Page 59 - Fall 2023 EDM Today

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conductivity of the water in the clean tank of the
• Diffuser – Mounted under the head, the diffuser
distributes the incoming water stream over a wide area
dielectric system is monitored by the control system
which activates the pump which forces water from the
allowing it to percolate through the entire bed of the resin
clean tank through the deionizing container and returns
for maximum resin life. Without the diffuser, the water
it to the clean tank. The deionizing container contains
stream would likely make a channel in the resin bed,
deionizing resin (ion exchange resin is the formal
technical term) which removes the dissolved contam-
ination from the water. shortening its useful life.
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The deionizing container contains a mixture of two types
of resin beads. Cation resin beads to which positively
charged hydrogen ions are attached and anion resin
beads to which negatively charged hydroxide ions are
attached. Resin beads are porous, chemically inert
polystyrene beads that are chemically treated. These
beads (See Figure 1 and Figure 2) are small, highly
porous spheres. The porous structure provides a multi-
tude of sites for ions to become attached as a result of
chemical treatments.

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Figure 3

• Mixed Bed of Resin – A mixture of anion resin and
cation resin.
Figure 1
• Lance – The lance is basically a pipe which connects
to the head and reaches down through the resin bed to TECHTIPS
collect the treated water once it has passed through the
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resin.
• Strainer – Mounted to the bottom of the lance, the
strainer keeps the resin beads from exiting the tank
along with the treated water.

CO
CONDUCTIVITY/RESISTIVITYNDUCTIVITY/RESISTIVITY
Figure 2
THE RESIN CONTAINER RESIN CONTAINER
Although there are numerous options for the resin Depending upon the preference of the machine tool
THE
manufacturer, the electricity conducting properties of
deionized water are measured and reported by either of
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two parameters:
container, the vast majority of EDM dielectric systems
utilize fi berglass tanks.
Conductivity: µS/cm
•
The typical resin tank consists of the following
•
Resistivity: Ω
components (see Figure 3):
The resulting measurements of these parameters for the
same water sample are the reciprocal of each other as
• Shell – Usually made of fi berglass contains the mixed
bed of resin and all the system components.
•
• Head – Mounted to the shell via a large threaded
1 µS/cm = 1,000,000 Ω
connection and provides an attachment point for the shown in the following examples:
20 µS/cm = 50,000 Ω
•
lance, the diffuser, and the connections to the machine.
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EDM Today, Fall 2023 Issue