INTRODUCTION OF ELECTRIC DISCHARGE MACHINING (EDM)
Electric discharge machining (EDM) is a manufacturing process whereby a wanted shape of an object of workpiece is obtained using electrical discharges (sparks). The material removal from the workpiece occurs by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. Introduction of EDM Die Sinking Machine EDM die sinking machine consists of an electrode and workpiece that are submerged in an insulating liquid such oil or, less frequently, other dielectric fluids. The electrode and workpiece are connected to a suitable power supply. As the electrode approaches the workpiece, dielectric breakdown occurs in the fluid forming a plasma channel and a small spark jumps. These sparks usually strike one at a time because it is very unlikely that different locations in the inter-electrode space have the very identical local electrical charachetistics which would enable a spark to occur simultaneously in all such locations. The EDM die sinking process is most widely used by the mould-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. Brand from YIHAWJET ENTERPRISES CO.
Example branded from YIHAWJET ENTERPRISES CO.
TOOLS FOR EDM DIE SINKER
EDM DIE SINKER COMPONENT
Power Supply The power supply controls the electrical discharges and movement of the electrode in relation to the workpiece
2. MACHINING 3 AXIS : X, Y, Z
ELEVATING WORK TANK
FLUID DIE ELECTRIC The Method Die electric fluid o The border area sparking from oxsigen. o Produce to help sparking area electrode and workpiece. o As coolant fluid o Function to outside dust metal from workpiece. The type of Fluid Die Electric o Light lubricant oil o Transformer oil o Silicon – base oil o Corbon tetrachloride o Kerosene
ELECTRODE The Character electrode specimen o The low erosion o The good eklectrical flow. o The high efficiency to dismiss high carbon steel. The electrode specimen o Copper o Copper tungsten o Graphite
OPERATION OF ELECTRICAL DISCHARGE MACHINE (EDM)
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)
• During normal operation the electrode never touches the workpiece, but is separated by a small spark gap. • 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. • 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. • The amount of material removed from the workpiece with each pulse is directly proportional to the energy it contains. • Plunge EDM is best used in tool and die manufacturing, or creating extremely accurate molds for injection-molding plastic parts.
• 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. • 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 PROGRAM OF EDM DIE SINKER
CODE COMMAND o Machining o G100 – Single Machining for rough process o G101 – Bottom stopped simple o G103 – Through machining o G104 – Corner machining o Positioning G110 – Point G111 – Line / grid (setting m/c positions on line/grid) G112 – Arc/circumference G113 – Dispersed (setting dispersed position) G114 – Plural Coordinate (setting m/c positions in plural cord systems) G115 – Split positioning (repeated positioning in each m/c process) o Measuring G120 – Edge face (positioning to edge process) G121 – Groove/hole (positioning center of groove/hole) G122 – Plate/column (positioning center of plate/column) G124 – Center Holes (positioning to center plural holes) G125 – Measure/sphere (positioning spindle ball/table) G126 – Electrode/sphere (positioning electrode/sphere ball) o Auxiliary G131 – Automatic tool changer G133 – G function processing G134 – M function processing
FLUIDS IN EDM DIE SINKER
As mentioned the dielectric fluid acts as an insulator between the electrode and the mold cavity. There are many dielectrics to choose from based on the insulation properties of the fluid. Air is not a very good insulator. Water is best. But water has a few drawbacks. First, it causes rust. Second, the electrical discharge separates the water into pure hydrogen and pure oxygen. A very explosive pair. A good compromise then is kerosene. No rust problem and no dangerous gasses are produced with kerosene.
The dielectric must be constantly filtered, cooled and recirculated. A great deal of heat is generated during the EDM process and the dielectric absorbs the most of it. Additionally the process creates a lot of debris and this needs to be filtered out of the system.
The type of Fluid Die Electric o Light lubricant oil o Transformer oil o Silicon – base oil o Corbon tetrachloride o Kerosene
THEORY OF ELECTRODE IN EDM DIE SINKER
An electrode is a conductor through which electric current is passed. Found in variable forms, electrodes may be wires, plates, or rods. An electrode may be constructed of metal, such as copper, silver, lead, or zinc. However, an electrode may also be made of a nonmetal substance, such as carbon. An electrode passes current between a metallic part and a nonmetallic part of an electrical circuit. Most frequently, conductors that are metallic carry electrical current. In other circuits, however, current is passed through a nonmetallic conductor. In an electrochemical cell, an electrode is called either an anode or a cathode. An anode is an electrode at which current leaves the cell and oxidation takes place. For example, an anode is the positive electrode in a storage battery. A cathode is described as a negative electrode. Current enters the cell at the cathode and reduction takes place. Electrons are repelled from the cathode. When it comes to certain electric devices, like electric batteries, the anode may actually be negative and the cathode may be positive. In such cases, a conversion of non-electric energy to electric energy occurs and current flows from the negative electrode to the positive electrode. However, most familiar electronic devices involve current that flows from the positive electrode or anode to the negative electrode or cathode.
TYPES OF ELECTRODES 1. Copper
2. Copper tungsten
3. Graphite
4. Brass
EXAMPLE PRODUCTS MADE FROM EDM
CONCLUSION 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)
