Conveyor saves NUMMI $1.5 million
This GM/Toyota auto plant needs to move work in process 800 yards from their assembly line to a new paint shop. The solution saves money and floor space.
By David Maloney -- Modern Materials Handling, 9/1/1999
Painting processes have changed a great deal since the paint shop at New United Motor Manufacturing Inc.'s Fremont, Calif. plant was built originally in 1962. Those were the days when more emphasis was put on body fins and mirrors for hanging fuzzy dice than on long-life paint jobs with multiple coats, anti-chipping layers, and clear coats.In short, the facility needed an upgraded paint area for the 200,000-plus Toyota Corolla and Chevrolet Prizm cars built there annually. NUMMI is a joint venture begun 15 years ago by General Motors and Toyota.
"We looked at many different options for upgrading the passenger car paint area," says Ken McNees, managing engineer for NUMMI's paint engineering department. "The facility was well past its expected useful life. Our options included upgrading the existing shop or moving the paint system to another area of the plant. We finally decided to build a new system in a remote area of the facility."
To gain maximum efficiencies, NUMMI needed an efficient material handling system to convey car bodies from the assembly line to the new paint shop and back again, a total distance of a half mile. NUMMI chose an inverted power-and-free conveyor (Conveyor Tech 913-321-1100).
The system in place today saved about $1.5-million in installation costs compared to other handling systems considered, requires a minimum of floor space for operation and to store its compact carriers, and fits into the existing building shell.
Taking it to the paint
Cars ready for delivery to the new paint shop are known as unibodies (everything except windows, interior furnishings, and tires). They come off one of the two assembly lines in the plant. The other line builds Toyota Tacoma trucks.
At that point, the initial paint processes, including the anti-chip layers, have already been applied in the refurbished old paint shop. As the unibodies exit an oven there, they move to a pair of lifters and slide tables for transfer to the inverted power-and-free carriers.
There are 180 carriers in the system. Each has a unique bar coded license plate that is scanned into a tracking system.
"We can find any car, any place, any time," says McNees. "Our tracking system was expanded as a part of the upgrade."
When the carrier and unibody are positioned over the inverted power-and-free, a hook on the front of the carrier drops down and catches onto the moving conveyor chain. The system then pulls the unibody a quarter mile to the new paint shop. Once there, the hook disengages from the chain, and the unibody is transferred to a paint dolly for its ride through the new paint processes.
Upon completion, the unibodies again transfer back to the inverted power-and-free to return to the old paint shop, where they are scheduled for final assembly.
"This is a unique system," explains project engineer Jim Ellis. "Some of the components were right off of the drawing board. There were a few wrinkles to work out, but it has been running very reliably for us."
Compact carrier design
A major advantage of the power-and-free system, says Ellis, is the compact carrier design that reduces overall transport weight. Each carrier is only about 4 ft long compared to some designs that were 20 ft in length.
As a result, the system features lower power chain pulls, allowing for smaller and more efficient drives and chains in the system. In addition, storage space for the carriers is considerably less than that needed for the larger carriers, saving NUMMI valuable floor space, says Ellis.
Aside from their reduced length, the empty carriers are also designed to store at an angle instead of head to toe. Seventy-five empty carriers can fit into only 105 ft of storage space.
"The compact design allowed us to fit the system into our existing building shell. We could not have done that with other systems," says Ellis.
System at a glance
New United Motor
Manufacturing, Inc.,
Fremont, Calif.
x 4.5 million sq ft of manufacturing space
x Manufactures Toyota Corolla and Tacoma, Chevrolet Prizm models
x Output of 360,000 units annually
x 2,000 ft power-and-free conveyor from assembly line to paint shop
x 180 car body carriers
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