Carbon Graphite EDM

Carbon graphite EDM materials are made entirely of carbon. They combine the strength, hardness and wear resistance of carbon with the corrosion resistance and self-lubricating properties of graphite. Carbon graphite properties have excellent corrosion resistance and are capable of operating at temperatures exceeding 315 °C for extended periods of time, depending on the specific grade.

Carbon Graphite EDM Advantages

This unique material has numerous carbon graphite machining benefits that make it the most widely used for EDM applications. Some of main benefits of utilizing carbon graphite properties for EDM machining, include:

  • Has a low coefficient of thermal expansion (3 times lower than copper) which guarantees stability of electrode geometry during electro discharge machining.
  • Available in large blocks.
  • Does not melt, but goes directly from the solid state to the gaseous at 3,400°C,

which reduces wear.

  • Density is 5 times lower than that of copper, which results in lighter electrodes.
  • Easy to machine.
  • Very resistant to thermal shock.
  • Provides a higher metal removal rate than copper with less wear.
  • Possesses the unique characteristic that the wear ratio tends to decrease as the peak current increases.

Carbon Graphite Properties

There are several physical carbon graphite properties that separate carbon graphite EDM from other types of materials, these include the following:

  • Density – The wear rate of carbon graphite EDM decreases and the surface finish improves as the graphite density increases.
  • Grain Size – By using very fine grain graphites, the overall wear decreases and the surface finish improves. However, prices increase, and removal of material is lessened through this process.
  • Electrical Resistively - The lower the electrical resistivity, the higher the thermal conductivity. Therefore, the graphite can dissipate the energy accumulated during each discharge. Thus, the wear rate decreases with electrical resistivity.
  • Flexural Strength - The higher the flexural strength, the easier the fine detailed machining and the lower the wear.
  • Hardness - The higher the graphite hardness, the more difficult it is to machine the electrode.
  • Settings - Graphite used in negative polarity gives a faster machining speed than positive polarity with a wear rate of about 20% regardless of the intensity level. 

Carbon Graphite EDM Classifications

Carbon graphite properties are classified by their particle size. Particle size is used because most of the other properties and characteristics of carbon graphite EDM are directly or indirectly related to particle size and orientation. Carbon graphite machining EDMs fall into the following five particle size classifications:

  • Angstrofine (less than 1 micron)
  • Ultrafine (1-5 microns)
  • Superfine (6-10 microns)
  • Fine (11-20 microns)
  • Medium (21-100 microns)

It is important to remember that not all manufacturers make carbon graphites that fall into all the above classifications. Premium carbon graphite properties, those with a particle size of 5 microns or less, are difficult to manufacture.

Angstrofine Carbon Graphite Properties

Angstrofine carbon graphite machining EDM material provides an isotropic uniform structure that provides very high strength. It is often used for fine detailed engraving jobs, extremely delicate and fragile electrodes or jobs requiring the best possible surface finish. The advantages associated with angstrofine carbon graphite EDM, include:

  • Excellent MRR
  • Low electrode wear
  • Unexcelled flexural strength
  • Superior for wirecutting
  • Good machinability

Ultrafine Carbon Graphite Properties

Ultrafine carbon graphite provides an isotropic nature combined with a high strength uniform structure. Applications include: minimum-taper cavities, detailed engraving jobs, molds and dies and jobs requiring superior surface finishes. The advantages associated with ultrafine carbon graphite EDM, include:

  • Excellent MRR
  • Superior wear resistance
  • Outstanding flexural strength
  • Consistent quality
  • Readily available
  • Very good machinability
  • Available in large sizes

Superfine Carbon Graphite Properties

This medium strength isotropic carbon graphite machining EDM material is used for forging dies that require larger electrode sizes. It can also be used for jobs that require a good surface finish and diecast dies. The advantages associated with superfine carbon graphite EDM, include:

  • Available in larger sizes
  • Good machinability
  • Can be wirecut
  • Economically priced

Fine Carbon Graphite Properties

Fine carbon graphite machining EDM materials provide lower strength and less of a uniform structure and are used for jobs that require thin sections or strengths. They are also used for larger electrodes, for forging dies or roughing electrodes. The advantages associated with fine carbon graphite machining EDM materials, include:

  • Available in large sizes
  • Low material cost

Medium Carbon Graphite Properties

Medium carbon graphite machining EDM materials contain a non-uniform structure and are used for jobs that require very little detail or for high-amp metal removal electrodes. The advantages associated with medium sized EDM materials with carbon graphic properties, include:

  • Available in large sizes
  • Low material cost

Contact American Wire EDM for Advanced Carbon Graphite EDM Machining Today

Contact us for more information regarding carbon graphite properties and advanced carbon graphite EDM processes, or request a quote today.