Marshall ;
Their are a couple type of spray metal units on the market. The one I am most
familiar with uses and electric arc produced between 2 electrodes. A feeding
mechanism similar to a MIG welder feeds the kirksite or copper wire into the
arc. Compressed air sprays then vaporized particles onto your workpiece. The
effect is similar to spray painting out of a spray can. You can actually
spray your hand if you like (notice I said your hand 'not mine'). You just
wouldn't want to stay too long in one spot. They usually start out with
several light coats over the SLA master so as not to overheat the part enough
to warp it. In later coats they usually turn up the power to build up faster.
It take a couple or 3 hours to get an 1/8 inch or so coating onto the part.
The whole thing is then backfilled with epoxy or low temp alloy filler from
behind. They usually lay copper water lines into the cavity then pour the
filler over them for mould cooling. The SLA master is normally distructively
removed from the mould after the backing is in place. This method is very
good for very large parts. To visualize a good candidate for this process
think about how you would spray paint the cavity (opposite of the part).
Chances are if you can't reach all the areas with a part with spray paint,
you wouldnt be able to do a spray metal mould either. Thin details like ribs
are a problem also since you wouldn't be able to pick the SLA pieces out of
the finished mould. It is best to have some who does this for a living look
at your parts( we only do 3D Keltool and CNC cut Alum.). Spray metal is used
mostly today on automotive prototypes for valve covers, timing belt covers,
housings, etc. The mould life is about 1/4 of what a T6 aluminum mould would
be. Usually under 100 good parts before it deteorates quickly. The molds are
usually unrepairable.
Good Luck
Bob Morton
Fusion Engineering
In a message dated 11/22/99 2:16:16 PM Central Standard Time,
Marshall@Ennex.com writes:
<< Good morning,
Does anyone here know the physics or the metallurgical theory behind
spray metal tooling? I'm interested in )understanding how a powder metal
spray can be applied to a plastic surface and form a dense solid without
melting or burning the plastic. Your insights will be appreciated.
Thank you.
Best regards,
Marshall Burns
President, Ennex Corporation >>
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