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AUTO MANUFACTURER IMPROVES CYCLE TIME FOR JIT COMPONENTS
New
United Motor Manufacturing is a joint venture between Toyota and
General Motors. The plant assembles Corolla automobiles and Tacoma
trucks. Recently targeted for an upgrade was a conveyor system that
services the output end of a stamping press line at the plant.
In this operation, employees transfer stamped body components such as
door panels from a stamping press to specially designed steel racks.
Once a rack is full, it is moved to a holding position. A lift truck
operator will then pick up the rack and carry it to the body assembly
line in another area of the NUMMI plant.
Because the assembly operations at NUMMI are based on the JIT
concept, the smooth, uninterrupted flow of stamped parts from the
stamping plant to assembly is critically important.  Conveyor system
reliability and uptime were therefore non-negotiable demands, regardless
of the design finally adopted.
The Stamping Plant's new system uses two parallel lines of two-strand drag-chain conveyor to carry empty racks to the loader platform
area. As empty racks reach the end of the infeed conveyors, a
right-angle powered-roller transfer moves them onto a three-strand
drag-chain conveyor which indexes them through the loader platform area.
Once loaded, the racks move along on the conveyor to the outfeed
section. Here, they are again transferred at a right angle -- this time
to two parallel lines of three-strand drag-chain outfeed conveyor for
transport to the holding position.
According to Chuck Askew, the new system offers some distinct
improvements when compared with the original approach. "Dual infeed
and dual outfeed lines give us a great deal of flexibility in
handling the racks," notes Askew. "Now we can tailor the
operation of the infeed and outfeed lines to match the needs of the
employees who work in the loader platform area."
In addition to greater materials handling flexibility, the new system
has substantially improved cycle times. Previously, it took
approximately 30 seconds to cycle a rack all the way through the system;
now the time required is in the order of 7 to 8 seconds. The result is a
system output that typically averages two fully loaded racks every 1.5
minutes.
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