ARCHIVE 06The Lineage of EDM Machines

The Discovery of EDM and the Start of Research in Japan (1943–1952)

Damage to metal by electric discharges had been known since the 18th century, but the accepted view is that today's EDM began in 1943, when the Soviet physicists Boris and Natalya Lazarenko proposed using it for machining in a paper and filed a patent. Their research on keeping electrical contacts from wearing away by sparking gave them the idea of doing the opposite: using that wear to remove metal^[2]. The 1955 technical book Seimitsu shiage-ho (Precision finishing methods) reports that the couple received the Stalin Prize for this work in 1946, and that Britain had been offering commercial machines since around 1952^[1].

Word had reached Japan during the war as well. According to the same book, around 1942 naval aviation intelligence reported that "in America they drill and cut with sparks or arcs", and according to Inoue Kiyoshi, who later founded an EDM company, Mitsubishi Heavy Industries' Mizushima Works also experimented, but got no further than something like fusion cutting^[1].

Otori Seizaburo of the University of Tokyo and "electrical discharge machining"

After the war, in 1947, news of the couple's research reached Professor Otori Seizaburo of the University of Tokyo through newsreels and literature. Having studied how electrodes wear in arc discharges, he grasped the principle at once, began research in 1948 and had experimental equipment ready the following year. It was also Professor Otori who named the process "hoden kako-ho" (electrical discharge machining). In the 1950s universities such as Tohoku, Chiba and Niigata, research institutes such as the Railway Technical Research Institute, and company laboratories joined one after another, and in 1955 the Electrical Machining Research Group was formed, which led to the Japan Society of Electrical Machining Engineers (1967)^[2].

The First Japanese Machines and the Birth of the Makers (1953–1964)

In 1953 Nihon Hoden Kako Kenkyusho (Japan EDM Research Institute) was founded as an affiliate of the long-established machine tool maker Ikegai Iron Works. Its founder, Inoue Kiyoshi, was an engineer who had researched EDM at Mitsubishi Heavy Industries, and he set up the company after hitting it off with Okazaki Kaheita, then president of Ikegai Iron Works^[2].

1954: Japaxtron D3

In March of the following year, 1954, the company completed Japan's first practical EDM, "Japaxtron D3", and delivered it to the Tokyo Institute of Technology. It was an original design, unlike Western machines, and was also called a spark-discharge hole-piercing machine. It is now at the Nippon Institute of Technology Museum of Industrial Technology, and in 2024 it was registered as Essential Historical Materials for Science and Technology (No. 373)^[3][4]. Hoden kako (Electrical discharge machining) by Otori Seizaburo and Kurafuji Hisao, published the same year, 1954 (the first academic book on the subject in Japan), introduces four Japanese makers: Nihon Hoden Kako Kenkyusho, Koike Sanso Kogyo, Asahi Pump Hatsudoki Seisakusho and Osawa Seisakusho. Koike Sanso's business, however, ended after a little more than ten years, and the other two were very short-lived^[2].

Mitsubishi and Seibu Denki Kogyo enter the field

In 1958 Mitsubishi Shipbuilding and Mitsubishi Electric teamed up to start producing the DM-101 EDM, with Mitsubishi Shipbuilding (Hiroshima) handling the machine and Mitsubishi Electric the electrical parts such as the power supply^[2]. The small DM-50B of 1963 stabilized machining with a power supply using a high-frequency superimposed circuit that keeps discharges from concentrating in one spot^[5]. In 1964 the business was consolidated into Mitsubishi Electric and production moved to its Nagoya Works^[2]. In October 1962, Fukuoka-based Seibu Denki Kogyo (today's Seibu Electric & Machinery) developed a die-sinking EDM with the help of Yaskawa Electric, which had been researching EDM since around 1953, and exhibited the Type E-304 at a trade fair^[2][7].

EDMs were still rare machines then. The 1963 book Sekai no kosaku kikai kogyo (The world's machine tool industry) reports that a 1958 US survey of machine tool equipment counted 578 EDMs, a tiny fraction of the total^[6]. Even so, they began to spread in Japan: the 1963 book Kanagata kosaku gijutsu (Die and mold making technology) lists ten makers, including Ikegai/Japax, Mitsubishi Shipbuilding/Electric, Koike Sanso, Seibu Denki, Hitachi Zosen and Makino Furaisu, says well over a thousand machines were in operation, and names Japax's Type D-104H as a representative machine^[9]. Nihon Hoden Kako Kenkyusho had been renamed Japax in 1960^[3], and the 1963 Kokusan kosaku kikai sogo katarogu (Comprehensive catalog of Japanese machine tools) lists four Ikegai Tekko models, including the Type D104H "automatic precision EDM die-sinker", alongside Mitsubishi Shipbuilding's "Mitsubishi Diax EDMs", Types DM-50 and DM-102^[8].

