Tandem micro electro-discharge machining apparatus

A Tandem-type micro electro-discharge machining (EDM) apparatus, comprising:

• a EDM machining stage including a working zone and an electrode holder spindle, wherein the electrode holder is slid with respect to the working zone;
• a gradation twin-wire EDM device being mounted on the EDM machining stage and slid with reference to the working zone, and further comprising:
• a wire supply reel unit having an upper wire supply reel and a lower wire supply reel;
• a wire take-up reel unit having an upper wire take-up reel and a lower wire take-up reel;
• a stepped insulating roller having an annular upper insulating guide groove and an annular lower insulating guide groove, wherein the upper insulating guide groove has a smaller diameter compared to the lower insulating guide groove, so that the insulating roller is a step-shaped structure, and when the gradation twin-wire EDM device is mounted on the EDM machining stage;
• a twin-wire conductor unit comprising an upper conducting wire and a lower conducting wire, wherein the upper conducting wire is wound around the upper wire supply reel to slide around the upper insulating guide groove and is wound around the upper wire take-up reel, and the lower conducting wire is wound around the lower wire supply reel to slide the lower insulating guide groove and is wound around the lower wire take-up reel;
• and
• a discharge circuit unit consisting of a transistor capacitor(TrC) discharge circuit and a resistor-capacitor (RC) discharge circuit, wherein the TrC discharge circuit is electrically connected to the upper conducting wire for rough machining, and the RC discharge circuit is electrically connected to the lower conducting wire for finish machining;
• a workpiece being mounted on the EDM machining stage and slid with respect to the working zone;
• an electrode tool being assembled to the electrode holder spindle to slide along with the electrode holder with reference to the working zone, wherein the electrode tool is located corresponding to the gradation twin-wire EDM device and the workpiece;
• and
• a RC discharge circuit being electrically connected to the workpiece for micro hole electro-discharge machining.