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THE PERILS OF MULTI-ELECTRODE BURNS
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recent consulting engagement with a client attempting to
When Sinker EDM is used in production applications, pro-
produce six parts at a time and struggling with EDM’ed
cess engineers often consider the possibility of utilizing
multiple, simultaneous burns to boost production without features that exceeded feature tolerances. This article
having to purchase multiple machine tools. Despite the
will attempt to identify the numerous possible sources of
fact that multiple, simultaneous burns will mean propor-
unacceptable variations with EDM’ed surfaces from this
type of process.
tionately longer burn times, since EDM is a one spark at
a time process and because EDM is also an unattended
process, this pattern of thought makes sense. [Editor’s
processing is to assure that each individual electrode
note: While multi-lead power supplies (often advocat- The key to success for multiple electrode/workpiece
is positioned correctly with respect to each individual
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ed by this author) will address the increased burn time
workpiece’s datums. As will become evident, that is not
issue, they have not been embraced by the industry.]
such a simple matter.
Unfortunately, process engineers often fail to appreciate
Let’s look at a typical example in which we are burning a
the ramifi cations of error accumulation associated with
single feature simultaneously in six workpieces. In many
multiple electrode/multiple workpiece processing that
cases, such a setup would consist of:
can adversely affect the quality of workpieces produced
•
by this process.
A workpiece baseplate fastened to the machine table
The permutations and combinations of tolerance
accumulation that can result from multiple electrode/
An electrode baseplate fastened to the machine ram
•
multiple workpiece processing often produce unaccept- • Six individual workpiece locating fi xtures
•
Six individual electrode holders
able, inconsistent variation in the workpieces produced
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by this process. I encountered this situation during a
Six electrodes
•
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