RFID impacts automation

Related reading
For more on RFID from Control Engineering , search on RFID at top of www.controleng.com or click into the following:

• RFID: ROI more than 2 years; high-speed bar-code matching

• RFID helps with tires, food and drug, automotive applications; 6-point RFID roadmap

• PLC function block code aids RFID compliance

Lower-cost RFID tags are a new opportunity in manufacturing that will have a major impact on manufacturing IT systems. Essentially RFID tags are radio frequency bar codes implemented with inexpensive semiconductor chips and antennas. RFID tags can be read without having to physically view the tag, making them much more automation friendly.

There has been a lot of press on RFID tag prices, possible uses, and advantages to the supply chain, but not much has been written about their impact on plant floor systems and connection to business systems. RFID tags have some unique differences from bar codes, but the primary difference is that most low-cost RFID tags are ‘read only.’ Unlike bar codes that can be printed on demand with the exact information required, RFID tags are usually purchased pre-configured. This may seem like a minor detail, but it has major implications for the amount of information exchanged between shop floor manufacturing execution systems (MES) and high-level planning systems (ERP).

Most inexpensive RFID tags follow the Electronic Product Code standard and provide 96 bits of information. The 96 bits are split into 8 bits for a header (defining the partitioning scheme for the rest of the bits), 28 bits to identify the manufacturer, 24 bits to identify the product type (SKU code), and 36 bits for the RFID serial number. What the codes do not contain is the lot or sublot identification of the product.

Usually RFID tags are applied to the product late in the packaging stage, either added to the product or applied to the carton or container. Because RFID tags are pre-configured, the lot and sublot information can be associated only with the RFID serial number late in the production process. Assignment of RFID serial numbers prior to packaging will probably be uneconomical, if not impossible. Unless care is taken, there may be no guarantee that applied RFID serial numbers are contiguous, that all applied tags actually work, and that defective product is not removed later (such as dropped or damaged cases). Information collected in the packaging step must be combined with the shop floor information about lots, sublots, or batches, and then sent to the company’s supply chain or ERP system.

Today, most plant floor systems return only summarized information to ERP systems, such as how much product was produced and the product lot numbers. For example, a pharmaceutical manufacturer may report only one set of information about a product lot, indicating the materials used, the amount produced, and the lot identification. If, instead, each container has a separate ID, then thousands of identification records may need to be exchanged for each lot produced.

Most plant floor systems do not even maintain the required information. Many will have to be expanded to record and track product containers through the final production process. The amount of information that will need to be exchanged with the ERP system is too great for manual exchange, so automated integration between shop floor systems and ERP systems will be required. The method for information exchange will also have to be robust and operate without guaranteed communication access. Many plants are not even on the same continent as the ERP system and will have many occasions when they cannot communicate. This will require a new class of manufacturing IT integration architectures that are asynchronous and loosely coupled, based on message queuing systems with guaranteed delivery.

Implementing RFIDs will require new or expanded manufacturing IT systems. The systems will need to track and record every container produced (or every one labeled), and the systems must have reliable links to corporate business systems. These little RFID tags are going to have a big impact on automation systems and manufacturing IT budgets.

Read this column at www.controleng.com , Archives, January 2005, for links to related Control Engineering coverage.

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