Harper and Simmons

Wire Erosion Guidelines

Back to wire erosion

  • Wire eroders cut fastest through solid blocks of conducting material.
  • Hardened tool steel cuts as easily as soft tool steel (see stress relieving)
  • When planning tools, it should be the first process on a block of material where possible, with the exception of blanking tools, where drilling of retaining holes and wire start holes should be done first, then the blocks hardened.
  • To get the fastest speed from a machine, the top and bottom of the workpiece should be ground flat, with no cavities, tapped holes, or machined forms present on the cutting path, as the heads of the machine should be within 0.2mm of the workpiece at all times.
  • Although the latest machines have very good generators, consideration should be made (particularly in aerospace and safety critical applications) to skim cutting the work to reduce the recast layer. Skim cutting is effectively a finishing pass, which also improves accuracy where necessary.
  • Accuracy – As a rule of thumb, 1 cut through 100mm thick will be accurate to about 20µ microns (0.001"), 200mm about 30µ microns, 300mm about 40µ microns, 400mm about 60µ microns, 500mm about 100µ microns. This assumes good workpiece preparation.
  • Stress relieving is absolutely vital, as residual stress in the block causes continual wire breakage, distortion after cutting, and deviations from the path as the variation in spark intensity dislocates the wire within the slot. Tool steel should have at least 2 tempers, larger sections 3 tempers.
  • SG Iron cuts very slowly – in some cases not at all. Materials that have inclusions, or that have a high non conductive content such as sulphur are slow to cut, whereas pure materials cut relatively quickly, with less operator intervention for wire breaks and feed holds.

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