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Bonding... how do they do that?


#1

A number of wedding band manufacturers make mixed metal wedding
bands. When working on those bands it’s clear that no solder was used
to join the different metals. The seams are perfect, with no pits or
gaps and they don’t separate when heated or bent.

How do larger jewelry manufacturers do that? Is there any way to do
it yourself in a small shop? I imagined it’s some sort of fusing
process but it seem as though there is little distortion of the
components during fusion. Even in a kiln I wouldn’t think it would
be that clean. Does anyone know how it’s being done?

Below is a little blurb from a Novell ad. This happens to be a gold
& silver band but they do this with white gold & yellow gold, gold &
platinum…etc…

Novell’s new In Union wedding bands are made by pairing 14KT Gold and
Argentium Silver with a very unique bonding technology. A
light-weight gold band is designed, finished, and carefully fused to
a strong Argentium Silver liner. This results in a wonderfully
resilient product with great potential for color, design, and
flexibility.

Mark


#2
A number of wedding band manufacturers make mixed metal wedding
bands. When working on those bands it's clear that no solder was
used to join the different metals. The seams are perfect, with no
pits or gaps and they don't separate when heated or bent. 

How do larger jewelry manufacturers do that?

I read Mark’s post last Sunday, when I’m not inclined to linger over
the computer, and it awakened a foggy, 20 year old memory of
something I read in JCK. And I thought, “Somebody like JB will
probably reply anyway…”

The majors use all sorts of techniques like diffusion bonding, which
is how= mokume is done, to do various trick things. How those bi-and
tri-color bands are (or can be) made is even more trick, which is
what the article wa= s about, long ago. BTW, I looked at Gold
International Machinery this morning, but they don’t have anything
related to this question at the moment.

You get yourself what amounts to a lathe bed with ground ways and
all. Then you get two indentical electric motors mounted on those
ways, facing each other (this is the concept, not a how to) on
precisely the same center. And they have chucks to hold your work.
The motors both spin the same, either CW or CCW, but since one is
right-handed and one is left-handed, they are spinning opposite each
other. You mount your work in both chucks and bring it up to speed,
which I don’t know the RPM but it’s high. When they are up to speed,
you use a lever (hydraulics, I’d think) to bring the two parts
together with great force The friction of all that bonds the two
parts together almost instantly…

That was the article, but I’ll point out some obvious, “Don’t try
this at home” things. One is that there must be a clutch or the
whole thing will just explode when the parts seize. The other is
that an inert gas atmosphere would be recommended if not essential.
Finally, I imagine it took a lot of failures before the right speeds
and forces were figured out.

Much of the rest of that sort of work is done by simple pressing - a
white gold band with a groove down the center is made size 6, and a
yellow gold band that fits the groove is made size 6 1/4. They’re
assembled and stretched to size 7, which locks the whole thing
together like magic. Easy but they’re using machinery, not a bench
ring stretcher. You can do a lot with one of those, too, though.


#3

It is diffusion bonding, there are several ways to do it but in
essence the metals are put in intimate contact within a graphite die
and using some form of press (air or hydraulic) The die is heated
(normally by induction) and the atmosphere is carefully controlled
around the ring. The heat and pressure cause the metals to fuse.
There are several machines made in Germany that can do this but they
are all quite expensive ($70,000.00) It is an industrial processes,
you have to make a lot of work to pay for such a machine.

James Binnion
James Binnion Metal Arts