Page 52 - EDM Today Winter 2025

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The key implication of this formula is that the gap size
Pulsed ECM
Given that the process’s copy precision relies on the
(which determines the machine’s copy precision) is
inversely proportional to the relative speed between
relative speed of the electrodes, a major advancement
the tool electrode and the workpiece, measured along
introduced about 30 years ago was the vibration of the
the advance vector (typically vertical). Since the lateral
tool electrode at 50 or 100 Hz. In this variant, the ECM
relative speed is nearly zero, the side gap becomes larger pulse is synchronized with the lowest position of the Z
than the frontal gap. Mathematical models give the side
electrode is typically 10 to 200 um.
gap as a function of the contour’s angle inclination (cosφ
method, [11]). The steeper the shape, the larger the
A schematic diagram of a typical machine head is
gap, and sharp corners tend to round off. Therefore, the axis, as shown in Fig. 4. The travel of the vibrating
provided in Fig. 5.
optimal shape of the tool electrode must be determined
Fig. 3: The dimensionality problem of ECMEDM Today Magazine
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through extensive preliminary testing.

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Typical values of vsp are listed in Table 1:

Fig. 4: Pulsed ECM principle [3]

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Fig. 5: Schematic diagram of a typical machine vibrating head [3]
This method allows the gap to be reduced to just a few
microns, achieving process accuracy better than 5 µm.
Table 1: Typical values of vsp [mm3/min.A]
Fig. 6 shows a pulsed ECM machine, which includes the
mechanical components, generator, CNC, and electrolyte
treatment unit. ECM machines must be corrosion resis-
tant, and they are typically constructed from materials
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such as stainless steel, granite, and specialized plastics.

Table 2: Key fi gures of ECM Fig. 6: A pulsed ECM machine [8]
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