1.1 WIRE EDM

 

• 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