What is EDM?
Electrical Discharge Machining (EDM) is a nonconventional metal removal machining method that employs the use of an electrode to machine the desired shape into a workpiece under carefully controlled conditions. EDM offers several advantages over conventional, “chip-making” machining methods including:
- The ability to machine extremely narrow notches.
- The ability to access hard-to-reach locations such as pipe/tube IDs without the need to section the workpiece.
- The ability to hold very close dimensional tolerances.
- The ability to machine harder materials and exotic alloys.
- The ability to machine irregular shapes not otherwise possible.
All conductive materials are able to be EDM’d. EDM notches can be machined on both the OD and ID of pipe and tube. Notches can be machined on IDs as small as 0.040”. Transverse (circumferential) notches are normally made with electrodes precisely ground to the respective radius of the workpiece. This ensures uniform notch depth along the notch length. Notches can also be made to match an irregular surface or have a thumbnail (semi-elliptical) profile.
Watch our demo video about the EDM notch creation process.
What are EDM Notches?
Electrical Discharge Machined (EDM) notches are produced by PH Tool using both Sinker and Wire EDM technology. Sinker EDM utilizes a carefully-made electrode to machine the desired notch. Wire EDM uses a traveling wire as the electrode. Think of the wire EDM like a sophisticated band saw, where the wire is the blade. The limitation with wire is the inability to machine captive notches – i.e. those that do not break out to the edge of a part. For captive notches, Sinker EDM is required. PH Tool has one of the largest concentrations of EDM machines in the country, with over 40 sinker machines and 6 modern, CNC-controlled wires. Many of our machines have undergone considerable modification and retrofitting in order to handle the unique needs of the NDT industry. These modifications include alterations to the power supply to allow cutting at extremely low aperages, thereby eliminating the recast layer normally associated with EDM technology. They are no longer general-purpose EDM’s, but rather highly-specialized, low-energy “Notch-makers.”
This means that we can handle a wide range of items, from tiny parts that fit in the palm of your hand to 10,000 pound components that would not fit within the envelope of a traditional EDM machine. We are not limited to what will fit in the work tanks. Tubular, bar, and rail standards can be as long as 40 feet.
What can be Notched?
Notches can be placed in any conductive material and can be shaped in a variety of ways. Hollow cylindrical items (tube and pipe) can be notched on the OD and ID, in axial, circumferential or off-angle orientations. Notches can be placed in welded components in the weld, toe, heat-affected zone, base metal, or even embedded in the weld. A wide range of items can be notched including, but not limited to: tube, pipe, bar, plate, wire, rod, engine components, structural aircraft parts, automotive parts, pistons, turbine blades, impellers, disks, hubs, springs and surgical implants.
What Widths are Possible?
EDM Notches used for Eddy Current, Liquid Penetrant and Magnetic Particle testing are typically very narrow, perhaps in the .004 - .005” wide range. Notches used in Ultrasonic Testing normally do not require notches this narrow. PH Tool has developed a proprietary method of machining Nano Notches as small as 0.0006” (15 microns) wide for applications requiring widths as narrow as possible. Refer to our page on Nano Notches for more details on this capability.
All of our EDM Notch Reference Standards are 100% inspected, traceable to the National Institute of Standards and Technology (NIST), and include a comprehensive certification report. At PH Tool, our dimensions are carefully obtained via replication and observation using video measurement systems, and contain reliable/repeatable dimensions which are NIST traceable.
More Info on EDM Notches:
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