Editing Electrical discharge machining (section)

===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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