The Electrical Discharge Machining process, known as spark machining or arc machining, is conceptually very simple: an electric current passes between an electrode and a workpiece separated by a dielectric liquid.
The dielectric liquid acts as an electrical insulator until sufficient voltage is applied to bring it to its ionization point, after which it becomes electrically conductive. The resulting spark discharge erodes the workpiece into its final shape.
An EDM machine has long been the solution for high-precision machining applications where conventional metal removal methods are impractical, complex, or impossible.
What exactly is EDM?
Electrical discharge machining (EDM) has long been the answer for demanding, high-precision machining applications where conventional metal removal is difficult or impossible.
Known by many other names, such as spark machining, arc machining, and (inaccurately) flaring, the EDM process is conceptually very simple: an electric current passes between an electrode and a workpiece separated by a dielectric liquid.
The dielectric liquid acts as an electrical insulator unless sufficient voltage is applied to bring it to its ionization point, at which point it becomes an electrical conductor.
The resulting spark discharge erodes the part to give it the desired final shape. Like processes such as laser cutting, EDM does not require mechanical force in the removal process.
How does EDM work?
It consists of placing an electrode or wire and an electrically conductive part in a circulating dielectric fluid. It is a non-contact process that can machine parts regardless of their hardness.
The fluid acts as an insulator until a specific spark gap and voltage ionize it and allow a spark of approximately 8,000 and 12,000 ºC, high enough to erode part of the part.
Using a CNC, the operator moves the electrode or wire as needed and quickly turns the current on and off. In this way, can clean molten material (often referred to as “swarf”) from the part. The ratio of the on-time to the off time is called the “duty cycle” of the EDM process.
There are three primary variants of the EDM process: sinking EDM (also called “ram” or “vertical” EDM), hole drilling EDM, and wire EDM. Each uses different materials and is suited to various end applications.
Different types of EDM
Wire EDM
The basic principle of operation is to use a thin, continuously moving metal wire (called an electrode wire) as an electrode to perform a pulsed spark discharge on the workpiece to remove the metal and cut the shape.
This non-traditional processing technology uses electricity to take a thin charged copper or brass wire as an electrode to cut any conductive material with precision and accuracy.
Wire EDM is a metal machining process in which a tool discharges thousands of sparks into a metal part. Instead of cutting the material, EDM melts or vaporizes it, leaving tiny debris and providing an exact line.
Wire EDM requires a hole in the metal through which to pass the wire to melt the surrounding material. This technique uses a single wire that can vary in size and material.
This process uses a moving wire electrode (typically 0.010″ diameter or smaller) that passes through the part. The wire, in this case, is computer-controlled, following the geometry assigned for the part to be produced.
EDM is very popular in tool and mold making because of its applicability, especially for hard materials such as titanium or for particularly complex shapes that are difficult to achieve with milling.
Sinker EDM
Sinking EDM, also known as ram EDM, conventional EDM, die sinking, or cavity-type EDM, uses machined electrodes of different shapes, sizes, and materials to remove material from the workpiece.
This process uses pre-machined copper or graphite electrodes to form a “positive” of the required shape. The electrode is usually graphite, but copper, tungsten, or brass and combinations of these materials can also be used. To achieve the necessary specifications, we can customize the geometric characteristics of the electrode.
Many factors can influence the choice of electrode material in sinking EDM. These include the electrode’s resistance to erosion and its conductivity, which is usually easier to machine than copper material. However, copper is more resistant and conducive.
The electrode is then pressed into the part to create a negative of the material’s original shape. Next, both the part and the electrode are immersed in an insulating fluid of oil or synthetic oil. Finally, the machine automatically uses CNC technology to direct the electrode to the part.
As in wire EDM, when the electrode approaches the part, the force of the charge breaks the dielectric fluid barrier and generates a spark, which erodes a small amount of material by melting and vaporizing small particles.
This process is repeated hundreds of thousands of times per second. While removing material, the machine continues to control the movement of the electrode until it reaches the desired size.
Intricate angles, deep cuts, and custom shapes that a typical CNC machine (vertical or horizontal milling machine, 3-axis, 4-axis, or 5-axis CNC machines) cannot achieve can be done with a sinking EDM.
Hole drilling by EDM
EDM hole drilling works on the same technical principles as wire EDM. However, EDM hole drilling uses an electrically charged metal electrode tool that functions much like a traditional drill bit for machining holes instead of wire.
This machine uses a rotating conductive tube for its electrode and a continuous dielectric fluid flow (usually deionized water) to clean the cut. Even in hardened or exotic materials, creating accurate and precise holes has been a critical development for several advanced technologies, such as the cooling holes created by EDM in high-temperature alloy turbine blade sections.
This enables a “film cooling” process, allowing jet engines to operate at higher temperatures for excellent durability and efficiency.
Small hole EDM is ideal for parts requiring starter holes, vent holes, coolant holes, thimble holes, or other blind holes and is very useful for removing broken taps and bits.
Small-hole EDM uses hollow circular electrodes to drill holes in the part. Even in hardened or heterogeneous materials, accurate and precise holes can be created, which has become a critical development in several advanced technologies.
Electrical Discharge Machining in Northridge, CA
Electrical discharge machining was invented in the 1940s and is a very early non-traditional process. However, combined with computer numerical control (CNC), it has become an accurate and reliable machining method and has now become the standard for more conventional cutting methods.
Electrical discharge machining remains the answer to the most demanding machining applications. It helps engineers reshape materials where traditional methods are difficult or impossible. In addition, this unique process contributes to the creation of high-quality components.
At Maroney Company, our EDM processes are the perfect solution for your manufacturing needs. This process allows us to create high-precision cuts and works well with any conductive material. As a result, we can better serve you, regardless of your part requirements and applications.
We have customers who have projects that need to fabricate strong metals, some seamless and used in high-pressure industrial work. These parts must be solid and precise. Our team can adapt to these needs with EDM.
Our team at Maroney Company has over 60 years of experience in precision machining and holds AS9001AD and ISO 9001:2015 certifications and DDTC (ITAR) 2022 registration. Our professionals have seen it all with training and years of experience handling and engineering precision complex parts for petroleum, aerospace, energy, and even prototyping.
If you’re looking for an accurate, precise, and stress-free machining process, at least on the part, EDM could be just what you need. And at Maroney Company, with the help of our fully programmable 4-axis EDM equipment, we can produce more significant components with more incredible speed and accuracy and a greater degree of economy and flexibility for all your needs. Visit our list of services we offer for you.
Contact us for your Electrical Discharge Machining requirements
At Maroney Company, we look forward to helping our customers with their requirements pertaining to electrical discharge machining. Please give us a call at (818) 882-2722 or contact us to discuss your needs and find custom solutions tailored just for you.