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 Wednesday, June 23, 2010
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Carbide Machining Without the Worry of Binder Depletion

EDM is a popular means of machining tungsten carbide materials, because the hardness of the material is not a concern for the EDM process.  Both Wire and Sinker EDMs can used to machine fine details and near mirror finishes in tungsten carbide materials.  The major drawback to the use of WEDM to machine tungsten carbide has always been the electrolytic action between the carbide material and the dielectric (de-ionized) water used in WEDM machines.  This electrolytic action can actually break down the binder in the carbide, usually cobalt, and produce what looks like rust on the surface of the material.  Under magnification, this break down is apparent as voids in the surface of the material (see photo 1a & 1b).  These voids weaken the structure of the material, and will result in shortened tool life, especially for impact tooling such as punches, and dies used in stamping, forging, or cold heading. 

WEDM using oil as the dielectric has been a slow process, historically, and there have been few of these kinds of machines produced.  Makino now offers a machine designed to operate with oil dielectric, and to cut carbide and PCD materials with extreme accuracy and surface finishes.  The UPV3 and UPV5 WEDM machines are the next evolution of the award winning U-Series WEDMs from Makino.  Although designed for machining carbides and PCD materials, the UPV machines also perform well in tool steels.  Leaving only sporadic measurable recast, and no measurable HAZ, these machines can achieve measurable surface finish results of 0.08ymRz or better! (see photo 2).  For more information about these ultra-precise, oil dielectric WEDMs, watch the new Makino webinar on "Faster Cutting of Carbide and Hardened Materials."


Photo 1a – Carbide machined in oil; no cobalt depletion.



Photo 1b – Carbide machined in de-ionized water shows signs of cobalt depletion.



Photo 2 – Reflections of parts in surface of carbide block taken directly from UPV.


Cycle Time Reduction | High Speed Burning | Surface Finish
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