Electrical discharge machining, or EDM for short, is a highly accurate machining process that is popular for use in applications that require the creation of intricate details or complex geometries. EDM is also used in the production of dies for casting and forging, plastic molds, compressor blades, and other engine parts and a myriad of applications in the worlds of aerospace, automotives, defense, extrusion, electronics, food and beverage, medicine, and stamping.
The method of electrical discharge machining uses electrical energy to etch, drill, machine, and cut metal parts. It also frequently employs CNC EDM machines to carefully manage the process, allowing for incredibly precise results on both extremely delicate or breakable materials and hard metals that do not respond well to other machining processes, such as hardened steel, titanium alloys, and nickel-based superalloys.
EDM tools generally consist of an electrode, wire, or shaped tool and a power source to which it is connected. This power source helps it create electrical discharge, or sparks, which can produce high heat anywhere between eight and twenty thousand degrees. Unlike many other machining methods, EDM does not use impact or abrasion to achieve its goals.
In fact, the EDM tool never makes physical contact with the part being machined, and because of this, the part being worked on is not deformed, nor does it sustain heat damage or imperfections like burrs. Rather, using electrical discharges, the EDM tool establishes a conductive path or arc between itself and the workpiece, generating an intense electrical field between them. This generated electrical field then erodes the surface of the workpiece in a predetermined pattern or shape.
This is why EDM is also sometimes called spark eroding, spark machining, or die sinking. All of this activity goes on while the EDM tool and workpiece are immersed in a water-based dielectric fluid bath. The bath helps by conducting electricity between the workpiece and the EDM tool (more quickly wearing away unwanted material), flushing away debris, and preventing premature sparking.Read More…
From here, the EDM process becomes more individualized; there are a variety of EDM methods that manufacturers can employ to suit their needs. Methods include: conventional EDM, wire EDM, small hole EDM, and micro EDM.
Conventional EDM, also known as ram EDM, sinker EDM, or plunge EDM, is the oldest and of one of the two most widely used forms of electrical discharge machining. This method uses an electrode, which is most often made out of machined graphite, though it may also be copper, that plunges, or sinks, into metal to create complex 3D shapes, holes, and patterns.
Wire EDM, sometimes called wire erosion, is the other main type of electrical discharge machining. Instead of using an electrode, wire EDM uses a wire to transmit sparks to the workpiece. This wire, which is made of brass, is fed from a spool through the workpiece and then clamped on both ends by CNC-controlled diamond guides. To create shapes and patterns, the wire cuts through the metal in a pattern that is based on the movement of the arms of the CNC-operated guides. In order for wire EDM to take place, the part being cut must first undergo the next process, small hole EDM.
Small hole EDM is a method of EDM drilling that creates holes and perforations. So, it is used before wire EDM to create a hole through which the wire can be fed.
Finally, micro EDM is a process that treats extreme precision parts. Also known as μ EDM, micro EDM create erosions in nanoscale dimensions, and allows for the cutting and tooling of parts that could not receive accurate treatment.
Each EDM process is well-suited for one task or another. Sinker EDM, for example, is the best process to employ for the creation of complex geometries. Wire EDM, on the other hand, which can be quite efficient, works well for cutting shapes into both selected parts and entire assemblies. Micro EDM processes work well for sensitive medical tools, optical tools, apertures, and the like. No matter the EDM process chosen, most electrical discharge machining equipment is guided, controlled, or monitored by CNC machines or CAM/CAD software.
EDM machines can cut through most any metal. Examples of materials they work with include: aluminum, bronze, cobalt, copper, bronze, gold, lead, nickel, silicon, stainless steel, titanium, and tungsten. In addition, all EDM machines can accurately cut these materials, including even the hardest of metals, without the necessity of preheating them. The removal of this step in the machining process saves manufacturers both time and money.
When deciding on what tool or tools are best for their application, manufacturers should consider variables such as shape and size, as well as the material of the workpiece, which must match with the material of the electrode or tool in order to work properly.