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This Unique Settings ring is an excellent design for
palladium with heavy, low-profile prongs for the 1.50 carat center
diamond, ample wall thickness for setting the baguettes and supporting
the overall structure and sufficient room for bead setting the small
round diamonds and bright cutting along the sides. This ring mounting
is an ideal example for an overview of step-by-step palladium manufacturing
techniques. |
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The original model is made with some shrinkage taken
into consideration. Only after a model is perfected and tested, is
it introduced into the Unique Settings line. For this piece, technicians
at Unique Settings calculated about 1% or less shrinkage from the
original model to the finished replica cast in palladium. They attribute
this to the use of silicone for their molding procedures. This is
especially important for setting tolerances (depth, width and size
of bearing walls) for the channel set baguettes and bead set rounds
with bright cuts. This wax was injected into a silicone mold. After
it solidifies, cools and removed from the mold a wax model specialist
examines it, removes the parting lines and other surface inconsistencies
and then prepares it for casting. |
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The main gate or sprue is about 4.5 millimeters in
diameter and attached at the heavy shank on the bottom portion of
the ring. For this model, 2 additional 1.8 millimeter feeder sprues
are attached within the finger hole below the top. These additional
sprues assist in quickly feeding the palladium to the heavier upper
portion of the ring since the metal is quick to solidify. Research
in palladium casting has shown that strategically placed multiple
sprues are a key factor in successful progressive solidification
(the metal cooling and solidification) and reduces or eliminates
porosity and cracking. |
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Unique Settings uses a large button tree structure
for casting multiple pieces. This image shows how the main and runner
sprues are attached to the casting base. More pieces will be attached
to the button to complete the 'tree'. |
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The palladium is melted by induction and is protected
by argon to reduce its exposure to the atmosphere. When molten, palladium
absorbs considerable amounts of oxygen and hydrogen. The argon works
as a cover gas because it is heavier than air and shields the molten
metal from the atmosphere. The Unique Settings casting expert opens
the chamber and carefully stirs the molten metal with a quartz rod
to insure distribution of the elements. After, the chamber is secured
and the pieces are cast. |
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The arrow indicates the project example on the casting
button structure. Progressive solidification is a general description
for the metal cooling and solidification cycle within a cast mold.
Essentially, the metal should cool and solidify from the top of the
tree (where there is a lesser quantity of molten metal) toward the
button. The modified tree structure, feeder sprues and proportionately
large button size help to insure success in this critical process.
1.
Palladium, like other metals shrinks after solidification. Because
all models are connected directly to the largest mass of molten
metal, there is an assurance that all models will have cast completely
and begun the solidification process well before the button solidifies.
2.
Palladium characteristically releases considerable gasses (which
it absorbed in molten state) during solidification. The feeder
sprues in this structure not only allow for efficient flow of molten
metal into the model, but also provide additional venting for the
release of gas.
A thinner button would have solidified first causing
the shrinkage and gasses to be trapped within the jewelry models
causing pitting, porosity or incomplete or misshapen castings.
Eliminating the feeder sprues would also jeopardize the success of
the models with through-and-through porosity from trapped gasses. |
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After casting, the Unique pre-finishing department removes the
sprues and gates by sawing. |
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The remainder of the sprues is removed by filing and sanding.
The ring is then rounded and overall pre-finishing begins. |
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For pre-finishing, the Unique technician uses rubberized abrasives
to smooth the inside of the ring. Sanding sticks, files and other
abrasives are used on the outer surfaces. Because the cast models
are free of pitting, there are no problems in the pre-finishing process.
The ring is then sent to the polishing department for pre-polishing
prior to setting. |
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With the pre-polishing completed, the ring goes to the in-house
stone setting department where the diamond baguettes are channel
set. Opposing bearings are cut in the palladium side walls with a
bearing bur. The baguettes are then "slid" into place from
the top portion of the ring. There was no porosity in the model to
interfere with the setting process. This image shows the baguette
setter burnishing the sidewalls with a fine pointed burnisher. |
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For the final tightening, the setter uses a reciprocating hammer.
The hammer is set to the lowest setting and provides sufficient impact
for final tightening. |
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With the baguettes secured, the next step is the bead-and-bright-cut
setting of the round side diamonds. The small round holes are made
larger with a round ball bur that is about the same diameter of the
diamonds being set. The diamonds are seated with a 0.10 millimeter
spacing between them. The stone setter completes the setting of the
small rounds. Again, because this model is porosity-free, the setter
was able to raise substantial, consistent beads to secure the diamonds
with no problems. |
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Next the large round center diamond is set. The first step in
this process is to reduce the dimension of the upper gallery wire
with a large round ball burr. |
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Next, a 90 degree bearing burr is used to create the bearings
in each of the 4 heavy prongs individually. The metal flashing created
by burring is removed and the diamond is set using pliers and then
secured by hammering for final tightening. With palladium's desirable
malleability, the prong bending and forming was trouble-free. |
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After setting the ring is sent to the polishing department for
final finishing and polishing.
This mounting is ideal for palladium
due to the following desirable features:
- The center
diamond is set at a moderate height and in heavy prongs which
will remain secure through normal wear.
- The four center diamond
prongs are supported by a sufficient upper gallery wire.
- The wall thickness of the channel walls was ample enough
so that after the bearings were cut for the baguette stones
the thickness that remained was substantial for setting and
support of the ring structure.
- The setting area for the small
round diamonds allowed for enough metal to grave significantly-sized
beads that will secure the stones during normal wear and
to apply an attractive bright cut to reflect their brilliance.
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