Die-Sinking EDMs Spread to Die Making (1965–1971)

Early EDM work centered on piercing "through holes" in hardened steel. Because the electrode itself also wears away, it was unsuited to complex blind shapes (cavities in dies and molds). In the late 1960s, semiconductor power supplies appeared and greatly reduced electrode wear, making EDMs usable for three-dimensional blind cavities in dies, and at last they began to spread in earnest. It was a time when appliance and car makers were increasing investment to catch up with the West, and die and mold shops were adding equipment too^[2].

In this era Japax and Mitsubishi Electric were called the "big two". Japax's D100M descended from the D3, had the largest cumulative sales in the industry, and gained a transistor power supply in 1969. Mitsubishi Electric's Type DM-250 of 1967 moved its spindle with a hydraulic servo and could carry large electrodes of 50 kg. It was designed for sinking blind cavities in forging dies, and became a best seller^[2]. Abroad, the Soviet Union had produced a wire EDM with NC in 1965, and Agie of Switzerland its NC wire EDM, the DEM-15, in 1969^[2].

The Birth of the Wire EDM and NC (1972–1979)

After die-sinking came wire. Using a thin wire as the electrode to cut out contours like a scroll saw, you can cut the punch and die of a blanking (press) die straight from hardened stock, without making electrodes. But moving the wire exactly along the drawing required NC, and because NC was expensive, it took about 20 years from the first Japanese EDM until a wire machine became a product in Japan^[2][10].

1972: DWC-50 and EW-20

In 1972, Mitsubishi Electric released Japan's first wire EDM, the DWC-50 (Type DWC50S-LT1). Instead of expensive NC, it used an optical drawing tracer developed in the US, which followed the lines of a drawing with light and moved the table at reduced scale. It was quick to meet a long-awaited market, and in 2024 it was registered as Essential Historical Materials for Science and Technology (No. 374)^[10][2][11]. Analog tracing had limits on accuracy, however, and the need for digital NC became clear^[2].

In October of the same year, 1972, Seibu Denki Kogyo built the Type EW-20, run by a minicomputer-based NC, and exhibited it at the 6th Japan International Machine Tool Fair. It was Japan's first NC wire EDM, and the company calls it the world's first CNC wire EDM. In 2025 it was registered as Essential Historical Materials for Science and Technology (No. 395)^{[12][2][7][13]}. Wire EDM needs computation-heavy control, such as feeding to match the cutting rate and backing off when a short circuit threatens, so it needed minicomputer or microcomputer NC rather than the relay-based NC of the day^[2]. The same year Mitsubishi Electric also released the DAC-10 and DAC-20 NC units for die-sinking EDMs^[2].

1974: The three makers line up

The 7th Japan International Machine Tool Fair, held in Osaka in 1974, featured Seibu Denki Kogyo's Type EW-30 (microcomputer NC), Mitsubishi Electric's DWC-50M-H (minicomputer NC) and Japax's L250A (minicomputer NC). With NC wire EDMs from the three leading makers of the time all on show, that year marked the start of their widespread adoption^[2]. In die-sinking, too, products appeared such as the UF105C "no-wear electrode power supply", which used transistors to cut electrode wear to 1% or less^[14].

FANUC, Makino and Sodick enter

In 1975 two companies that would later become leading makers entered the field. Fujitsu FANUC (today's FANUC) launched three NC wire EDMs in July, including the TAPECUT MODEL A, with a strategy of winning share through low prices (a newspaper headline of the time: "Selling at less than half the price of competitors")^[2][16]. The TAPECUT SERIES D of 1976 could tilt the wire under CNC to cut the draft (taper) of blanking dies; the database calls it a world first^[18]. Makino Milling Machine formed a technical tie-up with Agie of Switzerland in 1975 and in 1976 began building the DEM-15 wire EDM in Japan^[2].

In August 1976, splitting off from Japax, Sodick was founded in Yokohama^[2][19]. The same year it released SIX-LORAN, Japan's first orbiting device, which moves the electrode slightly in X and Y as well as up and down to give a fine finish on the side walls, and teamed up with Makino Milling Machine to build Japan's first die-sinking EDM with microcomputer NC (machine by Makino, power supply and NC by Sodick)^[2][17]. Makino later ended its tie-ups with both companies and from 1980 built EDMs with its own technology^[2].

Automatic Threading, Higher Precision and the World's Largest Share (1980–1997)

A wire EDM stops if the wire breaks during cutting. Automatically threading a wire of about φ0.2 mm through tight guides and a curved path as long as 1 m is difficult, and from around 1980 makers began offering automatic wire threaders. Japan's first, from FANUC, used technology brought in from Siemens of Germany (1979), and by the mid-1980s the leading makers all had their own. From the start, each maker's unit could also rethread the wire by itself after a break in mid-cut and resume machining where it left off^[2].

