Finding acceptable production methods for large, one-of-a-kind metal parts can pose problems in terms of turnaround time, quality and economy. But there are contract manufacturers out there who find one-, two- or four-of-a-kind work challenging and an important aspect of their business.
Acme Metal Spinning, a well-known 100 year old metal spinning company, recently fabricated a large, primary outer ring structure for a unique, one-of-a-kind theater lobby decorative lighting chandelier.
Now hanging in the recently opened Pacific Theater of San Diego, California, the elegant light fixture is an interesting example of creative design and modern manufacturing processes. Housing 16 F50BX lamps and 8 two-lamp electronic dimming ballasts, the 6 foot diameter pendant is an energy efficient design, producing sufficient lumens to light the lobby area with a soft, pleasant glow. It is suspended 108 inches from the theater ceiling by 4 large brass chains. Its graceful contours, subdued colors and soft lighting blend beautifully into the coved ceiling design.
The light pendant was manufactured by Advent Lighting Corporation of Greenville, Wisconsin, manufacturer of specification grade architectural lighting. The theater pendant project began with KMA Architects and Engineers of San Diego, who originated the concept. Advent Lighting was then called in to produce the actual pendant assembly.
Because of the chandelier's size, the outer trim pan ring was necessary to provide the support structure for holding eight acrylic panels in place which formed the light fixture's globe. The ring, along with an aluminum T-bar, provided the base structure which gave the fixture the needed strength and rigidity for holding the l8 lamps and wiring assembly.
Since the chandelier was a one-of-a-kind undertaking, methods to produce the large outer component were limited. Extrusion processes couldn't handle the large width to length size material requirements. The seamless, smooth contours would be difficult to create using hand fabricating techniques. And because only one finished part was needed, stamping processes requiring expensive permanent tooling were ruled out, further limiting the manufacturing options. Advent Lighting decided to call in Acme Metal Spinning of Minneapolis, Minnesota to see if they could produce the needed outer ring.
"Metal spinning was the most practical method to use," reported Bruce Johnson, president of Acme Metal Spinning. "It's fast, provides a very attractive finished appearance and can be produced as a single part without the need for expensive, permanent tooling."
To fabricate the part, Acme began with two 130 inch square sheets of 0.190" thick aluminum. Cut to form a semi-circle, the two parts were welded together at the ends to form a donut-shaped flat piece of aluminum. Weld beads were ground smooth. Then Acme designed and produced a laminated wood tooling pattern. This is a standard process used in the metal spinning industry to produce tooling. What made this particular part and the tooling for it unique was its large size. Acme designed the tooling on its CAD system. The laminate wood structure was constructed and assembled with everyday woodworking tools and then machined to size on a 120" diameter lathe. Two workers were required to move and position the tooling fixture using forklift and overhead crane.
Once complete, the tooling was mounted in a Lieco 120 inch capacity spinning machine, one of the largest machines of this type in the United States. This process required just under 6 hours while the actual spinning process took only about an hour for the one part. The spinning operation combined rotation and force. Roller-like tools are pressed against the whirling blank as it turns on the lathe, flowing and forming the material around the wooden tooling pattern which was cut in the shape of the finished part. The finished part had a smooth, consistent finish, including the near invisible welds and required no additional finishing operations by Acme.
Following shipment to Advent Lighting, the part was sprayed with a bronze paint, assembled and made ready for hanging in the Pacific Theater. According to Acme, this was the largest light fixture component it has ever produced.
Exquisite lobby design esthetics in public buildings using metal spinnings isn't limited to lighting fixtures. The use of metal spinning for architectural adornment - functional and decorative - reach as far as the designers imagination. Case in point, large domes produced by Acme which were trimmed into halves to form the top end caps for two elevators in a Mid Eastern country hotel lobby.
The domes were produced from 3/16" thick, type 304 stainless steel blanks measuring almost 8 feet in diameter. As with the aluminum chandelier base, tooling was designed on Acme's CAD system. The wooden tooling was machined on a 120 inch diameter lathe.
Acme's spinning lathe for this job was customized to enhance the part size and overall finish quality. Acme used an annealing process during production to help relieve material stress and work hardening. Once shaped, the 72" dia. x 36" deep domes were polished to a number 4 finish, reflecting light with an unusual brilliance, adding a celestial look and feel.
Besides architectural and light fixture components, Acme produces air-moving, food processing, agricultural parts and cryogenic tanks. Its specialties are hemispherical and large diameter spinnings.