Wire EDM Machine Operation Chapter 1
Copyright November, 98 Page 1-1 Sodick Inc.
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The first key concept that you must understand is the basic principle of the EDM process.
One good analogy of what occurs in the EDM process is what is constantly happening in
your automobile engine. The spark plug that ignites the fuel in the combustion chamber is
constantly receiving a great amount of voltage and current to form a spark. As time goes
on, and the spark plug wears, you will notice a certain amount of pitting on the electrodes
of a worn spark plug. This pitting is caused by exactly the same elements that work in the
EDM process. The heat generated by the spark causes a small amount of the electrode to
melt, and as time goes on the melted material is blown away from the electrode of the
spark plug. Of course, the spark plug is designed to fight against this pitting, but in the
EDM process the melting of material and the flushing away of the melted particles is
desirable, and the machine is designed accordingly.
In simplified terms, this is what happens during the wire EDM process. The wire passing
through the machine has an intermittent voltage applied to it. As the wire comes close to
the material (but not actually touching it), an ionization channel forms and amperage
flows through this channel vaporizing a tiny area of the workpiece. This channel or gap
must be filled with a dielectric fluid, in this case deionized water that acts as a flushing
medium to remove the vaporized particles, an insulator and a cooling medium. The
electricity going to the wire is then turned off and the vaporized material will
instantaneously solidify to form a small particle. The flushing will then remove the
particle from the gap and the process starts over again. This process repeats thousands of
times per second. It is this constant process that eventually machines the workpiece to
your specifications.
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WIRE DIAMETER AND WIRE GUIDES
The first consideration the operator should give thought to is the diameter of the wire
used to machine the part with. Generally speaking, the larger the diameter, the faster the
machining can occur. If the maximum inside radius specified on the print was .005" you
would have to use .008"or smaller diameter wire. When you take the (over-burn) the arc
distance between the wire and the workpiece plus the radius of the wire, this value will be
the radius you will get in the corner.
Sodick allows the following wire diameters and wire guides sizes, on most machines.
.004 Diameter Wire (.11mm or .12mm wire guide)
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