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Seamless platinum bands


#1

Hi Guys,

I was talking to a friend the other day and he mentioned that he was
making a number of seamless platinum wedding bands.

The starting point was to make a perfect band out of sterling,
polish it up to a high polish, then make a rubber mould, then cast in
platinum.

How common is this practice?

Just curious.
Regards Charles A.


#2

I was talking to a friend the other day and he mentioned that he was
making a number of seamless platinum wedding bands. The starting
point was to make a perfect band out of sterling, polish it up to a
high polish, then make a rubber mould, then cast in platinum.

Why Bother, just bend up and fuse, No seam

The GOF
www.sabushkadesign.com


#3
How common is this practice? 

That, or some variation, is how most commercially made cast jewelry
is made. If the original model is carved in wax (increasingly common
these days, by use of CAD CAM mills or RP machines, you still then
end up with a cast metal piece, which often is done in silver, but
which may also be brass, nickel silver (uncommon for cast models,
more common for fabricated ones) or even pewter (again, more common
for fabricated models). That’s then finished to desired degree, and
molded.

For high volume manufacturers, there’s a whole other step. The
original model is made or cast from a wax, and molded. Then a series
of castings made from that first mold are sized to the range of sizes
the ring will be sold in (sizes of these are adjusted for various
shrinkage factors…), and these second generation castings are
themselves molded, sometimes many times, to produce the final
production molds. This way, the original single model ends up as the
model for a whole range of finger sizes, and depending on production
needs, each size may be represented by many copies of that mold from
the second generation models.

Many, if not most, jewelers and smaller scale manufactures do it
with just the single mold from the first model, sizing the resulting
wax models as needed.

of course, then there’s the other way, which is simply to initially
make the desired ring in the desired final metal, in this case,
platinum. With platinum, since seams in a shank or plain band can be
truly welded, instead of just soldered, it’s quite possible and
straight forward to produce a plain wedding band that does not have a
seam, since after welding, perhaps a bit of forging, and
re-annealing, the metal can be quite uniform in structure with no
discontinuity where it was welded… The main advantages of doing it
in silver, and molding and then casting the piece is that there may
be less waste produced (though a plain wedding ring need not produce
a lot of waste to fabricate), and then you have the mold in case you
ever need to make another. The fabricated ring, however, will often
be better metal, since forged and rolled and worked metal, especially
platinum, benefits greatly from this working, giving you a denser and
less porous (two ways to say the same thing) metal, with finer more
uniform structure. It may, as a result, be a ring with a much
greater durability and expected life span than the cast equivalent.

Peter


#4

Just as easy to make the band in platinum which saves you from
dealing with the inherent porosity issues of the casting. May be
more important it the metal savings. You are either tying up 20+ dwts
for the button or paying 30% over market to the caster. Add in the
casting time (if doing yourself) and mold time and it doesn’t make
sense. If you are making 100, possibly, but if you are dealing in
those quantities just order them from Nordt. One or two, no way. Tim


#5

Charles, I think that typically, seamless bands that are mass
produced are turned on lathes from tubes, not cast. But the practice
of making your master model out of silver, molding it and then
casting subsequent pieces from injection waxes from that mold, in
whatever metal you choose, is a very old practice. It’s one I’ve
been thinking about lately because so many manufacturers and small
shops are turning to CAD software that it seems the skill of the
master model maker is one that is fading fast. It used to be that
most pieces of manufactured “fine jewelry” were originally made by a
master model maker who would make that original model in silver,
then mold it. Now it’s almost all CAD. In my mind, the skills of
those masters far exceeds the skills of the current crop of CAD
operators (I say that eventhough these days I am sometimes a user of
the CAD software option). So many will look at a complex piece and
say that you couldn’t make it by hand, not by carving and casting or
fabricating. That the only way to make it is to use CAD/CAM.
Personally, I think that is rarely the only way to do it. There is
no doubt that CAD will work, but I do question that it is always more
cost effective, quicker and gives a better final product. That all
depends on the skill level of the yahoo’s doing the work.

Mark


#6
That, or some variation, is how most commercially made cast
jewelry is made. If the original model is carved in wax
(increasingly common these days, by use of CAD CAM mills or RP
machines, you still then end up with a cast metal piece. 

I suppose, but what these guys were doing was making the band to fit
the customer in metal first, making that perfect, making a mould,
getting a wax then getting that cast.

That’s what I meant.

Regards Charles A.


#7

surely its simpler just to fuse the rings… -bend the metal up,
roll down a piece of the same metal to as thin as possible and stick
between the joint and then melt together with a really hot torch!
(The thin sheets works almost like a solder) that’s how I make
seemless platinum bands without the need for casting etc

cheers
Annika


#8
I suppose, but what these guys were doing was making the band to
fit the customer in metal first, making that perfect, making a
mould, getting a wax then getting that cast. That's what I meant. 

Probably that just means they don’t have much experience in working
with platinum, so were avoiding possible errors of ignorance, which
can be costly when you mess up a bunch of platinum.

I do wonder why they bothered making the thing in silver first. Much
easier to just carve a wax, especially considering that platinum
castings don’t generally come out quite as smooth and pristine as
castings in gold and silver do, so they always need some significant
finishing work anyway, meaning a perfect polish on the model doesn’t
make much difference.

Making the model in silver does let the customer see a model that
looks more like the final ring does, and it’s a bit easier to see if
the size if going to be right. But then, with a rubber mold, and
injecting a wax, and then casting, you’ve then got multiple stages of
shrinkage to think about between silver model and final platinum
ring, so again, seems like wasted effort for this type of ring. As I
said, for more complex rings where a precise fabricated model can be
a much better model than a carved wax (think classical wire and
sheet constructions of basket heads, ballerina type rings, wire
clusters, and many more), THEN the initial model is better in metal
than in wax. But again, this is more for production work than a
single one time piece…

Peter


#9

Hi Peter,

I couldn’t understand it myself either, I too thought it would be
easier to carve a wax (or get one grown), however they’re very
experienced at using platinum, and they do forged bands as well as
cast bands.

There is a casting house I’m visiting tomorrow, to pick up a job (got
some precision gears grown in wax then cast in sterling), and these
guys have a very nice trade secret about casting platinum, and can do
a pretty nice job. I’ve got yo remember to pick up some wax samples
so I can send some to some people on the list.

I was just trying to figure out why they would make rings this way?

Regards Charles A.


#10
I was just trying to figure out why they would make rings this
way? 

Old habits die hard, perhaps…

Peter