dielectric to be restored. Adding new liquid dielectric in the 
inter-electrode volume is commonly referred to as "flushing". Also, after a current flow, the difference of potential between 
the electrodes is restored to what it was before the breakdown, so that a new liquid dielectric breakdown can occur.

Crazy Bob