Reliance Electric (Greenville, SC) is required by government regulation to have cradle-to-grave traceability for every electric motor it produces. It also competes in an increasingly global marketplace where the quality of its products is central to success against producers in other low-cost countries. In both of these areas, the company has made great strides by implementing an industrial RFID system to track parts and monitor its manufacturing processes.
Prior to going with a full-blown RFID system, the plant tried a host of other identification technologies, ranging from paper-based systems to bar codes. Inevitably, these approaches fell short of the company's needs. In the end, Reliance Electric went with a network based on passive HMS150 RFID tags from Escort Memory Systems (Scotts Valley, CA).
In operation, the tags, which function at 13.56 megahertz and have 712 bytes of read-write memory, are mounted in the base of each motor manufacturing pallet. As the pallets enter the manufacturing cycle, an operator writes a unique identification code to each tag using an HMS827 reader-writer unit, also from Escort Memory System. The tag identity is then forwarded via a CM81 communications interface module to a PLC running DeviceNet. Additional HMS827 reader-writers installed at each processing station automatically notify the manufacturing host when a pallet and motor arrive for processing.
Throughout, Reliance Electric's work-in-process (WIP) system sends instructions to tools and operators, holding the pallets at each successive station until the WIP system can confirm that processing is complete and all parameters are within specification.
Process data from each step is recorded into the WIP system database, where it is cataloged and stored with the serial number for permanent retention. The pallets are recycled after each use, with each pallet going through the manufacturing line approximately five times per day.
In all, there are some 30 manufacturing steps required to build each motor. These often vary, because Reliance Electric builds a range of motors on a single line. With so many steps, an error rate of as little as 1 percent at each step can result in a 26 percent scrap-rework rate. However, with the help of its RFID system, Reliance Electrics has kept the error rate below 0.1 percent.
For more information on RFID systems, call 800-626-3993 or visit www.ems-rfid.com.