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Electrical discharge machining (EDM), also known as spark machining, die cutting, wire burning, or wire erosion, is a metal fabrication process that uses an electric field generation reaction to produce the desired shape. This type of machining causes the material to be removed from an object by a series of rapidly repeating electrical discharges between two electrodes separated by a dielectric fluid and subjected to a voltage. One electrode is called the tool electrode, or simply the tool or electrode, while the other is called the workpiece electrode. The process depends on the tool and workpiece being in physical contact. As the voltage between the two electrodes increases, the electric field strength in the volume between the electrodes becomes more excellent, causing the dielectric breakdown of the liquid and the generation of an arc. As a result, the material is removed from the electrodes. When the current is stopped, the new liquid dielectric is transferred to the inter-electrode volume, thus eliminating solid particles (waste) and restoring the insulating properties of the dielectric. Adding new liquid dielectric to the interelectrode volume is commonly called flushing. After the current flows through the carbides or any other element, the voltage between the electrodes returns to the state before the flashover so that the liquid dielectric can be flashover again to repeat the cycle. What is EDM machining? How does wire EDM work? Read about it below!

Wire electrical discharge machining processes

Electrical Discharge Machining process (EDM), also known as Spark Machining or Spark Erosion, is a manufacturing process that uses an electrical discharge (spark) to produce desired parts from sheet metal. There are three types of EDM:

– EDM,

– Wire-cut EDM

– EDM for high-speed drilling.

Wire EDM, also known as WEDM, involves the use of thin single-strand conductive metal wire (such as brass) and deionized water, which allows the use of wire derived from EDM.

How do wire EDM process?

In wire wire edm machine, the material is removed from the workpiece by a series of rapidly repeated electrical discharges between the wire or electrode and the workpiece, separated by dielectric fluid. Wire EDMs can easily cut hard conductive materials and produce complex parts with high precision. Dielectrics are used to prevent short circuits in spark and waste disposal processes.

What is wire EDM used for?

Wire EDM machines are a metalworking process that will prove to be an excellent choice for producing small precision parts. It can also be used in many other applications, including automotive, aerospace, electronics, and other industries, among others:

– Mold making,

– complex equipment and tools,

– Rapid prototyping and total production,

– Applications requiring low levels of residual stress,

– Small and detailed parts,

– drilling small holes,

– metal decay repair,

– circular manufacturing.

Wire EDM (Electric Discharge Machining)

WEDM wire machining, also known as Wire EDM, is a thin single-stranded metal wire (usually brass) fed into a bath of an artifact of dielectric fluid (usually deionized water). The EDM wire uses the EDM process to cut sheet metal up to 300 mm thick and make hard metal punches, tools, and dies that are otherwise difficult to machine. The wire, which is continuously fed from a spool, is held between an upper and lower diamond guide located in the middle of the waterjet head. The guide, usually CNC-controlled, moves along the x-y axis of the plane. On most machines, the top slider can also move independently along the z-u-v axis, allowing the cutting of cones and transitions (e.g., circles at the bottom and squares at the top). The top slider can control the movement of the axes in the G-Code standard, x-y-u-v-i-j-k-l. This allows wire cutters to be programmed to cut very complex and delicate shapes. The accuracy of the top and bottom diamond guide is typically 0.004 mm (0.16 mils) and can have a cutting path or clearance as small as 0.021 mm (0.83 mils) using 0.02 mm (0.79 mils) wire, despite the average cut provided. The best cost and machining time using 0.25 mm (9.8 mils) brass wire is 0.335 mm (13.2 mils).

Prototype manufacturing

The EDM process is most commonly used in the molding, tool, and die industry. Still, it is becoming a common prototype and part production method, especially in the relatively low-volume aerospace, automotive, and electronics industries. In an EDM rod, graphite, tungsten copper, or pure copper electrodes are machined into the desired (negative) shape and inserted into the workpiece at the end of a vertical slide.

Manufacturing coin dies

For making jewelers’ dies and stamps, or for punching and perforating (using pancake punches) when striking coins (stamping), the obverse pattern can be made from sterling silver since (with the right machine settings) the pattern is heavily zeroded and is used only once. The resulting harmful mold is then hardened and used in drop hammers to produce stamped flat steel from bronze billets, silver, or low-resistance gold alloys. These flat surfaces can be further formed into curved surfaces using another mold for badges. This type of EDM is usually done in oil-based immersion dielectrics. The finished product can be further refined with hard enamel (glass), soft enamel (paint), or galvanized with pure gold or nickel. More delicate materials, such as silver, can be hand-carved as an enhancement.

Drilling small holes

Wire EDM drilling is used for many things. In a wire EDM, small-hole drilling is used to drill a hole in the workpiece that the wire must pass through to perform a wire EDM operation. A separate EDM head explicitly designed for small-hole drilling is mounted on the wire EDM, allowing finished parts of large hardened plates to be etched on demand without pre-drilling. The EDM for small holes is used to drill the leading and trailing edges of turbine blades used in jet engines. The airflow through these tiny holes allows the engine to operate at higher temperatures than it would otherwise. The high-temperature, tough monocrystalline alloys used in these blades make routine machining these high aspect ratio holes difficult, sometimes even impossible. Electric erosion phenomena with small holes can also be used to create micro-holes for fuel system components, spinning nozzles for manufactured fibers such as artificial silk, and many other applications.

There are also stand-alone EDM machines for drilling small holes in the x-y axis, also known as super drills or drill bits, which can machine blind or through holes. The EDM uses a long brass or copper tube electrode that rotates in a chuck with a constant flow of distilled or deionized water through the electrode as a flushing agent and dielectric. The electrode tube behaves like a wire in a wire EDM, with sparking and wear rates. Some EDMs with small holes can drill 100 mm of mild or hardened steel in less than 10 seconds with an average wear rate of 50% to 80%. With this drilling operation, holes from 0.3 mm to 6.1 mm can be made. Brass electrodes are easier to work with but are not recommended for wire-cutting procedures because corrosion from brass particles can cause brass-on-brass wire breakage, so copper is recommended.

Advantages and disadvantages of EDM

EDM ensures that machining precision is maintained and that complex parts can be machined. The process is often compared to electrochemical machining. The advantages of EDM are:

– the ability to machine complex shapes that would otherwise be difficult to produce with conventional cutting tools;

– The ability to machine tough materials with very tight tolerances;

– the ability to machine minimal parts, whereas conventional cutting tools can damage parts due to excessive cutting tool pressure;

– The lack of direct contact between the tool and the workpiece. As a result, delicate parts and fragile materials can be handled without noticeable deformation;

– provides a good surface finish, which can be achieved with redundant finishing paths.

– The ability to produce magnificent holes;

– making tapered holes;

– internal profile and internal corners of tubes or vessels down to 0.001 inches.

Disadvantages of EDM include:

– difficulty in finding professional operators,

– slow material removal;

– potential fire hazards associated with the use of fuel oil-based dielectrics;

– additional time and cost associated with creating EDM plunger/sedimentation electrodes;

– due to electrode wear, makes it challenging to reproduce sharp corners on the workpiece;

– specific power consumption, which is very high;

– high power consumption;

– performance of „cutting”;

– excessive tool wear during machining;

– non-conductive materials can only be processed using specific process configurations.

 EDM makes the need to process parts much more precise. The applicability of EDM is based on having the right equipment and operator.