The History of Electroerosion Processing

The British scientists J. Priestley described the metal erosion phenomenon under the action of electric current at the end of the 18th century. It was observed that a spark or longer arc will occur at the point of rupture when an electrical circuit is broken. In addition, a spark or arc has a powerful damaging effect on the broken circuit contacts, named erosion. Electrical erosion is the subject of contacts of relays, switches, and other similar devices. Much research has been done to eliminate or at least reduce the destruction of such contacts. 

1943 is deemed to be the date of birth of the electroerosive processing of materials, from which B.R. and N.I. Lazarenko prioritize the invention. The scientists discovered that the liquid became cloudy after the first discharges between the contacts by putting the electrodes in a liquid dielectric constant and opening the electrical circuit. 

They found this to be because tiny metal balls show up in the liquid resulting from electrode electrical erosion. Scientists decided to increase the destruction effect and attempted to use electrical discharges for uniform metal removal. To this end, they placed the electrodes (the tool and the workpiece) in a dielectric liquid that cooled the particles of molten metal and prevented them from settling on the opposite electrode.

The pulse generator was used as a condenser bank charged from a constant current source; the charging time of the condensers was regulated by a rheostat. Thus there was the first installation in the world of electrical erosion. Moving the electrode tool to the workpiece. The field strength of the inter-electrode gap (MEP) increases as they approach. 

Of particular importance was the invention of electroerosive processing (EEO). A completely new method was added to the traditional shaping methods (cutting, casting, forming) in which electrical processes were used directly. Initially, only spark discharges generated by a condenser in the so-called RC generator were used to process EDM. Therefore, at that time the new process was called the treatment of electric spark. 

In 1948, M.M. Pisarevsky enacted electrical pulse treatment predicated on the use of arc discharge pulses. In the early 50s, this technique began to be adopted in the industry. Evolution continued dynamically in the following years: 1967 — development of poorly wearing tool electrodes, 1975 — introduction of CNC systems and adaptive control, 1979 — use of planetary heads and obtaining mirror surfaces, 1987— ultra-low wear of tools. Machining parts error on any EDM Manufacturing Services machines fell from ± 30 to ± 5 microns, and machines’ annual output increased 8-10 times.

When a certain field strength was reached at the site at a minimum distance between the electrode surfaces, measured perpendicular to the treated surface and referred to as the minimum electrode gap, an electrical discharge arose as a result of which the workpiece area was destroyed. Processing products entered the dielectric liquid, where they were cooled, failed to reach the electrode tool, and then deposited at the bottom. The electrode tool pierced the plate after a while, and the contour of the hole exactly matched the profile of the tool. Thus, for the dimensional processing of materials, the phenomenon considered harmful was applied. The history of the development of the EDM processing method of materials isn’t just a vivid reflection of the domination of the world’s technological space by high-tech technologies, but also underlines the importance of owning and further developing such technologies.

 

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