Page 71 - Fall 2023 EDM Today

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The U/V/Z-axes also need to be
greased once a year, and this is
accomplished using a manual
grease gun with the centrally
located grease fi ttings in the rear
of the machine for the U/V-axis,
and the front access panel on
the side of the Z-axis. There are
fi ve grease fi ttings per axis, and
these fi ttings supply grease to
each of the four linear guide trucks
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per axis and the main positioning
ball screw.

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Q: I am looking to replace my EDM dielectric fl uid in my machine, and I am considering switching to a newer
style full synthetic fl uid. What fl uid characteristics should I be aware of, and what are some of the differences
between the available synthetic fl uids today?

A: For starters, there are MANY good synthetic EDM dielectric fl uids available today. The two biggest benefi ts of
a synthetic fl uid are its longevity when compared to traditional petroleum-based fl uids, and synthetics provide far
greater health and safety for the operator (less skin irritation issues). Hands-down…synthetic is the way to go!
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As for what dielectric fl uid attributes to look for, this will depend on what type of work you perform. Historically,
petroleum-based fl uids tend to be thicker and have a higher viscosity value than most synthetic fl uids, and these
characteristics were good, considering the large surface area electrode size and high amperage burns that were
commonplace in the past when these fl uids were initially developed.
For example, a thicker fl uid is ideal if you intend to machine larger surface areas (4” square/100mm square or larg-
er) with maximum power levels (100 amps), as the thicker fl uid will hold up better against the big burns. A thinner
fl uid will perform better on smaller surface areas and deeper geometry features, as the thinner and more “free fl ow-
ing” fl uid enhances the fl ushing characteristics and helps move the smaller debris more effi ciently.

With the advancement of high speed hard milling capabilities, modern Sinker EDM applications have shifted to-
wards favoring smaller and deeper geometry features that cannot be milled effi ciently, such has a support rib
feature found in plastic injection mold tooling. Sinker EDM machines have also advanced in recent years and now
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achieve signifi cantly faster Z-axis jump and acceleration speeds, making a thinner EDM fl uid more effi cient for the
smaller and lighter-duty EDM’ing found today.
On a side note, today’s Sinker EDM high speed Z-axis jump motions have helped improve cycle time while allowing
greater effi ciency of unattended machining. Gone are the days of having to “babysit” a machine and continuously
adjust and re-aim external fl ush nozzles for best effi ciency. With today’s newer high speed jump technology, Sinker
EDM machines utilize the jump motions to facilitate hydraulic fl ushing of the debris…these modern jump motions
essentially transform the electrode into a pump that helps push and pull the debris from the spark gap.

To establish some EDM dielectric fl uid viscosity values to consider, a “thicker” fl uid will have a Kinematic Viscosity
at 40°C of 3.0 cST or higher or a 32 SUS* at 100°F, whereas a “thinner” fl uid will be around a Kinematic Viscosity at
40°C of 2.5 cSt or a 12 SUS* at 100°F. (Continued on next page)
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EDM Today, Fall 2023 Issue