Electrical discharge machining (EDM) is a process that is used on electrically conductive metals to produce molds and certain complex metal parts. It is most effectively used on hard metals that cannot be machined by traditional methods, including hardened tool-steel, carbide and titanium.
Electrical discharge machining, which is oftentimes referred to as “spark machining” because of the electrical discharges being produced as the metal is cut, is able to cut precise patterns and forge delicate cavities in metal that cannot be done through using a grinder or an end mill. It works by allowing an electrical pulse to travel between an electrode and the piece of metal, which cuts away the metal a little at a time, until the desired shape is produced. There are two primary electrical discharge machining methods: wire EDM and ram EDM.
Ram EDM involves machining a graphite electrode with traditional cutting tools into a shape specific to the product being molded. Then the electrode is connected to a power source and fed into a work piece. The whole process is completed under fluid in order to flush material away and cool the metal surrounding the cut zone (this minimizes damage to the piece.) The fluid also serves as a conductor for current to pass between the piece being worked and the electrode.
In wire electrical discharge machining, a common electrode is not used. Instead, a special wire (usually made of brass) serves as the electrode. The product, which is usually placed in water to allow for constant cooling of the material, is cut by way of the electrical discharge between the wire and the product as the wire is fed through the material. If it could be observed closely, one would find that the wire itself never comes into contact with the material. Instead, the electrical discharges remove the material enough for the wire to move through the piece. Wire EDM is controlled by computer, allowing for some of the most complicated shapes to be created.
Because it is often a computer-run process, electrical discharge machining allows for the design and production of an unlimited complexity and variety of shapes. It has now become a standard method of producing prototypes and molds.