ABB containerisation system gives US postal service the vital competitive edge

Citation

(2002), "ABB containerisation system gives US postal service the vital competitive edge", Industrial Robot, Vol. 29 No. 5. https://doi.org/10.1108/ir.2002.04929eaf.008

ABB containerisation system gives US postal service the vital competitive edge

ABB containerisation system gives US postal service the vital competitive edge

Keywords: Robots, Handling

Developed specifically for the US Postal Service by ABB Automation, a highly sophisticated robot containerisation system (RCS) is bringing unprecedented levels of speed, accuracy, efficiency and productivity to the process of sorting and containerizing mail. The system's combination of performance and reliability make its installation and attractive and viable proposition for postal services throughout the world, including the UK.

Today, at the US Postal Service's Chicago Metro Surface Hub (CMSH) just west of O'Hare International Airport in Elk Grove Village, Illinois, four high-throughput ABB RCS systems are being put to the test under some of the most demanding mail processing conditions (see Plate 7).

Nearly 465,000sq.ft in size, the massive CMSH processes incoming and outgoing mail for postal delivery centers throughout the metropolitan Chicago area. Approximately 650 people work here over three shifts around the clock, receiving and dispatching mail through 70 loading dock doors.

Processing mail at the CMSH is a highly automated operation. The facility features seven bundle-sorter machines, two flat sorter machines and six robotic mail-sorting systems including the four ABB RCS double-gantry robot systems installed in the summer of 2000.

Plate 7 The massive CMSH processes incoming and outgoing mail for postal delivery centres in Chicago. ABB's robotic containerisation system has brought a great increase in productivity

The throughput of the ABB RCS systems has been excellent. "Each of our RCS systems is utilized for specific purposes and destinations," explains CMSH Maintenance Manager Surjit Grewal. "Our most heavily used RCS is utilized primarily for sorting incoming mail. It handles, on a average, 80,000 to 100,000 mail trays per month."

The other three RCS systems, working from different sort plans, each handle an average of 30,000 to 50,000 trays per month. During test runs, the four systems each demonstrated the capability to run over 600 trays per hour.

As the trays of mail are brought into the RCS by the in-feed conveyors, bar code reading stations scan the bar code on each tray for sorting purposes. The RCS control system then determines where each tray belongs in the sort scheme, and separates the trays accordingly between the two robotic sides of the system.

"The RCS system's accuracy in sorting has been perfect," Grewal notes. "It reads the bar code on the tray, and sorts it accurately."

The RCS, in fact is designed to virtually eliminate the possibility of mis-sorted trays. The bar code readers have a very wide field of view to maximize read rates and accuracy. They can also read labels in omni directions, no matter how a label is oriented on the tray.

"The scanners on the RCS are very reliable," Grewal adds. "That helps to reduce a lot of the problems with constant breakdowns and mis-sorted trays, which in turn helps to ensure the on-time dispatch of containerized mail."

The innovative double-gantry design of the RCS has been another big plus for the CMSH On each side of the RCS, an overhead, gantry-mounted robot retrieves trays from the in-feed conveyor and loads them into containers. Two robots each have a telescoping arm equipped with a mechanical gripper designed to handle all type of intermixed mail trays.

Each of these two robotic gantry sections is in turn divided into two zones. This allows one zone of the gantry to continue sorting operations while the other zone is undergoing cart exchange or maintenance.

"We like the fact that we can constantly work and continue to process mail even if one zone is disabled," Grewal says. "If the container in one zone is full, we can change it and the whole system will not stop. Three-quarters of the RCS will keep working.' 'That helps us with our run times and our throughput," he adds.

The two robots sort to either side of the conveyors, filling containers as the trays and tubs arrive. Here, the high levels of flexibility of the RCS are a key factor in its efficient performance. Uniquely designed robot grippers allow the RCS to handle mail trays that are sleeved or unsleeved, as well as open or topped mail tubs. Metal fingers on each gripper support trays from beneath for secure handling, and a containment plate on top holds mail in place on open trays. "The vacuum suction-type grippers on our other robots can only handle sleeved trays, and tubs," Grewal notes.

The RCS can also sort mail to a variety of containers, including general-purpose mail container (GPMCs), eastern regional mail containers (ERIVICs), and pallets. The robot automatically senses the container type and handles it appropriately (see Plate 8).

"Compared to our other mail-sorting robots, one of the biggest advantages of the ABB RCS system is its ability to sort mail to 24 different containers," says Grewal. "Our other robots can only sort to 12 containers."

The ABB robot's gripper senses and handles intermixed trays and tubs automatically with no changeover needed. The trays and tubs are handled just once to maximize efficiency. Top loading eliminates the need to orient containers into a specific position. With its robotic arm, the RCS can even determine the position of the shelf in a GPMC, automatically lower the shelf once the container is half full, and then finish loading the container.

Plate 8 The ABB robot automatically senses container type and handles it appropriately

For maximum packing efficiency, containers are filled to a specific height, rather than to a count of trays. When a container is completely filled, the operator requests and obtains access to that zone of the RCS. All operations in the zone come to halt, the gate is unlocked, and the operator enters the RCS.

Any incoming trays destined for the zone the operator has entered continue to recirculate on a looping conveyor until the operator removes the filled container and closes the gate. This recirculation prevents trays from blocking robot operations during container exchanges, to minimize downtime and maximize throughput.

All RCS functions are controlled through a convenient graphic user interface screen. This interface provides an easy-to-use visual representation of the system, showing the locations of containers and pallets. Sort schemes are easily created on the interface, and operators can obtain information on the system's overall status. "For our operators who are familiar with the system, I'd say that the RCS is relatively user-friendly," Grewal notes.

Among the many benefits robotic automation brings to mail sorting and containerizing, improved ergonomics is a key issue. By eliminating the manual lifting of heavy mail trays and tubs, robotic systems help to reduce workers' injuries and the associated costs.

With a footprint of just 9,000sq.ft including guarding, the compact, rectangular shape of the RCS helps to conserve floor space. It allows for ample room on the sides and ends for operator access and container removal.

The number of moving parts in the RCS has been minimized and proven components and technology have been used wherever possible. The result is a remarkably reliable system with high uptime and an expected MTBF (Mean Time Between Failures) of more than 50,000 hours.

For further information contact: David Marshall, ABB, Auriga House, Precedent Drive, Rooksley, Milton Keynes MK13 8PQ, UK. Tel: +44 (0) 1908 350300; Fax: +44 (0) 1908 350301; e-mail: david.marshall@gb.abb.com