Electro discharge machine (EDM)

to understand how EDM removes metal let's examine a single spark in the erosion process as a pulse of dc electricity reaches the electrode and part an intense electrical field develops in the gap microscopic contaminant suspended in the dialectic fluid are attracted by the field and concentrate at the field strongest point these contaminants build a high conductivity bridge across the gap as the fields voltage increases this material in the conductive bridge heats up some pieces ionized to form a spark channel between the electrode and the work piece at this point both the temperature and pressure in the channel rapidly increase generating a spark. a small amount of material melts in vaporizes from the electrode and workpiece at the points a spark contact .a bubble composed of gaseous by-products of vaporization rapidly expands outward from the spark channel. once the poll ends the spark and heating action stop collapsing the spark channel di electric fluid ben rushes into the gap flushing molten material from both surfaces. these EDM residue consist of small solidified balls of material and gas bubbles.
              the resulting EDM part can have several observable surface layers the top surface layer is created when expelled molten metal and small amounts of electrode material form spheres and spatter the surface. this layer is easily removed. the next layer is a recast or white layer where EDM ng has altered the workpiece metallurgical structure this layer can be reduced using the right control settings or by polishing the park. the third layer is that he defected zone or annealed later it has only been heeded not melted.
         in ram EDM machines the workpiece mounts inside a tank and is covered with dielectric fluid and electrod then lowers to within a few thousands of an inch of the workpiece to begin EDM inc ram EDM have the ability to produce complex cavities out of a solid piece of metal ram EDM machines are also referred to as diesinkers or vertical EDM and range in size and automation from manually operated tabletop systems a large bed manual or computer numerical control systems.
              a ram EDM has four major subsystems a power supply a dielectric system an electrode and a servo system cnc wire cut EDM machines user traveling wire electrode to cut complex outlines and fine details in stamping and blanking dies of prehardened tool steel               the wire drive system continuously delivers fresh wire under constant tension to the work area guided by a set of satsphire or diamond wire guides new wire is always exposed to the part so electrode where isn't a problem like in ram EDM.
      wire EDM machines are also easier to learn and ram EDM they can run unattended for long periods including overnight and weekends there are four basic wire EDM subsystems all of which are cmc controlled knows some systems include the power supply the die electric system the wire feeding system and the positioning system

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