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Six Sigma and the Single Tag
How do you achieve flawless read performance from your RFID system? By making sure it interrogates only one tag at a time.
Case Study 1: A number of items (with tags) are on a shelf, and you want to do an inventory.
If you merely want to scan the goods as a bulk audit, then you can sweep the reader in the area of the products and record the tags. This method is good only for a general information record. You have no certainty that you have read all tags and should not assume you have. To read the items reliably, you must assure that the RF field includes only the number of items you know to be in the field (be careful, though—if you cannot see a field and merely aim it at a tag does not preclude reading its neighbor). In this case, you may sweep the tags at full power so the interrogator can get a general idea, and then at a lower power, operating closer to the items of tags, so that the interrogator can read them individually.
So why is this better than bar codes? Time-and-motion studies will show it to be significantly faster because you do not actually need to find the tag and observe it visually.
Case Study 2: You have an over-the-belt situation and need to read a variety of shapes reliably at blazing speed, and also do sortation.
Sounds hard—even impossible, right? Well, you have two choices. You can either add varieties of readers and bells and whistles and still fail, or you can apply singulation. The latter is actually easier than you might think because you, the person concerned with this requirement, are already an expert in all the other necessary skills. Moreover, you already know everything about belts and motors, rollers and sorters, chutes and sensors. What a perfect candidate to apply singulation to RFID. The reward for using singulation is that RFID, coupled with the other normal triggers and sensors on the line, will provide Six Sigma results and increased opportunities for automation beyond what a bar code ever could. In the end, you may still have multiple RFID readers, but each will have Six Sigma reliability.
Case Study 3: You have a mailbag or carton filled with tagged items, and you need to know its contents.
In this application, you can be certain of 100 percent of the contents only when the container is being filled or emptied (singulation). You can always scan the closed bag or container—and even rotate it in the field to maximize the reading—but you will never be positive of the contents until they are singulated. If bulk scanning is adequate, then the only issue is that you should not base transactions on that reading.
"Those were crummy examples," you may be thinking. If so, then you are probably the type who insists on having your cake and eating it, too. You maintain that the penny tag will allow you to find the stick of chewing gum in the department store at will, via the Internet or even from your cell phone. If this describes you, then I apologize for wasting your time, but I do feel your delusions have (or will) cost you far more than the time spent reading this article.
Pat King is founder of Technologies ROI LLC, consulting within the supply chain industry. He has more than 20 patents in the fields of auto identification, RFID, imaging, lasers and printing.
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