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Types of EDM Machining (What, Why, When)

EDM uses thermal erosion to remove small bits of conductive metal using repeated electrical discharges between the cutting tool, which functions as the electrode, and the piece itself in the presence of a dielectric fluid. The voltage discharge occurs in the gap between the cutting tool and the piece, and the heat essentially vaporizes small amounts of the metal, which are washed away in a continuous stream of the dielectric fluid. The temperature during EDM processing can reach as high as 15,000 degrees Fahrenheit, and can change the metallurgy of materials. When metallurgical changes occur, the area is referred to as the “recast” layer. The recast layer can be easily removed with various methods.

While all EDM uses an electrical current to cut material, there are several types of EDM that may be used in a specific instance to achieve required results. EDM methods fall into two major categories, wire and ram. Ram/Sinker EDM has several sub-categories of its own. The best EDM method for a part depends on the material and machined shapes required.

Wire EDM

Wire EDM shapes material using a very fine, electrically charged wire which is consumed during the process. All wire EDM machines have a wire drive system to replace the burnt wire automatically as it is consumed so that a fresh wire is always in use. The diameter of the wires typically ranges from .002 to .013 inches, and the resulting cut will be just slightly larger. The wire never actually touches the work, but maintains a gap of at least .001 inches. Output is measured in square inches per hour.

The wire and the piece are flushed with a continuous stream of dielectric fluid, although in some cases they are both completely submerged. With the work piece submerged, you can achieve faster cutting speeds.

The machine configuration affects the complexity of the cuts that can be made with Wire EDM. Four axis machines can make tapered cuts and form parts with different top and bottom configurations. The most flexibility comes with CNC controlled machines, which can perform an extensive range of cuts. All of our machines can cut 4 axis and all are CNC controlled.

Small Hole EDM (Hole Pop EDM)

Small Hole EDM also known as (Hole Pop EDM) uses a cylindrical electrode attached to the positive pole of a pulsed power supply. The work is attached to the negative pole, and the gap between the two is flooded with dielectric fluid. As the electrical pulses remove material, the electrode moves deeper into the work using the path cleared during the EDM process. Using CNC equipment can allow several holes to be drilled sequentially without requiring operator intervention or additional setup. Small Hole EDM is ideal when the part requires starter holes, vent or cooler holes, or any blind holes such as those used for ejector pins.

Ram/Sinker EDM

Ram/Sinker EDM uses electrodes in a wide variety of shapes to create unique cuts. Both the electrode and the piece are submerged in the dielectric fluid during the process. Since the shapes are usually complex, it may require multiple passes. The first passes remove large quantities of material and leave a rough finish while the last pass ensures a smoother surface and exact finish details.

EDM Machining Uses

EDM is ideal for creating tooling, dies or other items made from extremely hard materials and that require wear resistance along with complex shapes. EDM is used widely in automotive and aircraft components. Component sizes can range from very small to moderately large. The most frequent substances for EDM include cold and hot rolled steels, carbide, titanium, brass, copper or high-temperature alloys. Any material used in EDM must be conductive for the process to work.

Benefits of EDM Machining

EDM machining can be used to cut extremely hard conductive materials that can prove challenging with other machining methods. The finish is very smooth, with no burrs or rough patches so EDM is an excellent choice when finish or appearance matter in the final product. EDM can also reduce production time and unit cost by using stacked parts or multi-up fixtures that enable multiple parts to be processed simultaneously for increased throughput from a single machine. The precision inherent in the EDM process allows complex designs to be machined cost effectively, even if they have thin walls, sharp corners, rounded corners with a small radius, extremely tight tolerances, or complex geometry including narrow slots and multiple holes. Using EDM eliminates the need for special tooling and reduces scrap due to shearing or breakage during the machining process. Because EDM does not use force for cutting, it enables machining of extremely small or fragile items that would be difficult to manufacture using other methods. Once the EDM equipment has been set up, it can run for long periods with little or no operator oversight, allowing manufacturers to use skilled operators across multiple jobs or work orders at the same time.

About Micropulse West

Micropulse West is a leading EDM and CNC machining company that delivers the highest quality and most advanced EDM/CNC solutions and services. We are committed to assisting clients in the aerospace manufacturing field reach their efficiency goals while adhering to mandated regulations. We also extend our services to the automotive, retail, military, medical and electronic industries to help them gain a competitive edge over their competitors. Contact us today to discuss your manufacturing needs!