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EDM Work, Light Manufacturing, Sinker EDM, Wire EDM, Small Hole EDM & Support Capabilities

Definition of EDM

EDM - Sinker

Electrical discharge machining (EDM), sometimes referred to as spark machining, is a nontraditional method of removing metal by a series of rapidly recurring electrical discharges between an electrode (the cutting tool) and the workpiece in the presence of a dielectric field. The ensuing minute metal chips are removed by melting and vaporization, and are washed away by the continuously flushing dielectric fluid. EDM can cut materials regardless of their hardness or toughness, but is limited to the machining of electrically conductive workpiece materials.

The EDM process is most widely used by the mold-making tool and die industries, but is increasingly applied to make prototype and production parts, especially in the aerospace and electronics industries in which production requirements are relatively low. EDM is particularly well suited for parts which are made from materials that are difficult to machine and/or contain small or odd-shaped angles, intricate cavities or intricate contours.

There are two major types of EDM, Wire EDM and Sinker EDM (sometimes called Ram or Conventional EDM). The main difference between the two is the type of electrode used. Wire EDM, as its name suggests, uses wire as the electrode. Certain parts can only be produced using sinker EDM, which, unlike wire EDM, does not cut all the way through the part. As its name implies, Sinker EDM literally "sinks" a required shape into the workpiece.

Wire EDM

Wire electrical discharge machining (WEDM), also known as wire-cut EDM is a process of using a thin single-strand of metal wire fed through a workpiece. The wire is constantly fed from a spool the is held between upper and lower guides. The guides move in the x–y plane and control the movement of the wire through the workpiece during the cutting process. Most machines in use today are CNC controlled. Wire EDM machines are very precise and can be programmed to cut very intricate and delicate shapes.

The wire-cut process uses water as its dielectric with the water's resistivity and other electrical properties carefully controlled by filters and deionizer units. The water also serves the very critical purpose of flushing the cut debris away from the cutting zone. Flushing is an important determining factor in the maximum feed rate available in a given material thickness, and poor flushing situations necessitate the reduction of the feed rate.

Small Hole EDM

Is used to make a through hole in a workpiece in through which to thread the wire in Wire-cut EDM machining. The small hole drilling head is mounted on wire-cut machine and allows large hardened plates to have finished parts eroded from them as needed and without pre-drilling. There are also stand-alone small hole drilling EDM machines with an x–y axis also known as a super drill or hole popper that can machine blind or through holes. EDM Drills bore holes with a long brass or copper tube electrode that rotates in a chuck with a constant flow of distilled or deionized water flowing through the electrode as a flushing agent and dielectric.

The electrode tubes operate like the wire in wire-cut EDM machines, having a spark gap and wear rate. Some small-hole drilling EDMs are able to drill through 100 mm of soft or through hardened steel in less than 10 seconds, averaging 50% to 80% wear rate. Holes of 0.3 mm to 6.1 mm can be achieved in this drilling operation. Brass electrodes are easier to machine but are not recommended for wire-cut operations due to eroded brass particles causing "brass on brass" wire breakage, therefore copper is recommended.

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