27-06-2014, 10:07 AM
PRESENTATION ON WIRE EDM
[attachment=65391]
Electrical discharge machining
Electric discharge machining (EDM), sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks).
Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the ‘tool’ or ‘electrode’, while the other is called the workpiece-electrode, or ‘workpiece’.
HISTORY
The beginning of EDM came during the Second World
War, when two Russian physicists B.R. and N.I. Lazarenko published their study on The Inversion of the Electric Discharge Wear Effect. which related to the application to manufacturing technology of the capacity of electrical discharges, under controlled distribution, to remove metal.
EDM was being used at that time to remove broken taps and drills. The early “Tap- Busters” disintegrated taps with hand fed electrodes, burning a hole in the center of the tap or drill, leaving the remaining fragments that could be picked out. This saved workpieces and very expensive parts from being scrapped and having to be made over again.
WIRE EDM
Wire EDM (Vertical EDM's kid brother), is not the new kid on the block. It was introduced in the late 1960s', and has revolutionized the tool and die, mold, and metalworking industries. It is probably the most exciting and diversified machine tool developed for this industry in the last fifty years, and has numerous advantages to offer.
It can machine anything that is electrically conductive regardless of the hardness, from relatively common materials such as tool steel, aluminum, copper, and graphite, to exotic space-age alloys including hastaloy, waspaloy, inconel, titanium, carbide, polycrystalline diamond compacts and conductive ceramics.
MACHINE
Wire EDM’s are manufactured in various sizes and styles of flush or submerged type machines to fit the needs of the consumer. Large scale EDM’s can handle workpieces weighing over ten thousand pounds and can cut over twenty inches thick. Automatic Wire Threaders (AWT) are usually standard equipment on most models. In addition to the X-Y table travels, wire EDM’s have U / V travels for providing the movement to cut tapers. Most machines can cut tapers of 20-30 degrees depending on workpiece thickness.
PRINCIPLE OF WIRE ELECTRICAL DISCHARGE MACHINING
The Spark Theory on a wire EDM is basically the same as that of the vertical EDM process. In wire EDM, the conductive materials are machined with a series of electrical discharges (sparks) that are produced between an accurately positioned moving wire (the electrode) and the workpiece.
High frequency pulses of alternating or direct current is discharged from the wire to the workpiece with a very small spark gap through an insulated dielectric fluid (water).
COMPUTER NUMERICAL CONTROL (CNC)
Today’s numerical control is produced with the needs of the operator in mind. Programs, machine coordinates, cutting speeds, graphics and relevant information is displayed on a color monitor, with easy to use menu’s.
The numerical control offers the capabilities of scaling, mirror imaging, rotation, axis exchange and assist programs. This enables an operator to produce an entire family of parts from a single program without the need to edit the program.
Power Supply
When wire EDM machines were first introduced in the United States, they were equipped with power supplies that could achieve less than one square inch per hour.
Today, most machines are rated to cut over twenty square inches per hour and faster. Faster or slower speeds are obtained depending on the workpiece material, part thickness, wire diameter, type of wire, nozzle position, flushing condition and required part accuracy. .
MECHANICAL SECTION
Table movement
Machine movement is accomplished with precision lead screws with recirculating ball bearings on all axes that are driven by AC motors. Before shipping, the machine’s position is checked and any errors or backlash are corrected by pitch error compensation that is permanently stored in the computers memory.
DIELECTRIC SYSTEM
Wire EDM uses deionized water as the dielectric compared to Vertical EDM’s that use oil. The dielectric system includes the water reservoir, filtration system, deionization system, and water chiller unit.
During cutting, the dirty water is drained into the unfiltered side of the dielectric reservoir where the water is then pumped and filtered through a paper filter, and returned to the clean side of the dielectric tank.
Submerged Machining
Submerged machining is extremely useful for applications that generally have poor flushing conditions. Some applications and examples where submerged machining is more practical would be cutting large taper angles, tall workpieces, laminations, tubes, irregular shaped parts, workpieces with undercuts and cutting very close to the edge of the workpiece.
