If I carve a wide ring band in wax & want to make it in sizes 5-9;
I’ll carve the master in a size 9 & then make an RTV mold of it; size
the master wax down to a size 8 & make an RTV mold etc; I can’t size
this model all the way down to a 5 because it will distort. I usually
end up carving more than one master model to get the smaller range of
sizes but the two rings are never exactly the same. (Especially if I
carve a very intricate flower pattern) This drives me crazy!(Does
anyone have any suggestions / solutions?? Should I send the original
wax off to a CAD company to replicate the rings in different sizes?
Anything anyone could suggest would be greatly appreciated.
I would be happy to give you a quote on providing you with a set of
master waxes in various sizes. Usually I have a charge for the first
ring, then a much smaller price to duplicate the item in another size
or width (since the bulk of the programming has been done). If you
would like, I could take a look at what you are making, and see if I
can help. Intricate designs are a breeze with CAD-CAM! I’ve attatched
some pictures of work I have done in the past, they are small to make
downloading easier, but you can get the idea of the work!
The new one, design your ring in a 3d program and then cut a
selection of sizes. Or,if you want to hand carve it, do that, then 3d
scan it into a computer via a Roland MDX15 and a Fourth Axis rotary
attachment and then recut smaller or larger. Not easy to learn or
cheap to set up but you could get someone else to do it and you then
have a set of carving wax models to tidy up, and build in casting
shrinkages if necessary. This by the way is a great way to do
opposite handed designs for earrings or larger for brooches, really
accurate. Roland are discontinuing the MDX-15 at the end of the year
so they should be cheaper soon, and although they are not as accurate
as the more modern machines, the scanning function is a huge
timesaver.
The old way, works in two directions, I have not done this but I
have seen others get good results, and worked with the mould. If you
have an RTV mould and soak it in naptha it will swell, you can then
inject wax into it before it shrinks back to its original size. The
opposite of this is to mix naptha with the rubber before you pour it
around your ring, let it set up in an enclosed container and then
cut the wax out and let the naptha evaporate. It will then be
smaller, the only thing is you wont know quite how much and will have
to experiment with the mixture, ie percentages of naptha. I believe
it
is quite jelly like and has to be treated carefully. Also not good
for you to have the naptha evaporating off.
I knew a jeweller who would make small waxes and then expand them on
a smooth ring mandrel in a bowl of hot water before the injected
waxes had cooled too much. If this would work for your design you
could miss out every other size perhaps. Again I have not tried it,
sounds like it would take practice, but is very cheap to try!
It would probably be hard for even a well-equipped CAD company to
replicate your rings to your satisfaction. The 3d scanning process
has limitations in its ability to replicate tiny details accurately,
and it is difficult for the laser or touch-probe to get into all the
intricacies and undercuts you may have put into your carving. It’s
usually better to create the model directly in a CAD environment in
the first place. At that point, scale becomes irrelevant; you can
make it any size you want, and send it to a mill or 3d printer. It
will always be exactly the same model.
Another approach is to carve the flower pattern much bigger than the
final size. If this is a repeating pattern, you would just have to do
one module and scan that. The scanner will do a better job on a
larger pattern, and you can import the resulting scan into your CAD
program. Then it’s simple to scale it down, produce a left-facing
part from a right-facing one, and repeat it around your ring.