4. History of EDM
EDM came to be known generally since the study by Mr. & Mrs. Lazarenko of the Soviet Union in 1940's.
They found the new machining method when they were studying the phenomenon that switches were worn by the outbreak of sparks.
Commercialized EDM in Japan was put to practical use by Ikegai Ironworks and JAPAX circa 1953. However, different from current machines, EDM at that time was only available in "through-hole machining" because of large electrode wear.
"Bottomed machining" like current EDM became available since the power supply circuit with a transistor was put to practical use around 1968.
Later, "Sinker EDM" for "bottoming machining" by using shaped electrodes and "Wire EDM" for "contour machining" by using wire electrodes were distinguished.