Page 9 - Summer 2024
P. 9

EDM Today Magazine                           EDM Today Magazine                            EDM Today Magazine



             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
   EDM Today Magazine                           EDM Today Magazine                            EDM Today Magazine
                                                              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
   EDM Today Magazine                           EDM Today Magazine                            EDM Today Magazine
                                                              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.
   EDM Today Magazine                           EDM Today Magazine                            EDM Today Magazine
                                                              International Technology Professionals
                                                              www. itp4edm.com
             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?
   EDM Today Magazine                           EDM Today Magazine                            EDM Today Magazine
             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
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