Today, we launch our “Back to Basics” series. This blog series will serve to provide informative insights on electrical discharging machining (EDM). This will serve as a refresher for experienced operators and as a primer for operators and shop owners just beginning to explore EDM technology and this unique machining process.
The EDM process utilizes short bursts or pulses of electrical energy to erode and machine conductive materials. This process can be thought of as machining with lightning bolts, called sparks. The number and power of each spark can be precisely controlled. By modifying the amount and power of the discharge spark energy, the material removal rate, attained surface finish and resulting accuracy can be predictably and repeatedly controlled.
While EDM is commonly thought of as a slower form of metal removal compared to conventional milling and some other processes, recent advancements in EDM technology have led to significant improvements in processing times and finish quality for even the most complex and involved part geometries. What has now become an essential process for die/mold shops, aerospace, automotive and other manufacturers humbly began with a failure.
In the early 1940s, two scientists in the former Soviet Union, B.R. Butinzky and N.I. Lazarenko, experimented with methods to prevent erosion of tungsten contacts caused by electrical sparking during welding. Although they didn’t find a better welding method, they discovered how to control metal erosion by immersing the electrodes in oil or water. From their research, Butinzky and Lazarenko built the first electrical discharging machine for processing metals that were difficult to machine with conventional milling, drilling or other mechanical methods such as tool steel and titanium.
Butinzky and Lazarenko drew on ideas developed by English physicist, Joseph Priestley, who wrote about the erosive effects of electricity on certain metals back in the 1770s. The Russians’ early work became known as spark machining because electrical discharges caused sparks that could be controlled to manufacture specific shapes.
How Machining with Electricity Works
In conventional machining, the material is removed by cutting tools that turn or grind against the workpiece with a mechanical force. In the EDM process, sparks of electricity create short bursts of high energy that instantly melt and vaporize the material without making contact. Due to the non-mechanical and non-contact machining process, EDM is referred to as a “non-traditional” type of manufacturing.
The key to EDM machining is the passage of electricity from a tool (electrode) to the workpiece, which must be composed of conductive material like steel or aluminum. The tool, which can either be a small diameter wire, hollow tube, or an electrode mechanically machined into a negative version of the workpiece’s final shape, is then placed and maintained in close proximity to the workpiece during the EDM spark erosion process.
Three EDM Methods
EDM technology has evolved into three distinct machining approaches:
Wire EDM: Wire EDM uses a small diameter copper or brass-alloy wire to cut parts much like a band saw. Traditional uses are to make punches, dies, and inserts from hard metals for die/mold tooling applications. Uses have since expanded to include part production uses over a wide array of industries.
Sinker EDM: Sinker EDM uses electrodes machined from a special graphite or copper material into the shape or contour feature needed on the final workpiece. Typically, uses include the production of small or complex cavities and forms for die/mold tooling, but have also found use in many production applications.
EDM Drilling: EDM drilling uses a small diameter hollow tube electrode made from copper or brass alloys to erode holes into the workpiece. This method is typically used to prepare start holes for the wire EDM process, but have also progressed to producing small hole features found in dedicated production applications such as turbine engine components and medical devices.
Stay Tuned for More!
If you’ve enjoyed this Back to Basics lesson, be sure to stay tuned for future updates in this series as we reflect on our industry and celebrate the building blocks that have led to fascinating EDM advancements that we encounter each day.
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