59.1 WIRE EDM

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A thin wire of brass, tungsten, or copper is used as an electrode.

Deionized water is used as the dielectric.

The process is similar to standard EDM,

Slowly cuts groove in shape of wire.

Wire is consumed and is slowly fed.

This process is much faster than electrode EDM.

Machine speed is,

Higher currents, and lower rest times increase the speed of this process.

Relations between groove width and speed are shown in the graph below.

This process is well suited to production of dies for plastic molding, progressive dies, etc.

Summary of EDM characteristics,

- mechanics of material removal - melting and evaporation aided by cavitation

- medium - dielectric fluid

- tool materials - Cu, Brass, Cu-W alloy, Ag-W alloy, graphite

- material/tool wear = 0.1 to 10

- gap = 10 to 125 micro m

- maximum mrr = 5*103 mm3/min

- specific power consumption 1.8 W/mm3/min

- critical parameters - voltage, capacitance, spark gap, dielectric circulation, melting temperature

- materials application - all conducting metals and alloys

- shape application - blind complex cavities, microholes for nozzles, through cutting of non-circular holes, narrow slots

- limitations - high specific energy consumption (about 50 times that in conventional machining); when forced circulation of dielectric is not possible, removal rate is quite low; surface tends to be rough for larger removal rates; not applicable to nonconducting materials