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Plunge EDM

  • Make Complex & Irregular Cavities in Metal

  • Cut Shapes That Are Impossible to Machine

  • Ideal For Short Run/High-Mix Projects

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Harley Davidson
3M
Sanmina
Smith & Nephew
Medtronic
“We were really struggling to find anyone who could cut a certain type of heavy-duty glass. Everyone told us it couldn’t be done, so when we reached out to Fathom, we expected to hear the same thing. Instead, a few days later, they called back with a plan. They had tracked down the people who actually developed that glass and worked directly with them to figure out a solution. That’s the type of approach we have come to know from our Fathom team.”
Lead Engineer
Defense Contractor
“Working with Fathom has given us a level of supply chain control we haven’t had with other partners. Instead of juggling multiple suppliers for machining, sheet metal, extrusions, and 3D-printed prototypes, we can run everything through one team and that’s been a huge advantage for our EV programs. Their engineers helped us tighten up a machined cooling-plate design, turn around sheet metal brackets in days, and rapidly iterate several 3D-printed enclosure concepts early in development. Having all of these capabilities under one roof has reduced delays, improved consistency across assemblies, and cut a significant amount of coordination time on our side.”
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Major EV OEM
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EV Systems Supplier
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Consumer Technology Company
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Crown
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3M
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Sanmina Corporation
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How Plunge EDM Cutting Works

01 Setting Up the Machine

Plunge EDM, also known as ram EDM, cavity EDM and sinker EDM, uses a specially-shaped electrode to carve complex cavities in conductive metals. It can also form deep ribs and sharp inside corners, ideal for building molds. The first step of this process is to design the electrode, which is formed in the negative of the shape of the hole you want to create. This method can be used to create complex and even irregular shapes

Plunge EDM_SettingUpMachine
02 Sinking the Die

The workpiece and the electrode are submerged in dielectric fluid. The electrode is slowly lowered (or sunk) toward the workpiece. As it gets close to the surface of the workpiece, a spark jumps the gap, eroding the workpiece. The electrode is slowly lowered until the desired cavity is created. The dielectric fluid helps to keep the workpiece cool and acts as an insulator. It also removes metal particles from the workspace.

Plunge EDM_Sinking the Die
03 Finishing Passes

When this process is completed, the part is removed from the dielectric fluid. It should be washed to remove any unwanted residues. The part can then be inspected to ensure that the cavity meets your requirements. Lastly, the part may need some post-processing before use. The EDM process may cause minor pitting on the surface of the part. It may require post-processing to achieve a smooth surface.

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What Are the Pros & Cons of Plunge EDM Cutting?

Advantages

  • High Precision & Accuracy

    Plunge EDM is capable of drilling very small and precise holes, often down to a few microns in diameter.

  • Material Versatility

    It efficiently drills through extremely hard materials like hardened steel, tungsten carbide and superalloys, which are difficult for conventional methods.

  • Complex Geometries

    Plunge EDM can produce holes on curved or angled surfaces and create deep holes with high aspect ratios that are challenging for traditional drills.

  • Non-Contact Process

    The plunge EDM process creates burr-free holes and leaves no physical stress on the workpiece. Plunge EDM is not limited by material hardness or brittleness. It’s ideal for high-mix, low-volume production projects. Electrodes are easy to manufacture, because they don’t need to be harder than the material they are going to cut.

Disadvantages

  • Limited to Conductive Materials

    The plunge EDM drilling process can only machine electrically conductive materials like metals and certain alloys, not plastics or composites.

  • Slow Process

    Plunge EDM drilling can take several minutes per hole, making it unsuitable for high-volume production

  • Electrode Wear

    The electrode wears down during the process, which can be significant and may require replacement or maintenance.

  • High Cost

    Both the initial setup and operating costs can be higher than conventional drilling due to specialized equipment, energy consumption and labor time.

Applications of Plunge EDM

Plunge EDM fills unique needs in many industries. Here are some examples of its versatility:

  • Tool and die making
  • Injection mold tool fabrication
  • Sharp inside corners
  • Deep and thin ribs
  • Blind keyways
  • Internal splines, squares or hexes
  • Machining threads into hardened parts
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What Materials Can Be Processed Using Plunge EDM?

Like wire EDM, plunge EDM cutting can only be used with electrically conductive metals, including these:

  • Copper
  • Carbide
  • Tungsten
  • Bronze
  • Carbon steel
  • Inconel
  • Stainless steel
  • Hastelloy
  • Kovar
  • Titanium
  • Carbon graphite
  • High alloy steel
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Explore Fathom’s Full Range of Manufacturing Equipment

Download our complete machine list for a detailed look at our capabilities across CNC machining, additive, molding, and fabrication.

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Why Our Customers Choose Fathom

  • Our expert engineers will help you optimize your part designs for production.
  • Our engineering and production teams bring decades of expertise and problem-solving to every project.
  • We offer manufacturing and full post-processing capabilities under one roof for one point of accountability
  • We’re your partner from design and prototyping to bridge and full production.
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