Plunge EDM: a definitive guide

Plunge EDM: a definitive guide

Electrical discharge machining (EDM) is a specific type of precision machining that’s used to create parts from a variety of metals. It’s referred to by many different names, but the two most common are:

  • Conventional EDM
  • Sinker EDM

The technology creates the required shape by plunging or sinking an electrode into the metal to create a very precise cavity – hence how it gets its name – plunger sinker.

What is Plunge EDM used for?

The process is used to form parts for a wide variety of applications. It’s a highly intricate technology, meaning it’s suitable in many situations. Some typical uses include:

  • Fine surface finishes to 10 micro inches
  • Sharp corners
  • Blind keyways
  • Thin walls and cross-sections
  • Blind cavities

It can be utilised with many types of conductive materials. This includes steel, copper, brass, aluminium and titanium, as well as other exotic metals that present problems in more conventional machining.

The process takes advantage of all moveable axis, meaning it can create very complex, 3D shapes, as well as simple geometries.

How does Plunge EDM work?

The process creates machine parts by discharging electrical energy from an electrode into the metal. Both components are submerged in dielectric fluids to do so, and the current is applied automatically by a pre-programmed controller. The sparks jump from the electrode to the material, causing the metal to heat and melt into the precise required shape – a process known as ‘spark erosion’.

The electrode is commonly made from tungsten, copper or graphite and is formed as a mirror-image of the part to be produced (the same as with other EDM production technologies).

Comparing Plunge EDM to other technology

Plunge EDM is often used as an alternative or in conjunction with wire EDM, with both using spark erosion to form the desired shape. The difference lies in how they do this and can be defined as follows:

  • Plunge EDM sinks the shape into the material
  • Wire EDM uses wire to burn the geometry into the material

One huge advantage of Plunge EDM machining is its high level of precision. As opposed to wire EDM that’s designed around production speed and low maintenance, Plunge EDM brings unprecedented levels of reliability and accuracy. While both are highly advanced methods of precision machining, Plunge EDM has evolved to produce the scrupulously exact copies necessary for parts with little-to-no tolerance. In addition, wire EDM can only create 2D parts, whereas Plunge EDM has 3D capability.

As such, the process is often used for machining highly technical parts, including those used in satellites and spacecraft.

The one disadvantage to the technology is the time it takes to fabricate the electrodes. These also wear with use, meaning longer-term production runs may require additional ones.

EDM Plunge is one but one type of advanced precision machining on offer from WA-based company, SixDe. Our end-to-end solutions model allows us to determine, design and produce the appropriate method of machine production that’s bespoke for our customers’ needs.

From precision machining to CNC, wire EDM to EDM Plunge/Sinker and more, we offer the advanced, home-grown service that Australian companies can rely on. Get in contact for more information.