More than half of world output

Backed by the growth of mechatronics in Japan and rapidly rising demand for dies and molds, Japanese products caught up with Western ones in performance and had the edge on price. In 1981 Japan's EDM output was 44.6 billion yen, about 50% of an estimated world total of 90 billion yen; in 1984 it was 79.6 billion yen (5,600 units), or 55%^[2]. Wire EDM production rose about tenfold in the ten years from 1975 to 1985, and die and mold shipments grew about fivefold over the same decade^[2]. It was also a period when European makers repeatedly brought patent disputes^[2].

Machines also became faster and more accurate. In 1982 Mitsubishi Electric roughly doubled the maximum cutting rate to 110 mm²/min with its F series, the first in the world to carry a MOSFET power supply, and reached 200 mm²/min with the DWC-90G in 1984^[22]. In 1982 Sodick released the 330W, Japan's first wire EDM able to use oil as the dielectric, to prevent corrosion of cemented carbide^[23]. Makino Milling Machine's EDNC64 die-sinker of 1980 was the first in Japan to adopt a work tank whose three sides drop down, a design that later became the industry standard^[20]. Seibu Denki Kogyo's EWP-300A (1984) was a high-precision machine that used a double-column structure and linear scales to suppress thermal distortion^[24].

From Japax to Sodick

Japax, Japan's top maker until around 1980, struggled after the two oil shocks, and in April 1991 came under Sodick when Sodick took an equity stake. A spin-off taking over its former parent was big news at the time^[2][19]. Japan's total EDM production in units peaked around 1990, after which the strong yen led makers to build plants overseas^[2].

Micro machining and 10-second threading

The 1990s called for dies to make small, light electronic devices. Makino Milling Machine's UPH-1 (1993), built for dies for semiconductor lead frames and the like, used a unique horizontal wire-travel design and was the first in the industry to automatically thread a φ0.03 mm wire. In 2024 it was registered as Essential Historical Materials for Science and Technology (No. 376)^[25][26]. In 1995 Seibu Electric & Machinery cut wire threading time, which had averaged about 90 seconds, to 10 seconds, and "10-second threading" became the target for other makers^[2][7]. Fuzzy control, which captures the intuition of skilled operators, was introduced by Mitsubishi Electric in 1991 and by Sodick in 1993^[2].

★Today: Linear Motors, Micro Machining and New Uses (1998–)

In 1998 Sodick released a die-sinking EDM whose spindle (Z axis) is driven by a linear motor (a world first). It raised the Z-axis speed from a few m/min to 36 m/min, speeding up machining by moving the electrode up and down quickly to flush out debris, and it prompted the whole industry to develop faster Z axes^[27][2]. The 2000s brought features that measure machine temperature and compensate for thermal distortion (Mitsubishi Electric EA8PV ADVANCE, 2008, with guaranteed accuracy of ±3 μm), and controls that automatically change the electrical conditions so that no streaks appear where plate thickness changes (Mitsubishi Electric in 2001, Makino Milling Machine in 2005, and FANUC's "AI Pulse Control 2" in 2009)^[2].

Discharges are used not only to remove metal but also to add it. Since 1998 Mitsubishi Electric has sold EDM surface treatment, which deposits electrode material onto a surface by discharge to form a coating, and in 2013 it announced a machine that slices hard SiC (silicon carbide) into wafers all at once with many wires^[2]. Since the 2010s, network services for monitoring operation and for maintenance and fault diagnosis have come into practical use^[2].

The National Museum of Nature and Science's 2023 survey concludes that the mid-range to high-end world market is shared by GF Machining Solutions of Switzerland (formed from the former Agie and the former Charmilles), ONA of Spain, EXERON of Germany and five Japanese makers (Seibu Electric & Machinery, Sodick, FANUC, Makino Milling Machine and Mitsubishi Electric). Most of the makers that existed in Eastern Europe, the US, the UK, Germany and France have disappeared, while Taiwan and China have many makers of low-cost machines. More than half of Japanese makers' production is now in overseas plants, but the survey sees their global share as remaining high^[2]. In 2024 four machines, the Japaxtron D3, DWC-50, 22-NC and UPH-1, were registered as Essential Historical Materials for Science and Technology, followed by the EW-20 in 2025^{[4][11][21][26][13]}.

What it means on the shop floor. When looking at a used EDM, check: die-sinking or wire; the NC generation (optical tracing, hard-wired, minicomputer, microcomputer); the type of power supply (RC circuit, transistor, MOSFET); whether the dielectric is water or oil; and whether it has automatic threading, and the finest wire it can thread. These tell you the machine's generation and what kinds of dies and parts you can trust it with.