The five steps in jewellery casting process are as follows:
1. Wax model
The
casting preparation begins with the wax model. Based on the 3-D
rendition of the design, a wax model or resin material model is carved
or printed to represent the pattern of a finished piece of jewellery.
The model is then connected to a wax stem by a sprue to form a tree-like
structure to allow gold to flow through the “tree” with minimum
turbulence or resistance.
2. Investment
The
tree with the wax stem and attached wax models is placed inside a metal
flask and filled with plaster slurry to create an “invested” mould. Once
filled with the slurry, any air bubbles and pockets are removed by
“debubblizing” the flask inside a bell jar with negative atmosphere.
Once the plaster or investment material sets, it hardens into the
jewellery mould.
3. Burnout
The
hardened invested mould or flask is placed in a specialized kiln to
melt away the wax model at temperatures around 1600° F for 12-16 hours. A
well-burned flask has no remaining residue of wax or resin, only a
hollow impression or cavity left by the tree in the final invested
mould.
4. Melting and Casting
The next step
is to pour the gold or molten metal into the hollow cavity of the
wax-free mould. Various techniques such as centrifugal casting,
vacuum-assisted casting, or pressure casting (explained below in detail)
are used to ensure the gold flows evenly into the mould. The gold melts
at temperatures from 1,617° F to 2,006° F, depending on the alloy used
for varying colour and hardness.
5. Divesting
Divesting
is the last step in the jewellery casting process. At this stage, the
mould is put into a bucket of cold water to destroy the investment form.
Any remaining plaster is chipped away, leaving behind a tree containing
models as branches. The models are then cut free from the sprue. The
gold pieces of jewellery are now the exact replica of the initial wax
pattern. While the spruces are recycled, the jewellery is cleaned, set,
buffed, and polished.
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Source:https://www.jewelerstoolsmall.com/article-116-Five-Step-for-Jewelery-Making-Casting-Process-.html