先进制造技术-EDM技术演示文稿(学生做).ppt

Electrical Discharge Machining（EDM）,Advanced Manufacturing Technology,What Is EDM？,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 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. Metals that can be machined with EDM include hastalloy, hardened tool-steel, titanium, carbide, inconel and kovar. EDM is sometimes called “spark machining“ because it removes metal by producing a rapid series of repetitive electrical discharges. These electrical discharges are passed between anelectrode and the piece of metal being machined. The small amount of material that is removed from the workpiece is flushed away with a continuously flowing fluid. The repetitive discharges create a set of successively deeper craters in the work piece until the final shape is produced. There are two primary EDM methods: ram EDM and wire EDM. The primary difference between the two involves the electrode that is used to perform the machining. In a typical ram EDMapplication, a graphite electrode is machined with traditional tools. The now specially-shaped electrode is connected to the power source, attached to a ram, and slowly fed into the workpiece. The entire machining operation is usually performed while submerged in a fluid bath. The fluid serves the following three purposes:,Advanced Manufacturing Technology,Electrical Discharge Machining（EDM）,flushes material away serves as a coolant to minimize the heat affected zone, thereby preventing potential damage to the workpiece acts as a conductor for the current to pass between the electrode and the workpiece.,Advanced Manufacturing Technology,Electrical Discharge Machining（EDM）,In wire EDM a very thin wire serves as the electrode. Special brass wires are typically used; the wire is slowly fed through the material and the electrical discharges actually cut the workpiece. Wire EDM is usually performed in a bath of water. If someone was to observe the wire EDM process under a microscope, he 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. The path of the wire is typically controlled by a computer, which allows extremely complex shapes to be produced. Perhaps the best way to explain wire EDM is to use an analogy. Imagine a thin metal wire stretched between two hands, slid though a block of cheese, cutting any shape desired. The positions of the hands can be alterred on either side of the cheese to define complex and curved shapes. Wire EDM works in a similar fashion, except electrical discharge machining can handle some of the hardest materials used in industry. Also note that, in dragging a wire through cheese, the wire is actually displacing the cheese as it cuts, but in EDM, a thin kerf is created by removing tiny particles of metal. Electrical discharge machining is frequently used to make dies and molds. It has recently become a standard method of producing prototypes and some production parts, particularly in low volume applications. For more details regarding a typical application, you can read about acustom bronze branding-iron that was made with EDM.,Advanced Manufacturing Technology,Electrical Discharge Machining（EDM）,Advanced Manufacturing Technology,Die-sinking EDM systems, the electrode (cutting tool) and workpiece are held by the machine tool. The power supply controls the electrical discharges and movement of the electrode in relation to the workpiece. During operation the workpiece is submerged in a bath of dielectric fluid (electrically nonconducting). (Die-Sinking EDM is also called Sinker, Ram-Type, Conventional, Plunge or Vertical EDM),EDM Die-Sinking (Plunge),Advanced Manufacturing Technology,The spark discharges are pulsed on and off at a high frequency cycle and can repeat 250,000 times per second. Each discharge melts or vaporizes a small area of the workpiece surface.,During normal operation the electrode never touches the workpiece, but is separated by a small spark gap.,The amount of material removed from the workpiece with each pulse is directly proportional to the energy it contains.,The electrode (plunger) can be a complex shape, and can be moved in X, Y, and Z axes, as well as rotated, enabling more complex shapes with accuracy better than one mil.,Plunge EDM is best used in tool and die manufacturing, or creating extremely accurate molds for injection-molding plastic parts.,Electrical Discharge Machining（EDM）,Advanced Manufacturing Technology,A relatively soft graphite or metallic electrode can easily machine hardened tool steels or tungsten carbide. One of the many attractive benefits of using the EDM process.,The dielectric fluid performs the following functions: It acts as an insulator until sufficiently high potential is reached . Acts as a coolant medium and reduces the extremely high temp. in the arc gap. More importantly, the dielectric fluid is pumped through the arc gap to flush away the eroded particles between the workpiece and the electrode which is critical to high metal removal rates and good machining conditions.,Electrical Discharge Machining（EDM）,Advanced Manufacturing Technology,The EDM process can be used on any material that is an electrical conductor,Applications include producing die cavity for large components, deep small holes, complicated internal cavities,Dimensional accuracy of 0.0005 in is achievable.,Minimum wall thickness: .01 inch, over 5 inch span,Feature to feature positioning: .001,The EDM process does not involve mechanical energy, therefore, materials with high hardness and strength can easily be machined.,Wire edm,Advanced Manufacturing Technology,Wire EDM machines utilize a very thin wire (.0008 to .012 in.) as an electrode. The wire is stretched between diamond guides and carbide that conduct current to the wire and cuts the part like a band saw. Material is removed by the erosion caused by a spark that mo