EDM refers to wire electrical discharge machining. Wire electrical discharge machining or EDM is a metalworking process with the help of which a material is separated from a conductive work piece, by means of electrical erosion.
The wire never comes in contact with the conductive work piece. The wire electrode leaves a path on the work piece, which is slightly larger than the wire. Most often a 0.010′ wire is used which creates a 0.013′ to 0.014′ gap. The wire electrode once passed through the work piece cannot be reused.
Wire electrical discharge machining is mainly used to cut intricate shapes and designs into hard metals, which are otherwise difficult to form, mold or manipulate. It is most useful in the electronics and aerospace sectors for prototyping and manufacturing various parts. Most often, steel and titanium are processed with help of wire electrical-discharge machining. Jewelry designers are using the system for cutting intricate shapes. Even artists working with metals find the machining very convenient and practical to use.
Many manufactures are profiting from the production of wire electrical discharge machining systems. There is a large selection available in EDM wires, providing a choice of optimum brands, typed, diameter, spool size and spool weight for almost any machine and application.
What Is Wire EDM?
Wire electrical discharge machining is a non-contact subtractive manufacturing process that uses an electrically charged thin wire with a dielectric fluid to cut a metal part into different shapes.
The process produces small chips and precise cut lines by melting or vaporizing the material rather than cutting it. As a result, it can conveniently machine parts unsuitable for conventional machining techniques. However, the parts must be electrically conductive.
How Does Wire EDM Work?
Machining a part using the process involves submerging the workpiece into a dielectric fluid, securing it with a machinist vise, and running the wire through it to produce sparks as it passes an electric current.
In other words, the wire carries one side of the charge, and the workpiece, which must be a conductive material, carries the other side of the charge. When the two get close, a hot electric charge jumps the gap and melts tiny pieces of the metal away.
The electric spark is the cutting tool to cut the material in the desired shape. Additionally, the wire EDM process involves deionized water to control the process and flush away tiny particles removed
The electrical discharge machining (EDM) process as we know it today started with the observations of Joseph Preistly in 1770. He noticed that electrical discharges had removed material from the electrodes in his experiments. This is also known as electro-discharge erosion.
In the 1940s two Soviet researchers, the Lazarenkos, developed a machining process that formed the foundation for modern wire EDM and small hole EDM. Practical electrical discharge machines were eventually developed, using more powerful pulse generators, automatic repeated discharge and steady dielectric fluid flow to control the process.
EDM is also known as: spark machining, spark eroding, and die sinking.
Wire EDM is also known as: wire-cut EDM, wire cutting, EDN cutting, EDM wire cutting, wire burning, wire erosion, wire eroding, wire cut electric discharge machining, and ‘cheese-cutter’ EDM.
Wire electrical discharge machining (WEDM) uses a metallic wire to cut or shape a workpiece, often a conductive material, with a thin electrode wire that follows a precisely programmed path. Typically the electrode diameters range from .004″ – .012″ (.10mm – .30mm), although smaller and larger diameters are available.
During the wire cutting process there is no direct contact between the wire and the workpiece which allows for machining without causing any distortion in the path of the wire, or the shape of the material. To accomplish this, the wire is very rapidly charged to a desired voltage. The wire is also surrounded by deionized water. When the voltage reaches the correct level, a spark jumps the gap and melts a small portion of the work piece. The deionized water cools and flushes away the small particles from the gap.
The hardness of the work piece material has no detrimental effect on the cutting speed. Extrusion dies and blanking punches are very often machined by wire cutting.
EDM cutting is always through the entire workpiece. To start wire machining it is first necessary to drill a hole in the workpiece or start from the edge. On the machining area, each discharge creates a crater in the workpiece and an impact on the tool. The wire can be inclined, thus making it possible to make parts with taper or with different profiles at the top and bottom. There is never any mechanical contact between the electrode and workpiece (see above). The wire is usually made of brass or stratified copper, and is between 0.1 and 0.3 mm diameter.
Depending on the accuracy and surface finish needed, a part will either be one cut or it will be roughed and skimmed. On a one cut the wire ideally passes through a solid part and drops a slug or scrap piece when it is done. This will give adequate accuracy for some jobs, but most of the time, skimming is necessary.
What types of shapes can a wire EDM machine produce?
A wire EDM machine is a type of CNC machine that can move along four independent axes to generate taper cuts. For example, a stamping die can be machined with 1/4 degree taper or a mold with one degree taper in some areas and two degrees in another with precision. Extrusion dies or nozzles and horns can be cut with constantly changing tapers. For example, a detailed shape on the top of the work piece can transition to a simple circle on the bottom.
