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TECHTIPS • FALL 2023

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EDM WATER DIELECTRIC DEIONIZING
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SYSTEM CONSIDERATIONS

BY ROGER KERN
PRINCIPAL CONSULTANT | INTERNATIONAL TECHNOLOGY PROFESSIONALS

While water dielectric is most commonly associated with Wire EDM, water is also utilized in the majority of Fast Hole
EDM applications as well as a small number of Sinker EDM applications. This article will focus on the practical
application of ion exchange resins in EDM. [Editor’s note: For a complete dissertation on the subject of water dielectric
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systems and ion exchange regeneration, please see the article in the Summer, 2010 issue available online at
edmtodaymagazine.com by clicking on the Archives tab and then clicking on Linked Features.]

The electrical discharge process contaminates the

THE BASICS BASICS
THE
water in two ways. The most obvious contamination
produced by a discharge is the re-solidifi ed wire and
The role of the dielectric in serving as the medium for
workpiece material that is the product of the discharge
discharges is our primary concern in this article. The
dielectric serves a dual role as both an insulator and a
removed by the fi lter subsystem of the dielectric sys-
conductor. Prior to the discharge, the deionized water
tem. A less obvious, but very signifi cant, contamination
acts as an insulator, allowing the electrical potential – the solid contaminant. The solid contaminant is
produced by a discharge is the dissolved contaminant.
between the wire and the workpiece to build without
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The dissolved contaminant consists of metal salts pro-
it bleeding off through the fl uid. Once the electrical
duced during the discharge that dissolve into the water
potential between the wire and the workpiece builds to
just as table salt dissolves into water. These dissolved
a certain intensity, the dielectric breaks down and forms
salts increase the conductivity of the water, causing
an electrically conductive path (known in EDM as the
spark energy to bleed off prior to the actual occurrence
Discharge Channel). This conductive path allows the
of the discharge, adversely affecting the consisten-
energy of the spark to be transferred from the wire to the
cy and effi ciency of the discharge. Since these salts
workpiece for metal removal. The role of the Discharge
are dissolved in the water, they cannot be fi ltered out
Channel is crucial in assuring that each discharge is
the same, affecting cutting speed, surface fi nish, and
removed by the deionizing subsystem of the dielectric
overburn. Thus, maintaining a constant condition of
system. The deionizing subsystem consists of a pump,
the deionized water dielectric is essential to obtaining mechanically by a fi lter. The dissolved contamination is
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control system, and a deionizing container. The level of
consistent results from the EDM process.
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