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Encyclopedia > Electrical discharge machining
Electrical Discharge Machine
Electrical Discharge Machine

Electrical discharge machining (or EDM) is a machining method primarily used for hard metals or those that would be impossible to machine with traditional techniques. One critical limitation, however, is that EDM only works with materials that are electrically conductive. EDM can cut small or odd-shaped angles, intricate contours or cavities in pre-hardened steel without the need for heat treatmentment to soften and re-harden them as well as exotic metals such as titanium, hastelloy, kovar, inconel and carbide. Image File history File links Electrical-discharge-machine. ... Image File history File links Electrical-discharge-machine. ... The steel cable of a colliery winding tower. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... HASTELLOY is the registered trademark name of Haynes International, Inc. ... Kovar is a nickel-cobalt ferrous alloy designed to be compatible with the thermal expansion characteristic of sealing to borosilicate glass. ... Inconel® is a registered trademark of Special Metals Corporation referring to a family of austenitic nickel-based superalloys. ... Calcium carbide. ...


Sometimes referred to as spark machining or spark eroding, EDM is a nontraditional method of removing material by a series of rapidly recurring electric arcing discharges between an electrode (the cutting tool) and the work piece, in the presence of an energetic electric field. 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. These micro craters result in the gradual erosion of the electrode, many times necessitating several different electrodes of varying tolerances to be used, or, in the case of wire EDM machining, constant replacement of the wire by feeding from a spool. Electricity arcs between the power rail and electrical pickup shoe on a London Underground train An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, similar to the instant spark, resulting from a current flowing through normally nonconductive media such as air. ... An electrode is an electrical conductor used to make contact with a metallic part of a circuit (e. ... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... Evaporation is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state. ... Cutting fluid or coolant is liquid used to cool and lubricate the cutting edges of machine tools and the pieces they are shaping. ...


There are two main types of EDM machines: Conventional EDM (also called Sinker EDM and Ram EDM) and Wire EDM.

Contents

Advantages

Some of the advantages of EDM include machining of complex shapes that would otherwise be difficult to produce with conventional cutting tools, machining of extremely hard material to very close tolerances, and machining of very small work pieces where conventional cutting tools may damage the part from excess cutting tool pressure.


Disadvantages

Some of the disadvantages of EDM include the inability to machine non conductive materials, the slow rate of material removal, and the additional time and cost used for creating electrodes for ram EDM.


Conventional EDM

Prototype production

The EDM process is most widely used by the mold-making tool and die industries, but is becoming a common method of making prototype and production parts, especially in the aerospace,automobile and electronics industries in which production quantities are relatively low. In ram EDM, a graphite or pure copper electrode is machined into the desired (negative) shape and fed into the workpiece on the end of a vertical ram. A die is a tool used in the manufacturing industry to create a wide variety of products and components. ... Graphite (named by Abraham Gottlob Werner in 1789 from the Greek γραφειν (graphein): to draw/write, for its use in pencils) is one of the allotropes of carbon. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ...


Coinage die making

For the creation of dies for producing jewelry and badges by the coinage (stamping) process, the positive master may be made from sterling silver, since (with appropriate machine settings) the master is not significantly eroded and is used only once. The resultant negative die is then hardened and used in a drop hammer to produce stamped flats from cutout sheet blanks of bronze, silver, or low proof gold alloy. For badges these flats may be further shaped to a curved surface by another die. This type of EDM is usually performed submerged in an oil-based dielectric. The finished object may be further refined by hard (glass) or soft (paint) enameling and/or electroplated with pure gold or nickel. Softer materials such as silver may be hand engraved as a refinement.

EDM control panel (Hansvedt machine). Machine may be adjusted for a refined surface (electropolish) at end of process.
EDM control panel (Hansvedt machine). Machine may be adjusted for a refined surface (electropolish) at end of process.
Master at top, badge die workpiece at bottom, oil jets at left (oil has been drained). Initial flat stamping will be "dapped" to give a curved surface
Master at top, badge die workpiece at bottom, oil jets at left (oil has been drained). Initial flat stamping will be "dapped" to give a curved surface

Image File history File links Download high-resolution version (1340x1430, 463 KB)Hansvedt EDM machine controls. ... Image File history File links Download high-resolution version (1340x1430, 463 KB)Hansvedt EDM machine controls. ... Image File history File links Download high-resolution version (1224x1480, 645 KB)Making a coinaage die using EDM process. ... Image File history File links Download high-resolution version (1224x1480, 645 KB)Making a coinaage die using EDM process. ...

