The principles of EDM [2] are known since two centuries ago (in 1786, the British Physicist Priestley observed the presence of small craters in opposite electrodes in between a spark arised) focusing the first application for the principle: the preparation of colloidal dissolutions of metals.

The first application of the sparks to obtain geometrical shapes was made during the I and II World War. At the beginning, the possibilities of the technique were not considered due to the low productivity and lack of process control. In the first designs, the electrode and the part wear were similar and the presence of no desired arcs dropped the process performance. The gap between the electrode and the part was controlled by vibrating systems that reduced the electrode wear, which was still excessive.

The definitive push of the technology (initially in SEDM) was made in Moscu in 1943 by two married Societic Scientists: Dr. Boris and Dr. Natalya Lazarenko. They developed some key components that made possible to apply the technology in the industry: the spark generator (Resistance-Capacitance RC generator) and the first servo control circuit to keep a constant discharge gap. The new developments were presented in a job titled “About  the inversion of wear effect in electric discharges” [3] and published in April 23^rd, 1943 by B.N. Zolotych, a collaborator of the mentioned scientists and one of the most important researchers in the field of EDM.

The RC circuit (fig. 1) developed by Lazarenkos has been the base for the generators of commercial machines until recent years, being applied by some companies and newly introduced for micro EDM.

Figure 1. Scheme of the RC circuit  Developer by Lazarenkos

The first transistorised spark generators were Developer by 1964. Now they are applied in most commercial models.

The next big step for the EDM technology was made in 1969 by Prof. Bernd Schumacher with the development of the wire EDM machine.

Since then, the process improvements have consisted of better control electronics: numerical controls, spark generation, larger number of controlled axes, automatic threading systems, etc.

The improvements in the dimensional control and quality of the applied materials for the electrodes is also noticeable for both die sinking and wire EDM.

Since 70s, the WEDM process has increased its productivity 20 times, the process costs are now one third and the achievable surface roughness is 15 times better [4].

Figure 2. Market and research evolution in EDM [4]

The latest advances in the field of EDM are driven towards two clear tendencies: obtain a higher process productivity by increasing the spark power (while obtaining a higher reliability); reducing the spark energy to reduce the spark removal rate and produce smaller geometric shapes (microEDM).

Most of the EDM machinery producers are dedicating important resources to enhance the possibilities of their machines, analyse the process and develop new tools (electrodes, wires, guides, etc.) to cut with smaller electrodes and thinner wires.

In Japan, the developments by Prof. Kunieda and, speciall Prof. Masuzawa, have constituted some of the most important advances in the field of EDM and microEDM.

Prof. Masuzawa developed in 1985 the wire electro discharge grinding process (WEDG) that made possible to produce microelectrodes in the same SEDM machine with no run-out. Researchers applying this technique report the production of electrodes as small as Ø6mm to produce microholes. Prof. Kunieda has developed dry EDM techniques, process simulation techniques, etc..[5].

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