Automated picking: Grocery giant Kroger changes the distribution game
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Automated picking: Grocery giant Kroger changes the distribution game

Automated picking: Grocery giant Kroger changes the distribution game

:: 08 October, 2009

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Kroger is building store-ready mixed pallets in an automated environment that streamlines processes in the DC and in the store.
By Bob Trebilcock, Executive Editor -- Modern Materials Handling, 10/7/2009
In the not so distant past, most grocery distribution centers made due with labor intensive, traditional materials handling technologies and processes. Pallets were moved by lift trucks and stored in racks. Mixed pallets were built the old fashioned way, with manual labor.

About eight years ago, The Kroger Company set out to play the distribution game by a new set of rules. Working with a systems integrator (Witron Integrated Logistics Corp., 847-385-6113,, the grocer created a new design to automate its grocery distribution centers. The end result was a system that can receive and putaway full pallets, then break them down and rebuild them into store-ready mixed pallets that are aisle-aligned. That means the cartons are loaded on a pallet in the sequence they'll be put away on the shelves in a specific aisle, with the top layers at one end, the middle layers in the middle of the aisle, and the bottom layer at the other end. But, the system also understands constraints like crushability so that it doesn't stack cans of soup on top of Japanese noodles on the pallet.

It all happens with almost no human intervention: Operators typically touch a product once when lift truck operators unload pallets at the receiving dock and once again when they are loaded at the shipping dock for delivery to Kroger's stores.From the supplier to the store, pallets are only touched twice in the Kroger facility: Once when a pallet is unloaded from an inbound trailer by a lift truck operator at the receiving dock and once again when it's loaded by a lift truck operator onto an outbound trailer at the shipping dock. In between, automation is in control.

From the receiving dock to the shipping dock, here’s how it works.
In the receiving area, a lift truck driver unloads a trailer and drops the pallets onto an induction conveyor where a fixed bar code scanner reads a label on the load. The warehouse management system determines whether that product is needed now in the mini-load automated storage and retrieval system (AS/RS) to fill an order or whether it can go into reserve storage in the unit-load AS/RS. Product that is needed now is delivered by conveyor to a depalletizer. Product that is going into reserve storage is sent to a pallet exchange machine where it will be transferred from a shipping pallet onto a permanent storage pallet.

Pallets going into reserve storage in the AS/RS are sent by conveyor to a mezzanine level where another conveyor delivers them to a pick up and drop off area. After the warehouse control system (WCS) determines the best storage location to maximize the cube of the AS/RS, a transfer car delivers the pallets to one of the 10 cranes that will pick up the load and put it away. It's now available to promise. Pallets with product needed now to fill an order are conveyed to a depalletizing area. There, an elevator raises the pallet to a mezzanine level where a depalletizing head removes and places a layer of cartons onto a descrambling conveyor. The conveyor orients the cartons into a single file and loads them on a tray appropriate for that SKU. The tray then travels through a matrix—or super highway—of conveyors that routes the tray to the right mini-load crane for that product. Depending on the size of the tray, the crane puts away either two or four trays at a time. The trays will remain in the system for no more than three days before they're retrieved for an order.

As product is pulled from the mini-load for orders, it will be replenished from the AS/RS using the same putaway process described above: Pallets are pulled from the AS/RS and sent by conveyor to the depalletizing area; from there cartons are placed on trays and putaway in the mini-load system.

Picking and packing
The facility is engaged in order fulfillment for as many as 22 hours a day. In general, orders are pulled from the mini-load system, palletized and loaded on a truck within five to seven hours after being received into the order management system. When an order drops into the facility, the WCS calculates which trays are going to be needed to build every pallet in that order and begins to pull the trays from the mini-load. They are delivered to a smaller mini-load unit that serves as buffer storage. The trays are loaded into the smaller mini-load, which then delivers them in the sequence they will be loaded onto the pallet to a short conveyor loop. The trays are then delivered to one of several palletizers. There, a case is lifted off the tray and placed on a staging area. A series of pusher arms position the carton on the right spot on the pallet. Once a pallet is built, it travels by conveyor to one of two automatic stretch wrappers.

Once the pallet is wrapped, it's placed on a takeaway pallet conveyor and sent to an automatic labeling station where a bar code label is applied. The label includes the aisle location in the shipping area as well as the store label information. The pallet is then conveyed to the right outbound station where a lift truck operator scans it and loads it directly on a trailer.

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