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Sinker 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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How Sinker EDM Works

01 Setting Up the Machine

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

The sinker EDM electrode tends to create a textured surface on the walls of the cavity. This may be minimized by “orbiting” the electrode at a lower power level – the equivalent of doing trim passes with wire EDM. Post-processing, such as polishing, is often used to quickly improve the surface quality of the cavity.

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What Are the Pros & Cons of Sinker EDM?

Advantages

  • High Precision & Accuracy

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

  • Material Versatility

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

  • Complex Geometries

    Sinker EDM can produce cavities in curved or angled surfaces and can burn deep holes with high aspect ratios that are challenging for traditional machining methods.

  • Non-Contact Process

    The sinker EDM process creates burr-free holes and leaves no physical stress on the workpiece. Snker 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 sinker EDM process can only machine electrically conductive materials like metals and certain alloys, not plastics or composites.

  • Slow Process

    Sinker EDM burning 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 machining due to specialized equipment, energy consumption and labor time.

Applications of Sinker EDM

Sinker 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
  • Small medical components
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What Materials Can Be Processed Using Sinker EDM?

Like wire EDM, sinker EDM 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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