What is the History of Electro Arc and EDM?

When you search for the term “metal disintegrator” you will likely find ‘Electrical discharge machining’ as a result.  That is because the technological breakthrough that led to metal disintegrating machines was spearheaded by a team including Harold Stark who went on to patent the idea for AC metal disintegrators and started the world’s first metal disintegration machine factory in Detroit Michigan.  This process is metal disintegration machining (MDM).

You may have heard Electrical discharge machining, EDM for short, called spark machining, arc machining, and spark eroding.  This is a non-conventional group of machining which now includes electrochemical machining, water jet cutting, and laser cutting.  This process is limited to use with ferrous alloys because it requires the base material to be electrically conductive.  A solution for high accuracy, complex machining applications provides an efficient alternative where other methods are impossible.  Using an electrical current, spark discharge erodes the workpiece using dielectric fluid as an electrical insulator. There are three main forms of EDM, wire EDM, die sinker EDM, and hole popping EDM.  

EDM is usually associated with the wire EDM machine method which was developed between the 1960s and 70s to make dies from hardened steel.  This EDM process uses wire wound between two spools of wire creating two electrodes, the tool-electrode, and workpiece-electrode, which are separated by dielectric fluid. With increased voltage, the fluid produces an electric arc. The wire moves in a controlled pattern and sparking occurs between the wire and the workpiece.  This method removes excess material with automated technology similar to CNC providing high accuracy and precision.  Commercial wire EDM capability has continued to advance substantially over the last few decades.

Joseph Priestly originally discovered the erosive effect of electrical discharges in 1770.  Die sinker EDM was invented independently by two groups.  In 1943 two Russian scientists Boris and Natalya Lazarenko were exploring methods to increase the lifespan of tungsten breaker points. Their research led to the discovery that erosion could be precisely controlled if the electrodes were immersed in dielectric fluid. This allowed the invention of an EDM machine tool for processing hard materials like Tungsten. This tool became known as a resistor-capacitor (R-C) circuit for EDM.  

During this time, without knowledge of the experimentation taking place in Russia, a team of American scientists consisting of Harold Stark (the founding president of Electro Arc), Victor Harding and Jack Beaver were also developing a method to remove broken drills and taps from aluminum castings.  This team was tasked by their employer with finding a solution because tools were being broken off in expensive aircraft parts.  Initially constructing machines from electric etching tools, they were unsuccessful.  After trying compressed air, they added fluid to the machines, combined with spark repetition allowing them to cut through metal quickly and efficiently while the coolant flushed away metal particles created in this process. Their research was able to produce 60 sparks per second, a breakthrough in technology at the time. Machines initially developed by this team were used during World war II and the trio patented the system for removing broken bolts, taps, and drills as well as an electronic-circuit servo system that maintained proper spacing between the electrode and the workpiece.

This led Harold Stark to develop Electro Arc’s Metal Disintegrator line of metal disintegrating machines which are still produced by Stillion Industries today (Stillion Industries purchased Electro Arc in 2019).  This technology was key in the development of vacuum tube EDM machine tools capable of producing thousands of sparks per second (electric discharge machining) in the 1960s.  Die sinker EDM machines are traditionally used to create three-dimensional shapes.  EDM provides an advantage because the process is predictable and accurate, making it easy to reproduce, but it is slower than other methods.

Hole drilling EDM is a specialized hole-making machine sometimes called a “hole popper” which is used to create the pilot hole necessary for wire threading. Using thermal energy rather than mechanical force, these machines cut through extremely hard materials such as titanium, carbide, carbon graphite, and high alloy steel.  These machines work on the same principle as wire EDM machines.  Instead of wire, these machines use a tool that works like a drill bit, no physical contact takes place between the tool and the workpiece, the electrical discharge is conducted to rapidly cut the metal.  This process is ideal for extremely small holes, as small as 0.010”. 

In his book, ‘Electrical Discharge Machining’ Elman C. Jameson mentions working with Victor Harding and Harold Stark during the origination of the EDM process in the United States.  EDM became popular in Japan as a result of damage from the war.  This new method was key in rebuilding after the destruction of their infrastructure.  On the other hand, The existing equipment and workers in the US caused a delay in the acceptance of EDM technology in the US.  Electro Arc metal disintegrators are an appealing option because they do not require special training for operators as other EDM machines require.

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