Electrical Discharge Machining : Electrical Discharge Machining Slide 2: Electrical discharge machining is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques. EDM typically works with materials that are electrically conductive, although methods for machining insulating ceramics with EDM have also been proposed. EDM can cut intricate contours or cavities in pre-hardened steel without the need for heat treatment to soften and re-harden them. This method can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel. INTRODUCTION Slide 3: Electrical discharge machining (EDM)
Based on erosion of metals by spark discharges.
EDM system consist of a tool (electrode) and work piece, connected to a dc power supply and placed in a dielectric fluid.
when potential difference between tool and work piece is high, a transient spark discharges through the fluid, removing a small amount of metal from the work piece surface.
This process is repeated with capacitor discharge rates of 50-500 kHz. Slide 4: dielectric fluid – mineral oils, kerosene, distilled and deionized water etc.
role of the dielectric fluid
1. acts as a insulator until the potential is sufficiently high.
2. acts as a flushing medium and carries away the debris.
3. also acts as a cooling medium.
Electrodes – usually made of graphite.
EDM can be used for die cavities, small diameter deep holes,turbine blades and various intricate shapes. Electrical Discharge Machining : Electrical Discharge Machining Electrical-Discharge Machining : Electrical-Discharge Machining Fig : (a) Schematic illustration of the electrical-discharge machining process. This is one of the most widely used machining processes, particularly for die-sinking operations. (b) Examples of cavities produced by the electrical-discharge machining process, using shaped electrodes. Two round parts (rear) are the set of dies for extruding the aluminum the aluminum piece shown in front. (c) A spiral cavity produced by ECM using a slowly rotating electrode, similar to a screw thread. (a) (b) (c) Examples of EDM : Examples of EDM Fig : Stepped cavities produced with a square electrode by the EDM process. The workpiece moves in the two principal horizontal directions (x-y), and its motion is synchronized with the downward movement of the electrode to produce these cavities. Also shown is a round electrode capable of producing round or elliptical cavities. Fig : Schematic illustration of producing an inner cavity by EDM, using a specially designed electrode with a hinged tip, which is slowly opened and rotated to produce the large cavity. WIRE EDM : WIRE EDM Fig : (a) Schematic illustration of the wire EDM process. As much as 50 hours of machining can be performed with one reel of wire, which is then discarded. (b) Cutting a thick plate with wire EDM. (c) A computer-controlled wire EDM machine. WIRE EDM : WIRE EDM Slide 10: Wire EDM
This process is similar to contour cutting with a band saw.
a slow moving wire travels along a prescribed path, cutting the work piece with discharge sparks.
wire should have sufficient tensile strength and fracture toughness.
wire is made of brass, copper or tungsten. (about 0.25mm in diameter). Slide 11: Applications:-
Coinage die making
Small hole drilling Slide 12: THANK YOU!!!!!!!