Small hole drilling EDM

Is used to make a through hole in a workpiece in through which to thread the wire in Wire-cut EDM machining. The small hole drilling head is mounted on wire-cut machine and allows large hardened plates to have finished parts eroded from them as needed and without pre-drilling. There are also stand-alone small hole drilling EDM machines with an xy axis also known as a super drill or hole popper that can machine blind or through holes . EDM Drills bore holes with a long brass or copper tube electrode that rotates in a chuck with a constant flow of distilled or deionized water flowing through the electrode as a flushing agent and dielectric. The electrode tubes operate like the wire in wire cut EDM machines, having a spark gap and wear rate. Some small hole drilling EDM's are able to drill through 100mm of soft or through hardened steel in less than 10 seconds, averaging %50 to %80 wear rate. Holes of Ø 0.3mm to Ø6.1mm can be achieved in this drilling operation. Brass electrodes are easier to machine but are not recommended for wire-cut operations due to eroded brass particles causing ' 'Brass on Brass' 'wire breakage, therefore copper is recommended. Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. ...


Wire Cut EDM

In wire electrical discharge machining (WEDM), or wire-cut EDM, a thin single-strand metal wire, usually brass, is fed through the workpiece, typically occurring submerged in a tank of dielectric fluid. The wire, which is constantly fed from a spool, is held between upper and lower diamond guides. The guides move in the xy plane, usually being CNC controlled and on almost all modern machines the upper guide can also move independently in the zuv axis, giving rise to the ability to cut tapered and transitioning shapes (circle on the bottom square at the top for example)and can control axis movements in xyuvijkl–. This gives the wire-cut EDM the ability to be programmed to cut very intricate and delicate shapes. The wire is controlled by upper and lower diamond guides that are usually accurate to 0.004mm, and can have a cutting path or kerf as small as 0.12mm using Ø 0.1mm wire, though the average cutting kerf that achieves the best economic cost and machining time is 0.335mm using Ø 0.25 brass wire. The reason that the cutting width is greater than the width of the wire is because sparking also occurs from the sides of the wire to the work piece, causing erosion. This "overcut" is necessary, predictable, and easily compensated for. Spools of wire are typically very long. For example, an 8 Kg spool of Ø0.25mm wire is just over 19 kilometers long. Today, the smallest wire diameter is 20 microns and the geometry precision is not far from +/- 1 micron. The wire-cut process uses water as its dielectric with the water's resistivity and other electrical properties carefully controlled by filters and de-ionizer units. The water also serves the very critical purpose of flushing the cut debris away from the cutting zone. Flushing is an important determining factor in the maximum feed rate available in a given material thickness, and poor flushing situations necessitate the reduction of the feed rate. A CNC Turning Center A CNC Milling Machine The abbreviation CNC stands for computer numerical control, and refers specifically to a computer controller that reads G-code instructions and drives the machine tool, a powered mechanical device typically used to fabricate metal components by the selective removal of metal. ... An electrostatic potential map of the nitrate ion (NO3−). Areas coloured red are lower in energy than areas colored yellow An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged. ...

See also

Electro Chemical Machining (or ECM) is a method of working extremely hard materials or materials that are difficult to machine cleanly using conventional methods. ... Injection molding is a manufacturing technique for making parts from thermoplastic material in production. ...

External links

  • Research carried on EDM process
  • New Arc Detection Technology for Highly Efficient Electro-Discharge Machining


Metalworking:

 Milling and machining: Image File history File links This is a lossless scalable vector image. ... Turned chess pieces Metalworking is the craft and practice of working with metals to create structures or machine parts. ...

