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How to create a silver sculptural trophy

Sterling silver Perpetual Trophy for Buick Open golf event

Malcolm DeMille Inc. based in Nipomo, California, combines a combination of professions: jeweler, sculptor, artisan. MDI produces sculptural trophies, money clips, custom jewelry and accessories, for over 25 years. You can find custom DeMille pieces in many different fields, ranging from sports like golf, tennis, and football to major corporations like John Deere, Wachovia, and Jaguar. From one to a hundred, all work is designed by Malcolm himself.

Tiger Woods with Buick Goddess Trophy
The proud winner of the Buick Open 2006 (July 31-Aug 6, Warwick Hills Golf & Country Club).

Marketing consultant Momentum Worldwide commissioned Malcolm DeMille to make a one of a kind sculptural trophy for the three Buick sponsored events of the PGA Tour (the organization of professional golfers). In the Summer of 2002 Malcolm DeMille created a high-end piece of art, extensively utilizing his DeskProto software. The resulting "Buick Goddess" trophy has been awarded to several champions, like Tiger Woods, Sergia Garcia, and John Daly.

Freeform wirecut screenshot
Freeform smooth tool screenshot
Two Freeform screens, showing the wirecut tool and the sculpt tool.

DeMille began this immense project starting with rough hand drawings. These original sketches were scanned and then brought into the Sensable Freeform modeling program. By following the 2D sketches with Freeform's wirecut tool a rough 3D shape was created.

The Freeform program is integrated with Sensable's Phantom haptic arm tool (also see the Freeform Fish project), which lets DeMille sculpt with the added sense of touch. Sensable's Freeform program allowed DeMille to easily modify and stylize the Goddess to his satisfaction.

Screenshot of Freeform rendering
DeskProto screenshot of part and toolpaths
Final rendering in Freeform, and some toolpaths in DeskProto.

Once the 3D CAD geometry had been completed it was split up into a number of separate parts, as the sculpture was too complex to machine in one piece. Also casting in one solid piece was not possible; a hollowed out area was needed to maintain a consistent thickness necessary for successful casting.
For each part the geometry was transferred to DeskProto using an STL file. For most parts the toolpaths were created using DeskProto's Two Sided milling option.

The milling machine in action
Wax model after finishing
Machining a wax model, and the partially assembled wax model after milling.

Each of these parts was machined in blue carving wax on a Minitech 3 axis CNC milling machine. After machining the final details were added by manually carving and shaping.

As more than one Trophy needed to be created, these wax models have been replicated by making molds (in the metal casting process the wax model is lost). This replication is done by injecting molten wax under pressure into a mold made of silicone rubber. To make things more confusing; this mold is created by casting too: the silicone rubber is cast around the original machined wax part. As DeMille explains on their website, the process is "Easy as 1, 2, 3....4, 5, 6, 7, 8, 9, 10, 11, 12".

Detailing the wax model by hand
Pouring red hot metal
Carving details in injected wax (test assembly), and pouring molten bronze.

After detailing each wax-part, gating and sprues are added to the piece for feeding metal and venting of air. Refractory plaster investment was poured over the wax, then sat for approximately 6 hours. Dewaxing was done next, by steaming the wax from the investment: leaving a void the shape of the Goddess. During the specific firing time, the investment was dried and heated to 1400 degrees, where all impurities were removed. The metal (Bronze) was then heated to approximately 2000 degrees and poured into the investment mold.

Once a part is cast the investment is broken away from the part, and the gating and sprews removed. Next the parts were sandblasted and welded together. The welds were ground down flush, sanded smooth and polished to give the Goddess its sleek look. Last, the Goddess was Rhodium plated (a Platinum group metal) to its final finish.

The resulting perpetual trophy
The resulting Perpetual Trophy

The very first "Buick Goddess" piece created was cast in sterling silver. It was about 16" in length, mounted to a black granite stone base with sterling silver accents. It has been received with great accolades (see the illustration above). Three of these pieces have been made; one for each of the Buick sponsored PGA Tour events to be used as their Perpetual Trophy (each winners name is engraved around the base).

After the Perpetual Trophies were completed, a smaller version was created to be used as the Winners Trophy for each annual tournaments. These trophies were cast in Bronze, ground and polished and then Rhodium-plated, as described above.