When I think of a warehouse, I visualize a facility with racks. But in industries that sell commodities (e.g. fresh produce), “bulk” warehouses without racking are more prevalent. What you are likely to see in these warehouses are painted lines on the floor where pallets are stacked. Oftentimes, a worker has to move a stack of pallets out of the way in order to select the pallet(s) containing the products that need to be shipped.
Bulk warehouses present problems for Warehouse Management Systems. While a WMS location code can theoretically correspond to a painted location on the floor, and the layout location logic embedded in the WMS can encompass stacked pallets, enforcing process discipline is more difficult in a bulk warehouse. In a traditional warehouse, a worker goes to a location and scans the barcode at the slot, and so the WMS knows that the worker has picked the right pallet. The process is enforced.
In a bulk warehouse, the worker goes to a location in the warehouse containing several stacks of pallets. He moves a few stacks out of the way, gets to the correct stack, and scans the barcode on the pallet(s). The WMS then knows that the picker has retrieved the correct pallet. The worker is then supposed to put the pallets that he moved out of the way back in the precise order they were originally. The WMS assumes this task is performed correctly, but what if the worker puts the stacks back incorrectly? This is why put-away mistakes are far greater in bulk warehouses.
This is the problem that a relatively new company called Sky-Trax solves with a Real Time Location System (RTLS). This RTLS is based on optical technologies and can operate indoors. While there are RTLS solutions for the warehouse yard, those solutions typically use different technologies that are not particularly well suited for indoor environments.
Here is how the system works. An optical position sensor on top of the forklift reads 2D tags that are strung in a grid pattern on the ceiling. These 2D ceiling barcode markers are mapped to a facility CAD drawing. The combination of ceiling reads and a predefined grid allows the RTLS middleware to know where the lift trucks are within the warehouse at any instant. RFID readers, or the combination of optical readers and lift height sensors, can be used to check whether the right pallet has been selected. In this way, accurate inventory/location data can be fed to a Warehouse Management System (WMS).
Sky-Trax also offers some interesting analytics. For example, they have analytics that can tell a manager the percentage of time a forklift is moving with a pallet, sitting still, or moving without a pallet. These metrics can be used to drive process improvements that allow for better asset utilization.
I talked to a consultant in New Zealand that has installed this solution, using RFID for the pallet reads, in a refrigerated kiwi warehouse. It turns out that there are far more attributes associated with kiwis (e.g., size, freshness, color, and many more), and refrigerated kiwi warehouses are far more complex, than I ever could have imagined. It was the perfect illustration of why there will always be a need for custom warehouse solutions.
Anyway, while there were several payback buckets associated with the project, the key source of savings was based on productivity improvements. These productivity improvements were associated not with moving through a warehouse more efficiently, but with avoiding all the work associated with trying to find a pallet that was improperly put away. The kiwi distributor was able to achieve a payback of less than one year with this technology.