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Drawing/Forming Dies
Loss of the tool's lubrication barrier between the die and worked part causes problems similar to those experienced in die casting
operations. The metal from the worked part galls and adheres to the surface of the draw or forming tool. The carbon steel electrons and worked part metal content have a natural affinity for each
other. This bond is usually inter-metallic in nature and can only be removed by re-polishing the tool. In doing so, part of the die steel is also removed in the process.
The micro topography compressive stress created during the MetaLL ifeÒ process is able to retain more lubricant than a polished or flat surface
and thus maintains
the needed barrier to prevent this covalent electron bonding from occurring between the
metals. The uniform micro-topography of the MetaLL ifeÒ also affords more surface area for the lube to adhere to than a flat one and creates greater heat dissipation at the die's surface without causing excessive lube build-up on the
tool. This increased heat dissipation allows the tool to run cooler thus extending the tool's life while increasing lube retention ability.
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The use of coatings in conjunction
with MetaLL ifeÒ
is also assisting in solving this problem, however, the substrate preparation is critical to preventing failure of the coating. Since most PVD (low temperature) coatings are very
thin and layed down in a crystal matrix fashion, they must have a good working base prior to
their application. It is critical, therefore, to properly prepare the
substrate by putting it in compression prior to application of the coating. MetaLL ifeÒ is the best
method for doing this.
Openings between
the crystal structure of the coating provide direct pathways to the
steel below.
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As die tensile
stresses build, these openings expand providing direct unprotected
pathways to the substrate material. If the substrate is not
protected, cracks develop causing the coating to also fail. |
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