Electrical discharge machining (EDM)

To understand how ADM 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  contaminants suspended in the dielectric .

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 and  vaporizes from the electrode and work  piece at the points of spark contact a  bubble composed of gaseous byproducts of  vaporization rapidly expands outward  from the spark channel.

Once the pulse  ends the spark and heating actions stop  collapsing the spark channel dielectric  fluid then rushes into the gap flushing  molten material from both surfaces this  EDM residue consists 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 enhance  metallurgical structure this layer can  be reduced using the right control  settings or by polishing the part the  third layer is the heat affected zone or  annealed layer it has only been heated  not melted.

In RAM EDM machines the  workpiece mounts inside a tank and is  covered with dielectric fluid an  electrode then lowers to  within a few thousandths of an inch of  the workpiece to begin EDM a ram type  pdms have the ability to produce complex  cavities out of a solid piece of metal  Ram EDM machines are also referred to as  dye sinkers or vertical EDM and range in  size and automation from manually  operated tabletop systems to 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 use a  travelling wire electrode to cut complex  outlines and fine details in stamping  and blanking dies of pre hardened tool  steel the wire drive system continuously  delivers fresh wire under constant  tension to the work area guided by a set  of sapphire or diamond wire guides new  wire is always exposed to the part so  electrode wear isn't a problem like in  RAM EDM ik wire EDM machines are also  easier to learn than Ram EDM.

They can  run unattended for long periods  including overnight and weekends there  are four basic wire EDM subsystems all  of which are CNC controlled those  subsystems include the power supply the  dielectric system the wire feeding  system and the positioning system...