Electric discharge machining machine used

The electrical discharge machining uses electrical discharges to remove material from the workpiece, with each spark producing temperature of about 8000-20000 °C. This causes melting and vaporizing of small volumes of the metal surface and after cooling in the dielectric fluid the melted zones are transformed in recast layer with specific structure. The EDM modified surface consists from two distinctive zones (Kumar et al., 2009 Ho Newman, 2003) ... 

Liquid-phase carbonization occurs for some precursors, such as pitches, which become viscous fluids before carbonization. This process has been used to produce various polycrystalline graphite blocks for steel refining and electrical discharge machining, jigs for the growth of semiconductor crystals, structural components of nuclear reactor, etc. 

Ultrasonic machining (USM) is also of particular importance when very hard type materials are to be cut. As an assist to drilling, HDM energy can extend the drill life when producing holes in reinforced plastics. If the plastic is conductive, electrical discharge machining (EDM) or electrochemical machining (ECM) may be useful. 

Micro electrical discharge machining (EDM) is primarily used for hard metals and other electrically conductive materials. When two electrodes separated by a dielectric medium come close, the dielectrical medium breaks down and suddenly becomes conductive. Sparks generated between the electrodes release energy and remove metal by melting and evaporation [30], Murali and Yeo combined micro electro-discharge machining with ultrasound electrode vibration for improved surface quality, and achieved micro features as small as 25 pm on titanium with 20 pm diameter electrodes [30]. 

W-Cu, V-ThO2). Electrical discharge machining allows close dimensional tolerances, accuracy of form, and a high-quality surface finish to be achieved. Both hardened steels and hardmetals can be machined (Fig. 7.12). Tungsten in wire eroding is not only used as a guide and contact for the wire electrodes, but also as erosion wire. 

FIGURE 7.12. Electrical discharge machining of a compacting die used in the production of gear parts. By courtesy of Plansee AG, Austria. 

The flexible structure can be used to machine metals by electrical discharge machining or polymers by conventional machining. The stiffness of the structure is controlled by the geometry of the four hinges. In the case of circular hinges the overall stiffness K is given by ... 

In some instances, electric discharge machining (EDM) is used. After one face is finished, it is used as the electrode to finish the matching surface. This, too, is slow, expensive, and not always possible. 

Tungsten-copper-boron nitride pseudoalloy electrodes have been tested in electric discharge machining of hard alloys [101,102]. Alloys used in the manufacture of electric contacts are frequently composites of metals and a-BN, providing for increased heat durability [103]. Thus, silver cermet electrical contact material for circuit breakers is made by hot-pressing of the constituents [104 to 106]. Again, Ag/BN composite layers can also be prepared by electrodeposition [107]. Zinc alloys as used in coating sheet steel as anticorrosion layers may contain dipersed a-BN for increased weldability and corrosion resistance [108 to 111]. 

Electrodes for electric discharge machining are partially coated with pyrolytic boron nitride in order to prevent undesirable electric discharge between the electrode and a workpiece [330]. A boron nitride layer is used to prevent bonding of a conductive material, applied for indicating wear, to hard tool ceramics [331]. Equipment for applying pyrolytic boron nitride layers has been described [332], and also for applying boron nitride as protective sheets for immersion pyrometers for molten metals [333]. 

Electrical discharge machining. (EDM) is also commonly performed on molybdenum and its alloys. Care must be exercised when EDMing molybdenum and its alloys because the surface zone frequently contains a resohdified layer. This structure is susceptible to microcracking and should be removed by mechanical or chemical poHshing prior to using the part. 

Fins in the silicon are fabricated in a variety of ways. Argonne National Laboratory uses electrical discharge machining (EDM). MESA+ Research Institute, University of Twente, The Netherlands, uses a KOH etch of the silicon to form the channels [33]. Others use an anisotropical etch of KOH... 

---