Page 75 - Fall 2023 EDM Today

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Roger Kern’s reply:
removal rate, but a side effect of this power is a re-plat-
ing of the base material back onto the electrode. In
There are two reasons for draining a resin tank prior to
this case, I believe it is the components of the tungsten
returning it for regeneration:
carbide workpiece material that are plating itself on the
outer surface electrode, making machining much more
of the water in the tank is substantial.
diffi cult than the virgin copper tungsten material. • To minimize your shipping charges, as the weight
To avoid the water freezing, expanding and
•
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There is not much that can be done to prevent this
bursting the tank if its return path to your supplier
from occurring other than to EDM machine with lower
includes transiting an area where the temperature
power levels, which will result in longer cycle time and
drops below freezing.
higher electrode wear. I’m not sure of the extent of
issues this is causing with the electrode re-machining
The best way to purge the water from the tank is to
process, but maybe you can just eliminate the used
apply low pressure compressed air to the inlet fi tting
1st rough cut electrode from the re-machining plan.
on the tank head. Connect a piece of hose to the tank
I know that copper tungsten material is expensive, but
outlet and route it into a bucket. Then apply the
perhaps you can set these roughing electrodes aside
until you have a full batch that can then be machined
Caution: Depending upon the tank design and construc-
with a different re-machining program/process. pressure until only air comes out of the drain hose.
tion, there is a possibility of catastrophically bursting
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the tank if too much pressure is applied, possibly
Roger Kern’s further reply:
causing serious injury. When I owned a consumables
Brian is absolutely correct! International Technology
company, I sold a tank draining kit that included a
Professionals, in conjunction with the University of
pressure relief valve inserted into the inlet line set at
Connecticut, has conducted Scanning Electron
20 psi to avoid that possible hazard. If you construct
Microscope EDX investigations on the surfaces of
your own tank draining system, you should either
used electrodes. These investigations have revealed
include a pressure regulator in its supply line or add
that, in addition to deposits of pyrolytic graphite
a pressure relief valve to the supply line.
derived from the oil dielectric, there is a transfer of a
One further important note: Depending upon the
certain amount of workpiece material to the electrode.
applicable EPA or your state and municipal regulations,
One possible course of action would be to increase
the water drained from your resin tank may be consid-
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the depth of cut in the milling process to possibly
ered hazardous waste. Therefore, do not dispose of
get “under” the surface layer into the virgin copper
it into a drain or out on the ground. The safest way to
tungsten material, which might facilitate the
dispose of the water drained from a resin tank is to pour
machining process.
it back into your machine’s dirty tank.
Finally, before consigning your tank to the carrier, be
Resin Tank Drain Water Disposal
certain that both the inlet and outlet ports are plugged
My consumables supplier has informed me that I
the tank contaminating the shipping carton and possi-
need to drain the water from my exhausted resin
bly the carrier’s truck.
tanks prior to shipping them for regeneration. to avoid any possible seepage of residual water from
Why do I need to do this and how should I do this?
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- Kevin
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EDM Today, Fall 2023 Issue