[attachment=65391]
Electrical discharge machining
Electric discharge machining (EDM), sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges (sparks).
Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the ‘tool’ or ‘electrode’, while the other is called the workpiece-electrode, or ‘workpiece’.
HISTORY
The beginning of EDM came during the Second World
War, when two Russian physicists B.R. and N.I. Lazarenko published their study on The Inversion of the Electric Discharge Wear Effect. which related to the application to manufacturing technology of the capacity of electrical discharges, under controlled distribution, to remove metal.
EDM was being used at that time to remove broken taps and drills. The early “Tap- Busters” disintegrated taps with hand fed electrodes, burning a hole in the center of the tap or drill, leaving the remaining fragments that could be picked out. This saved workpieces and very expensive parts from being scrapped and having to be made over again.
WIRE EDM
Wire EDM (Vertical EDM's kid brother), is not the new kid on the block. It was introduced in the late 1960s', and has revolutionized the tool and die, mold, and metalworking industries. It is probably the most exciting and diversified machine tool developed for this industry in the last fifty years, and has numerous advantages to offer.
It can machine anything that is electrically conductive regardless of the hardness, from relatively common materials such as tool steel, aluminum, copper, and graphite, to exotic space-age alloys including hastaloy, waspaloy, inconel, titanium, carbide, polycrystalline diamond compacts and conductive ceramics.
MACHINE
Wire EDM’s are manufactured in various sizes and styles of flush or submerged type machines to fit the needs of the consumer. Large scale EDM’s can handle workpieces weighing over ten thousand pounds and can cut over twenty inches thick. Automatic Wire Threaders (AWT) are usually standard equipment on most models. In addition to the X-Y table travels, wire EDM’s have U / V travels for providing the movement to cut tapers. Most machines can cut tapers of 20-30 degrees depending on workpiece thickness.
PRINCIPLE OF WIRE ELECTRICAL DISCHARGE MACHINING
The Spark Theory on a wire EDM is basically the same as that of the vertical EDM process. In wire EDM, the conductive materials are machined with a series of electrical discharges (sparks) that are produced between an accurately positioned moving wire (the electrode) and the workpiece.
High frequency pulses of alternating or direct current is discharged from the wire to the workpiece with a very small spark gap through an insulated dielectric fluid (water).
COMPUTER NUMERICAL CONTROL (CNC)
Today’s numerical control is produced with the needs of the operator in mind. Programs, machine coordinates, cutting speeds, graphics and relevant information is displayed on a color monitor, with easy to use menu’s.
The numerical control offers the capabilities of scaling, mirror imaging, rotation, axis exchange and assist programs. This enables an operator to produce an entire family of parts from a single program without the need to edit the program.
Power Supply
When wire EDM machines were first introduced in the United States, they were equipped with power supplies that could achieve less than one square inch per hour.
Today, most machines are rated to cut over twenty square inches per hour and faster. Faster or slower speeds are obtained depending on the workpiece material, part thickness, wire diameter, type of wire, nozzle position, flushing condition and required part accuracy. .
MECHANICAL SECTION
Table movement
Machine movement is accomplished with precision lead screws with recirculating ball bearings on all axes that are driven by AC motors. Before shipping, the machine’s position is checked and any errors or backlash are corrected by pitch error compensation that is permanently stored in the computers memory.
DIELECTRIC SYSTEM
Wire EDM uses deionized water as the dielectric compared to Vertical EDM’s that use oil. The dielectric system includes the water reservoir, filtration system, deionization system, and water chiller unit.
During cutting, the dirty water is drained into the unfiltered side of the dielectric reservoir where the water is then pumped and filtered through a paper filter, and returned to the clean side of the dielectric tank.
Submerged Machining
Submerged machining is extremely useful for applications that generally have poor flushing conditions. Some applications and examples where submerged machining is more practical would be cutting large taper angles, tall workpieces, laminations, tubes, irregular shaped parts, workpieces with undercuts and cutting very close to the edge of the workpiece.