Electrical Discharge Machining
Electrical Discharge Machining (EDM) is a process that uses electrical discharges emitted from an electrode to erode an electrically conductive material. Therefore, it is possible to erode or “burn “electrically the reverse shape of the electrode into the work piece. For example, if a square electrode were used the resultant shape would be a square hole in the work piece.
An EDM system is comprised of a dielectric reservoir and work tank, as well as a pump and filtering system. The electronic components include the pulse generator and control system for the Z axis servo.
The work piece is placed in the work tank which is filled with a hydrocarbon dielectric. A pulsed electrical field is between the electrode and the work piece (known as the gap). The small (few thousandths of an inch at most) gap becomes conductive in the presence of an electrical field. For the gap to become conductive the applied voltage is usually on the order of 100VDC
The automated servo control system maintains the appropriate separation of the electrode and work piece. As each spark is discharged from the electrode (the cutting tool) to the work piece, a small amount of metal is vaporized and a crater is left in the work piece. The dielectric fluid quickly cools the vaporized metal and removes it from the gap area. The solidified metal partials are trapped in the filtering system.
The EDM process is repeated thousands (even millions) of times each second. It is possible to erode virtually any shapes into materials that will conduct electricity; even some semiconductor materials may be machined via this process. Generally speaking, the hardness of the work piece has little effect on the ability to erode it; this is one of the biggest advantages of the EDM process.
Most EDM machines are large commercial units that cost many thousands of dollars and occupy quite a large footprint in the shop. There are few, if any, affordable bench top machines available for home or small machine shop applications. It is my intent to fill this void by providing information on building a bench top size EDM which has the capability of performing real work and is reasonable in cost.
On this web site you will find information on how to build and operate your own bench-top EDM
I hope you find the site an exciting learning experience, and a way to get involved in building your own ram type EDM.