Uses for EDM Cutting
Our wire cut EDM services are ideal for delicate or small work pieces that may be damaged during conventional machining or other traditional techniques:
Thick parts requiring good finishes and/or accuracies.
Complex shapes or narrow slots
Larger parts that need to hold accurate tolerances
Delicate, hard, exotic/expensive or weak materials
Wire EDM is also known as: wire-cut EDM, wire cutting, EDN cutting, EDM wire cutting, wire burning, wire erosion, wire eroding, wire cut electric discharge machining, and ‘cheese-cutter’ EDM.
Wire electrical discharge machining (WEDM) uses a metallic wire to cut or shape a workpiece, often a conductive material, with a thin electrode wire that follows a precisely programmed path. Typically the electrode diameters range from .004″ – .012″ (.10mm – .30mm), although smaller and larger diameters are available.
During the wire cutting process there is no direct contact between the wire and the workpiece which allows for machining without causing any distortion in the path of the wire, or the shape of the material. To accomplish this, the wire is very rapidly charged to a desired voltage. The wire is also surrounded by deionized water. When the voltage reaches the correct level, a spark jumps the gap and melts a small portion of the work piece. The deionized water cools and flushes away the small particles from the gap.
The hardness of the work piece material has no detrimental effect on the cutting speed. Extrusion dies and blanking punches are very often machined by wire cutting.
A wire EDM machine is a type of CNC machine that can move along four independent axes to generate taper cuts. For example, a stamping die can be machined with 1/4 degree taper or a mold with one degree taper in some areas and two degrees in another with precision. Extrusion dies or nozzles and horns can be cut with constantly changing tapers.
A skim cut is where the wire is passed back over the roughed surface again with a lower power setting and low pressure flush. There can be from one to nine skim passes depending on the accuracy and surface finish required. Usually there are just two skim passes. A skim pass can remove as much as 0.002″ of material or a as little as 0.0001″. During roughing ( i.e. the first cut) the water is forced into the cut at high pressure in order to provide plenty of cooling and eliminate eroded particles as fast as possible. During skimming (accuracy / finish cuts) the water is gently flowed over the burn so as not to deflect the wire.
Our wire cut EDM services are ideal for delicate or small work pieces that may be damaged during conventional machining or other traditional techniques:
Thick parts requiring good finishes and/or accuracies.
Complex shapes or narrow slots
Larger parts that need to hold accurate tolerances
Delicate, hard, exotic/expensive or weak materials
EDM cutting is always through the entire workpiece. To start wire machining it is first necessary to drill a hole in the workpiece or start from the edge. On the machining area, each discharge creates a crater in the workpiece and an impact on the tool. The wire can be inclined, thus making it possible to make parts with taper or with different profiles at the top and bottom. There is never any mechanical contact between the electrode and workpiece (see above). The wire is usually made of brass or stratified copper, and is between 0.1 and 0.3 mm diameter.
Depending on the accuracy and surface finish needed, a part will either be one cut or it will be roughed and skimmed. On a one cut the wire ideally passes through a solid part and drops a slug or scrap piece when it is done. This will give adequate accuracy for some jobs, but most of the time, skimming is necessary.
Wire Cut EDM Applications
Because of its versatility, manufacturers use EDM wire cutting machine operation for an extensive range of applications. Because the process can cut very small pieces, it is often an ideal choice for the production of small, highly detailed items that would normally be too delicate for other machining options. Additionally, the process is cost-effective for low quantity projects and can prove to be beneficial in prototype manufacturing, even if the actual project is carried out by different means.
It is important to remember that the wire in the process is constantly moving, and not to be reused. As a result, the copper, brass, or other metallic wire can be miles long, adding cost to the process. And, while the process uses no force and thus does not cause burrs and can be used on delicate items, the possibility of thermal stress is certainly present.
Most machining operations using wire EDM begin with a rough pass with a fairly fast feed rate and high dielectric flow. Successive skim passes take smaller cuts with a reduced dielectric flow to bring finished surfaces into tolerance. The reduced dielectric flow avoids distorting the wire during these skim passes.
Cuts that do not begin along an edge of a part (such as holes) require predrilling to allow the wire to thread through. Many wire EDM machines are fitted with small hole drilling electrodes for this purpose, permitting starting holes to be made in hardened steels without the use of conventional drills. Small hole drills usually employ an EDM electrode mounted in a spinning mandrel with dielectric pumped through the electrode to flush the hole. The process of making small holes in hardened material using standalone EDM drills is sometimes referred to as hole popping.