Aerospace edm Electro Discharge Machining

Electro Discharge Machining EDM, sometimes known  as spark machining or spark erosion, is used in aerospace as a cnc machining method for hard metals or those that would be impossible to machine with traditional techniques. EDM only works with materials that are electrically conductive. EDM can, for example, cut small or shaped angles, intricate contours or cavities in pre-hardened steel.

Aerospace machining of steel with alloying elements such as manganese, chromium, vanadium, and tungsten, exotic metals such as titanium, hastelloy (a range of twenty two different highly corrosion-resistant metal alloys), kovar, inconel (Inconel is a family of austenitic nickel-chromium-based superalloys typically used in high temperature applications) all use this process.

EDM removes material by a series of rapid-fire recurring electrical arcing discharges between an electrode and the workpiece. An energetic electric field is created. The EDM cutting tool is guided along the desired path very close to the work but it does not touch the piece. Consecutive sparks produce a series of micro-craters on the work piece and remove material along the cutting path by melting and vaporization.

The particles are washed away by the continuously flushing dielectric fluid. It is also important to note that a similar micro-crater is formed on the surface of the electrode, the debris from which must also be flushed away. In fact, EDM is sometimes described as the process of removing material from two electrodes, the workpiece and the tool. These micro-craters result in the gradual erosion of the electrode, which, in the case of wire EDM machining, has to be constantly replaced from a spool.

EDM grinding is a very similar process, and uses a rotating conductive wheel to remove electrically conductive material by means of controlled, repetitive spark discharges. A dielectric fluid is used to flush away the chips, regulate the discharge, and cool the wheel and the workpiece.

There are two main types of EDM machines: Conventional EDM and Wire EDM. Conventional EDM is becoming a common method of making aerospace prototypes and aircraft production parts. In the early days, the efficiency of removing the deposits and hence, the surface integrity of the component, was questioned, but the technology has been refined beyond that point now.

Small hole drilling EDM is used to make a through hole in a workpiece and is one of the many variations on the original EDM concept that have been developed.

Aerospace Wire Erosion. 

Wire electro discharge machining (WEDM), or wire-cut EDM is used to cut plates and to fashion hard metals that are too difficult to machine with other methods. A hole or perforation must already be made in the metal which is usually done by small hole EDM.

The wire is then fed through the hole. There is never any mechanical contact between the electrode and workpiece. The wire is usually made of brass or stratified copper, and is between 0.1 and 0.3 mm diameter.

Wire-cutting EDM advantages include low work holding forces, low cutting forces, accurate process tolerances, no tool wear (the wire is continually replenished), small corners and narrow slots. The main disadvantage remains removing the unwanted material.