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CAD/CAM for a custom design gold ring

Wax model for gold ring with family crest (coat of arms)

Since over 30 years, Gary Swank Jewelers in Portland (USA) have been designing and creating unique pieces in gold and platinum for their customers. One of their specialities is custom designed rings incorporating family Coat of Arms. The example shown is for the Sawyer family, and features both their English Coat of Arms and the family name.

The original artwork
Wireframe in Rhino CAD
The original coat of arms image, and the ring design in Rhino.

The use of CAD\CAM technology offers great advantages for the design of such ring. Gary Swank used the Rhino CAD software. One of the features of this program is a function that creates a 3D 'heightfield' based 2D bitmap information: such heightfield was used to sculpt the crest. The ring's main body was created using Rhino's surface modelling tools.

To produce the 2D artwork, the client brought in their original Coat of Arms that was mounted in a wall case. Gary Swank took a picture of it to produce the 2D bitmap needed. This was actually done with several bitmaps, one for each part.

Rendering 1, in Rhino
Rendering 2, in Rhino
Rendering of the final design in Rhino.

The banner that has the name Sawyer was formed separate and did not incorporate heightfield surfaces. In the CAD model the banner simply floats above the ring, without a connection. This is automatically corrected during machining, as the cutter cannot create the empty space between banner and ring. See the picture of the result.
These renderings have proved to be very useful when presenting the design to the client: any changes that the client wants can still be incorporated without high extra cost.

Toolpaths in DeskProto
Toolpaths, detail
Rotation axis toolpaths in DeskProto.

Toolpaths then were calculated in DeskProto, for a very sharp conical cutter in order to also produce the most intricate small details. Also a very small distance between the toolpaths (stepover) for a high surface quality. The picture clearly shows DeskProto's use of rotary toolpaths: not just indexing (machining from several sides), but continuous rotation during machining.

Milling on the Align-Rite
Milling, detail
Machining the wax model.

Gary Swank uses a machine made by Align-Rite in Tucson (AZ).
Clearly visible are the 4th axis unit (rotary axis) and the very sharp conical cutter. Such cutter is of course very delicate, however as when machining wax the cutting forces are low this is not a problem. As a next step the wax model has been used to create the investment casting shell, a technology that already is used thousands of years.

The resulting ring
The resulting ring.

The final product has been cast in 14 karat yellow gold. Of course after casting manual cleanup was needed to remove the sprues used in casting. Finally the ring has been polished to achieve the high gloss result as shown above. The family Coat of Arms combines well with the ring shape, and the precision of both crest and banner would have been difficult to achieve without the use of CAD/CAM technology.

Swank ring No 90301
Swank Ring No 11115
Two more rings, created by Gary Swank using CAD/CAM technology.

Gary Swank also uses his Rhino / DeskProto / Align Rite system to produce other types of rings and jewelry. Gary Swank states as follows:
"While the quality and beauty of each piece of jewelry will always depend the skill of the jeweler, CAD helps us deliver precision at the foundation of the process. CAD accomplishes this precision by allowing us to view the design with stone "models" in place and produce a very precise "rendering". You can review the rendering and point out any areas you would like altered and we can fine-tune the design to your specifications. With CAD almost any design that can be imagined can be created: this brings the craft of producing custom designed jewelry to a new level."