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Assembly in Action: Self-Propelled Conveyor Uses RFID

Hexcel Corp. (Stamford, CT) manufactures the honeycomb insert that goes inside the hard tonneau covers found on Chevrolet Avalanche trucks. Due to the size of the tonneau covers, a traditional conveyor system would be too costly and cumbersome for transporting the covers throughout the assembly process. The company contacted Ward Systems Inc. (Grass Valley, CA), a manufacturer of robotic and automated systems. Ward likes to "think outside the box," and this is exactly the approach Ward took when it installed the PowerPallet conveyor system at Hexcel Corp.

The system consists of motorized transport pallets and an inert conveyor. The PowerPallets act like miniature automated guided vehicles captured in tracks that guide them while they are traveling. They can accelerate and decelerate, providing a faster yet softer conveyance of products.

All the controls are located within the pallet. The large control cabinets and associated conduits that are usually necessary to wire all the motors, valves, photo eyes and proximity detectors to a central control point are not needed. Software is easy to develop, because the pallets provide the timing and control functions necessary for basic movement within the system. Simple destination commands are all that a PowerPallet needs to automatically move to any location within the system. It uses radio frequency identification (RFID) products to navigate freely throughout the system.

When Ward went searching for the right RFID products for its conveyor, ease of use; resistance to dirt, oil and dust; and fast tag-reading times were must-have qualities. After comparing RFID products, Ward chose Escort Memory Systems' (EMSScotts Valley, CA) RFID technology.

EMS's HMS827 Series passive readers and writers are each mounted on a pallet. The HMS125 passive tags are mounted along the various intersections of the tracks. A PowerPallet can travel through many intersections before finding the one it is supposed to stop at. While traveling through the system, the HMS827 antenna mounted on the pallet reads the tags on the line, looking for a specific intersection. Each intersection has five RFID tags associated with it. The tag on the intersection is programmed with the exact X and Y address of that intersection. The other four HMS125 tags around the intersection are programmed with approach information that the PowerPallet uses to slow its speed when approaching the correct intersection. These tags also report when a pallet exits an intersection, so the main controller knows the intersection is clear for other PowerPallets.

"The operational efficiency at Hexcel Corp. was dramatically improved after the implementation of the PowerPallets system. To successfully implement the technology, we needed an RFID product with fast, accurate reading speeds. Without that, our system would be limited to slow speeds. The pallets would not be able to successfully find their destinations with reliability. After searching for the best RFID solution, we realized that EMS was the best," says Glen Ward, president of Ward Systems, Inc.

For more information about RFID, call 831-438-7000, visit www.ems-rfid.com or Reply 2.

For more information about PowerPallet, call 800-458-6458, visit www.wardventures.com or Reply 3.

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