40 n WAREHOUSE AUTOMATION January 2025 www.drivesncontrols.com Can you track warehouse stock in real time? Warehouse space is expensive, as is the stock – even more so when it gets moved and you lose track of it. Hence any way of keeping track of this stock reliably in real time is a tremendous benefit. The simplest warehouses often use shelf locations arranged in alphanumeric order, with one location for each product. This is very inefficient in terms of the space, as a location is required regardless of whether there is currently any stock in it or not. Gaps must be left for new products to be accommodated between current locations, or for larger quantities of the items to fit in the correct location. This system doesn’t require any form of tracking beyond goods in and goods out, but is the most prone to errors and misplaced items. One improvement is to use numbered locations which get filled based on quantity and product dimensions, not part numbers. This keeps track of what product is in which location and directs personnel to place items in a location or pick from a location. This uses space more efficiently, because any location can be used by any product. But it still relies on a person using the correct location, and not moving anything. Often these systems are combined with barcoding, with every product carrying a barcode and personnel scanning the barcode when they pick or place the item. This confirms that the correct item has been selected, but is still vulnerable to items being moved or removed without the system’s instruction. Errors can also occur when the same item is scanned multiple times. And barcodes can only be read at close range, one at a time and in direct line-of-sight, which limits their use where large quantities are involved. Playing tag RFID tags can be read from a greater distance, do not need line-of-sight, and multiple tags can be read at the same time. This allows a whole pallet of goods to be scanned without removing items from their containers. There are standards for the data content of RFID tags defining products, shipments and assets, allowing shipments from multiple suppliers to be received without issue. RFID tags are more robust and reliable than barcodes but usually cost more. Bulk quantities of low-value items are often identified with a single RFID tag. In busy shipping areas, pallets of goods with RFID tags can pass readers in many directions at the same time. The inventory system must be able to distinguish between them, identifying the tags that it should be reading and ignoring any others, including stray tags that may have become stuck to a forklift. RFID tags need to be within a few metres of the reader and installing enough read heads to cover every location in a warehouse is not normally practical. RFID systems still rely on operators placing the items in the location they were directed to, and not moving one item to create space for another. Tracking items accurately around warehouses in real time has big potential benefits in terms of saving time and money, and avoiding errors. Steiner Roberts, business development manager for systems at Turck Banner in the UK, outlines some of the technologies available, and how combining two of them may be the ultimate answer. Items can be tracked accurately around warehouses in real time by combining RFID tags with radio- or Bluetooth-based real-time location systems
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