Your question seems to be more related to doing production ring
castings in assorted sizes and not 1 offs or an occasional size
needed as might be neccessary for a store or an individual making a
special piece. Of course, one can always size each wax if the ring
was designed to be easily sized in wax. The problem is that many
have been designed for asthetics and not for the ease of sizing.
Some ring styles cannot be sized in wax at all due to the complexity
of shape that the top may have… in other words, when you adjust the
size, it changes the shape of the top of the ring in a manner that
makes the top of the ring not as nice as it used to be.
An example would be a thin flat topped signet ring size 6 with
engraving on the top. When you size that type of ring, you might be
able to get away with a maximum of 1 size up or down if you are
lucky. The top flat area will bend in or out depending on which way
you size it… then, when you attempt to flatten the top by
sanding/filing, you loose the thickness on top and you file away the
engraved detail. imagine what would happen if you tried to make the
size 6 into a size 10… you end up with a U shape instead of a flat
In a production factory such as ours, We have names for different
types of models used at different stages of production. When we make
a ring for a customer that we think will go into some form of
production, We always have to think that it may require sizes to make
it easier to sell to stores and individuals.
If you have CAD/ CAM or Rapid prototyping Capabilities, then you
simply make a new model for each size as needed. Make one first, make
sure everything is as perfect as possible. figure your ring size
shrinkage for mold making, Test a few pieces… then make the other
If you don’t have CAD capabilities and you want to do it the way
factories have been doing it for years.
Start by making a Master Model.
A master model will never be used to produce a finished product. A
master model is about 15% thicker, bigger than anything you have done
before with lots of room to adapt. This percentage is calculated
shrinkage through the master model stage and production model stage
and final product stage.
The master model will be molded and then you can size the waxes
coming out of the master mold and cast them into… Production Models
that are adjusted for mold making… you make sure that all the
stonesettings in the production model are designed with just enough
shrinkage so that after molding and casting, the stones fit with no
modification to the settings. As your customer orders different
sizes, you inject a wax from the master mold, adjust the wax to the
size needed, cast it, perfect the sized production model, mold it…
and you won’t have to worry about that size ever again since you now
have a production model and a production mold for that particular
size. A Production model is sized 1/2 size larger than the finished
showcase size needed for most normal rubber molds. A chart of the
process looks like this.
- MASTER MODEL:
- master mold
- Production models, size 4.5 ,5.5 , 6.5, 7.5, 8.5, 9.5 etc.
- Production molds of each size
- finished products in size 4, 5, 6, 7, 8, 9 etc.
Why is all this important? Well, if you have all the models made for
all the sizes you need, you can make molds for each size as you need
them… Now, when large orders start to come in, sometimes it is
neccessary to have up to 10 rubber molds of each size to keep up with
production orders and delivery dates. This is specially true if you
are planning to deal with large companies such as QVC or television
networks… department stores, large retailers or, you have a bunch
of sales people marketing your products. The other advantage of doing
this is that each finished ring looks just like the next size… no
difference other than the ring size.
If your not positive that your going to do volume, it’s still a good
idea to make a master model and then produce a single production
model of the size you want… you can play with the production models
out of the master mold… you can make mistakes and go back, cast
another one and fix the problem !!!
If you don’t do it this way, and you have a size 6 ring and size the
ring to a size 8, mold it… then cast the size 8 ring, due to
molding, casting and finishing shrinkage, the size 8 ring will look
smaller than the size 6 ring you copied. Retailers don’t like that
Hope this helps.
Racecar Jewelry Co. Inc.
We do casting, finishing, model making and a multitude of
different processes for our customers.
See our Adds on Ganoksin site.