Page 9 - Summer 2024
P. 9
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Regarding your second issue: Wire detection issues -
Recently, two possible solutions have arisen:
many machines utilize optical sensors to detect the
• Copper wire
presence of the wire along various positions of the
• Nickel coated wire
wire path as it travels through the upper head. It is
possible that these optical sensors are not responding
Both have signifi cant issues as noted below:
to the dark color of the wire. That could be an issue
with an individual sensor being weak or possibly that
the machine electronics is not designed to detect a
with DC power supplies there is severe copper plating
dark color wire, in which case a factory fi x involving the Copper wire cuts quite slowly, and on older machines
in the wire path slot that will actually close the slot
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behind the wire and bind it to the workpiece. I have
calibration of the machine electronics/software would
found that this plating condition occurs even with
be necessary.
state-of-the-art anti-electrolysis power supplies, but
not to the extent that it stops the cut. The resulting
surface will have some copper plating that can be
Oversize Wire Causing Threading Issues
removed by subsequent skim cuts, but even then there
I am having issues with my wire unable to pass
might be some small amount of copper contamination
in some areas.
through the guide opening. I think the wire is oversize.
- Steve
a brass core or a brass core coated with a beta
Roger Kern’s reply:
or gamma brass alloy. During the rough cut, as the
nickel coating is consumed, the underlying zinc will
I have examined the wire sample that you sent to me. Nickel coated wires have a thin layer of nickel covering
still contaminate the workpiece surface. Subsequent
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skim cuts that do not penetrate the nickel coating will
The standard tolerance for EDM wire diameter is +0/-2
remove the contaminated workpiece surface. So, this
microns (+0-.00008”).
type of wire does offer a solution to the contamination,
Your wire measured approximately .1 micron oversize
but is very costly and requires the addition of skim
(.000004” or four millionths oversize) on my laser
cut(s) time to the operation sequence.
micrometer, a miniscule amount which is within the
measuring uncertainty of our laser micrometer.
Thus, there are no simple solutions to your issue at
this time, although there is ongoing research in hopes
It is likely that the method you use to prepare the end
of developing a high performance wire that has no
of the wire for threading is causing this issue.
Please see the Tech Tips article in this issue for a
complete discussion of this matter, along with copper or zinc in its composition.
Roger Kern | Principal Consultant
suggested solutions.
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Workpiece EDM Surface Zinc Contamination Issues
I am being asked to Wire EDM an aerospace com-
ponent that is not allowed to have any zinc contam-
ination on the EDM’d surfaces. What wire would you
suggest for this application?
- Anthony
Roger Kern’s reply: Need an answer right away?
Got an EDM question?
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Virtually all of the commonly used wires have zinc in
either their core or coatings. During the EDM process,
some of the zinc from the wire becomes a part of the
Get an answer in 24 hours!
workpiece EDM surface. Up until recently, the only
viable solution has been to use molybdenum wire.
However, moly wire has signifi cant disadvantages
such as:
Simply visit our website and choose
“Ask EDM” from the ”Resources” tab
• High cost
• Low cutting speed
• High lower power feed contact wear
• Straightness issues
• Shelf life issues www.EDMtodayMagazine.com
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EDM Today, Summer 2024 Issue