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Radio Shack sortation system:
Flowcon
provided the sortation control for the force feed warehouse in Ft. Worth
Texas. We automatically routed 30-40 boxes per minute to 150 storage queues, then
released them in groups for shipping by zones to stores nationwide. |
Box separator and scanner
Box
separation allows arms to divert boxes as they route through the system. Once scanned, a
box's exact location is remembered by the system at all times, until it is released at the
shipping dock. |
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Diverted to three levels
The boxes
divert to one of three levels. This calls for extreme accuracy as the divert contact point
with the box is typically within one inch, on a line that is moving at 300 feet per
minute. |
Level controls
Each level
had a 220' belt, 50 diverters and 50 storage lines. The location of every box was known
within 1" by tracking the belt travel with rotational encoders, and by timing box
arrivals with photo eyes. Even a slight variation in box strikes could cause a missed
divert, or a serious belt jam. |
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Maximum load capabilities
At 40 boxes
per minute and up to three minutes to destination, a maximum load scenario requires
perfect tracking of up to 120 boxes at any moment in time. The system was also able
to handle the worst case scenario -- 153 diverts at the same time. |
Ceiling height limitations
The control
system functioned as designed for many years. As seen in this picture, the ceiling height
excessively limited the amount of slope on the queues, and thus boxes did not always
release without manual intervention, which became a human liability issue. |
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Takeaway belts
Boxes in the
queues were released to these three takeaway belts, and automatically grouped by zipcode
to reduce postal rates. Boxes were conveyed to the shipping dock, where they were staged
and loaded into semi-trailers. |
Control room
The control
room is in the middle-left of this picture. The Radio Shack computer displayed all
activity on three screens, one per level. |
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Solid state control relays
A high speed
data cable allowed for micro-second response times. There were 276 AC input relays, and
392 AC outputs for a total AC relay count of 668. Additional high-speed DC relays in the
control room, tracked the four encoded belts, plus there were a few analog controls for
special functions. |
Control computer system
All box
movement was dynamically displayed on the screen for the level it occupied. Operators
could search and display shipment locations. Sorting and staging were run as two separate
functions, and ran independently of each other from the same computer and same keyboard. |
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