USPS turns to automation for seasonal crush

A temporary handling system with fixed-position scanners gets the job done.

By Staff -- Modern Materials Handling, 10/2/2005

Every year during the holiday season, the Seattle United States Postal Service (USPS) processing center receives so many over-sized parcels it must lease 150,000 square feet of warehouse space with 30 dock doors to process them.

In the past, the facility used a manual sortation system, but increasing volumes demanded a more efficient solution. USPS was interested in an automated system with high-speed bar code scanning that was able to accommodate the volumes of the holiday season.

When the USPS opened its holiday annex during the most recent holiday season, that system was in place. It was fully automated complete with hundreds of feet of roller conveyor lines, eight weigh scale stations, and two network hubs connected to the main facility via a wireless network. The entire system was set up in 3 weeks and broken down in just a few days after the season had passed.

With the new system, large packages are unloaded and placed on a conveyor and routed to one of eight weigh stations. The bar code on the package is scanned by a bar code reader with the data sent to a programmable logic controller (PLC), where it is buffered and held until the scale determines the weight of the package. Once the weight is logged and matched with the bar code data, the data is sent to a network hub connected to the wireless network.

The network hub then determines the most effective delivery route, prints the appropriate label and an associate applies it.

The system features two RS 485 data ports, allowing the PLC to receive data from both the bar code scanner and the scale at the same time. Since nearly 25% of the packages arrive at the facility without a bar code, a keyboard was connected to the same data port as the scanner by way of a keyboard wedge, enabling the operator to key in the zip code of packages missing bar codes. The bar code readers were selected for the application for their programmable read range and ability to consistently read poor quality, low contrast bar codes.

The automated system immediately improved production efficiency and shipping accuracy, handling three times the normal volume while still reducing cycle time and the number of people required to perform operations. They met all of their carrier deadlines ahead of schedule and were able to dispatch early each night during the holiday season, something they had never been able to accomplish with the previous manual system.