Die-sink EDM abstract | EDM filters
Two Russian 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 RC circuit used to charge the electrodes.[3]
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. Initially constructing their machines from feeble 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 were able to produce 60 sparks per second. Later machines based on the Stark-Harding-Beaver design used vacuum tube circuits that were able to produce thousands of sparks per second, significantly increasing the speed of cutting
