Editing Electrical discharge machining (section)

==History==
The erosive effect of electrical discharges was first noted in 1770 by English physicist [[Joseph Priestley]].

===Die-sink EDM===
Two Soviet scientists, B. R. Lazarenko and N. I. Lazarenko, were tasked in 1943 to investigate ways of preventing the erosion of tungsten electrical contacts due to sparking. They failed in this task but found that the erosion was more precisely controlled if the electrodes were immersed in a dielectric fluid. This led them to invent an EDM machine used for working difficult-to-machine materials such as tungsten. The Lazarenkos' machine is known as an R-C-type machine, after the resistor–capacitor circuit ([[RC circuit]]) used to charge the electrodes.{{sfn|Jameson|2001|p=8}}<ref>{{cite journal |last=Lazarenko, B.R.; Mikhailov, V.V.; Gitlevich, A.E.; Verkhoturov, A.D.; Anfimov, I.S. |title=Distribution of elements in surface layers during electric spark alloying. (Raspredelenie Elementov V Poverkhnostnykh Sloyakh Pri Elektroiskrovom Legirovanii) |journal=Surf. Eng. Appl. Electrochem. (Elektronnaya Obrabotka Materialov) |volume=1977, 3 |pages=28–33}}</ref><ref>{{cite journal |last=Lazarenko, B.R.; Duradzhi, V.N.; Bryantsev, I.V. |title=Effect of Incorporating an additional inductance on the characteristics of anode and cathode processes. (O Vliyanii Vklyucheniya Dopolnitel'noi Induktivnosti Na Kharakteristiki Anodnogo I Katodnogo Protsessov) |journal=Surf. Eng. Appl. Electrochem. (Elektronnaya Obrabotka Materialov) |volume=1979, 5 |pages=8–13}}</ref><ref>{{cite journal |last=Lazarenko, B.R.; Lazarenko, N.I. |title=Electric spark machining of metals in water and electrolytes. (Elektroiskrovaya Obrabotka Metallov V Vode I Elektrolitakh) |journal=Surf. Eng. Appl. Electrochem. (Elektronnaya Obrabotka Materialov) |volume=1980, 1 |pages=5–8}}</ref>

Simultaneously but independently, an American team, Harold Stark, Victor Harding, and Jack Beaver, developed an EDM machine for removing broken drills and taps from aluminium castings.<ref>{{cite book |last1=Krar |first1=Stephen F. |last2=Gill |first2=Arthur R. |title=Exploring advanced manufacturing technologies |date=2003 |publisher=Industrial Press |isbn=0831131500 |page=6.2.1 |edition=1st |url=https://books.google.com/books?id=TGkfsC77pdwC&pg=SA6-PA10-IA1}}</ref> Initially constructing their machines from under-powered electric-etching tools, they were not very successful. But more powerful sparking units, combined with automatic spark repetition and fluid replacement with an electromagnetic [[interrupter]] arrangement produced practical machines. Stark, Harding, and Beaver's machines produced 60 sparks per second. Later machines based on their design used [[vacuum tube]] circuits that produced thousands of sparks per second, significantly increasing the speed of cutting.{{sfn|Jameson|2001|pp=10–12}}
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===Wire-cut EDM===

The wire-cut type of machine arose in the 1960s for making tools ([[die (manufacturing)|dies]]) from hardened steel. The tool electrode in wire EDM is simply a wire. To avoid the erosion of the wire causing it to break, the wire is wound between two spools so that the active part of the wire is constantly changing. The earliest [[numerical control]]led (NC) machines were conversions of punched-tape vertical milling machines. The first commercially available NC machine built as a wire-cut EDM machine was manufactured in the USSR in 1967. Machines that could optically follow lines on a master drawing were developed by [[David H. Dulebohn]]'s group in the 1960s at Andrew Engineering Company<ref>Dulebohn, "Tracer controlled machining by electrically induced erosion", {{US patent|3614372}}, filed 4 December 1969, issued 19 October 1971.</ref> for milling and grinding machines. Master drawings were later produced by computer numerical controlled (CNC) plotters for greater accuracy. A wire-cut EDM machine using the CNC drawing plotter and optical line follower techniques was produced in 1974. Dulebohn later used the same plotter CNC program to directly control the EDM machine, and the first CNC EDM machine was produced in 1976.{{sfn|Jameson|2001|pp=12–17}}

Commercial wire EDM capability and use has advanced substantially during recent decades.<ref name="Rogers_2018">{{citation |last=Rogers |first=Barry |year=2018 |title=The Remarkable Abilities of Wire EDM |journal=TechSpex |url=https://www.techspex.com/knowledgecenter/guide-to-buying-machine-tools/buying-a-wire-edm |access-date=2018-05-21 |postscript=. |archive-date=2018-05-22 |archive-url=https://web.archive.org/web/20180522112039/https://www.techspex.com/knowledgecenter/guide-to-buying-machine-tools/buying-a-wire-edm |url-status=dead }}</ref> [[Feed rate]]s have increased<ref name="Rogers_2018"/> and [[surface finish]] can be finely controlled.<ref name="Rogers_2018"/>