What is

Electrical Discharge Machining?


Pulse Supply

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 workpiece. For example, if a square electrode were used  the resultant shape would be a square hole in the workpiece.

EDM Work tank & Servo head
EDM Work tank & Servo head

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 the Z axis servo.

The workpiece is placed in the work tank which is filled with a hydrocarbon dielectric.  A pulsed electrical field is  between the electrode and the workpiece (known as the gap). The small (a couple of 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

Servo head
Servo head

The automated servo control system maintains the appropriate  separation of the electrode and workpiece.  As each spark is discharged from the electrode (the cutting tool) to the workpiece, a small amount of metal is vaporized and a crater is left in the workpiece. 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 workpiece has little effect on the ability to erode it; this is one of the biggest advantages of the EDM process.

On this web site you will find information on how to build  and operate your own EDM.

Most EDM machines are large commercial units that cost many thousands of dollars and occupies 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 reasonable in cost. I hope you find the site a learning experience, and a way to get involved in building your own ram type EDM.