Electrical discharge machining | Electro chemical machining | Endmill | Engraving | Hobbing machine | Lathe | Machine tool | Machining | Milling cutter | Milling machine | Planer | Pantograph | Shaper

Metalworking topics:   Electro Chemical Machining (or ECM) is a method of working extremely hard materials or materials that are difficult to machine cleanly using conventional methods. ... Several types of endmills An endmill is a type of Milling cutter, a cutting tool used in industrial milling applications. ... Engraving is the practice of incising a design onto a hard, flat surface, by cutting grooves into it. ... A hobbing machine is a special form of milling machine that mills gears. ... Center lathe with DRO and chuck guard. ... A machine tool is a powered mechanical device, typically used to fabricate metal components of machines by machining, which is the selective removal of metal. ... A lathe is a common tool used in machining. ... Milling cutters are cutting tools used in milling machines or machining centres. ... Endmills for a milling machine. ... A metalworking planer is a type of metalworking machine tool, analogous to a shaper but larger and with the entire workpiece moving beneath the cutter. ... Shaper tool slide, clapper box and cutting tool A shaper is a machine tool used for shaping or surfacing metal and other materials. ... Turned chess pieces Metalworking is the craft and practice of working with metals to create structures or machine parts. ...

Casting | CNC | Cutting tools | Drilling and threading | Fabrication | Finishing | Grinding | Jewellery | Lathe (tool) | Machining | Machine tooling | Measuring | Metalworking | Hand tools | Metallurgy | Milling | Occupations | Press tools | Smithing | Terminology | Welding Casting may be used to create artistic sculptures Casting is a manufacturing process by which a molten material such as metal or plastic is introduced into a mold, allowed to solidify within the mold, and then ejected or broken out to make a fabricated part. ... A CNC Turning Center A CNC Milling Machine The abbreviation CNC stands for computer numerical control, and refers specifically to a computer controller that reads G-code instructions and drives the machine tool, a powered mechanical device typically used to fabricate metal components by the selective removal of metal. ... a Cutting Tool, in the context of Metalworking is any tool that is used to remove metal from the workpiece by means of shear deformation. ... Drilling is the process of using a drill bit in a drill to produce holes. ... A typical steel fabrication shop Fabrication, when used chas an industrial term, applies to the building of machines and structures by cutting, shaping and assembling components made from raw materials. ... Metalworking finishing is the activity of making things out of metal in a skillful manner. ... Rotating abrasive wheel on a bench grinder. ... Amber jewellery in the form of pendants Jewellery (also spelled jewelry, see spelling differences) is a personal ornament, such as a necklace, ring, or bracelet, made from jewels, precious metals or other substance. ... Conventional metalworking lathe In woodturning, metalworking, metal spinning, and glassworking, a lathe is a machine tool which spins a block of material so that when abrasive, cutting, or deformation tools are applied to the block, it can be shaped to produce an object which has rotational symmetry about an axis... A lathe is a common tool used in machining. ... A machine tool is a powered mechanical device, typically used to fabricate metal components of machines by the selective removal of metal. ... The examples and perspective in this article or section may not represent a worldwide view. ... Turned chess pieces Metalworking is the craft and practice of working with metals to create structures or machine parts. ... Metalworking hand tools are hand tools that are used in the metalworking field. ... Metallurgy is a domain of materials science and of materials engineering that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. ... Endmills for a milling machine. ... It has been suggested that this article or section be merged with Smith (metalwork). ... Power press with a fixed barrier guard A press, or a machine press is a tool used to work metal (typically steel) by changing its shape and internal structure. ... A smith, or metalsmith, is a person involved in the shaping of metal objects. ... This article needs to be wikified. ... Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ...


  Results from FactBites:
 
High speed electrical discharge machining by redressing high resolution graphite electrodes - Patent 4754115 (3716 words)
Electrical discharge machining has grown to be the preferred machining technique for a variety of production machining procedures, including the production of molds, dies, and complex three-dimensional workpieces, particularly those of difficult to machine materials.
If electrical discharge machining parameters are chosen to keep electrode wear to the minimal levels attainable, often referred to in the art by the misnomer "zero wear conditions" in a collective conspiracy of wishful thinking, the electrode will still have one part wear for each one hundred parts of stock removal from the workpiece.
Machining is effected by a combination of the mechanical action of abrasive grains projected against the surface of the workpiece and cavitation in the liquid.
What is EDM (Electrical Discharge Machining)? (553 words)
EDM is a machining method primarily used for hard metals or those that would be impossible to machine with traditional techniques.
EDM or Electrical Discharge Machining, is especially well-suited for cutting intricate contours or delicate cavities that would be difficult to produce with a grinder, an end mill or other cutting tools.
If you were to observe the wire EDM process under a microscope, you would discover that the wire itself does not actually touch the metal to be cut; the electrical discharges actually remove small amounts of material and allow the wire to be moved through the workpiece.
  More results at FactBites »

 
 

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