Specifically, the existing system was limited by the fact that it could only process 40 bytes of data per tag. It also had a maximum operating temperature of 140 F, which meant it couldn't be used in the facility's 390 F ovens.
Maximum write cycles, or the life of the tags, were another concern. The existing tags had a life of only 5,000 write cycles, which was totally inadequate for Toyota's massive level of production. Finally, Toyota wanted a new set of tags that would be both compact, and yet tough enough to stand up to the dirt, oil and physical abuse that are a natural part of heavy manufacturing.
Ultimately, Toyota decided to go with LRP250HT high-temperature RFID tags from Escort Memory Systems (EMS, Scotts Valley, CA): tags that offer 48 bytes of memory, a lifetime of 100,000 read-write cycles, and are capable of surviving prolonged exposure to temperatures in excess of 200 F. Because the metal dollies that Toyota uses to transport work-in-progress interfere with their range, EMS mounted the tags using a small metal bracket with a ceramic spacer.
As part of the upgrade, Toyota wanted the changeover to be entirely seamless. At the time, the company was also ramping up production of its latest Corolla and Avensis models, and managers didn't want production to fall behind schedule. Among other things, they didn't want to have to transition the entire system all at once. Such an approach would mean that unforeseen technical problems could cause a catastrophic work stoppage.
As a result, Toyota, EMS and systems integrator Datascan Systems Ltd. (Bromsgrove, England) conducted the changeover by gradually switching out the antennas and tag stations one at a time. For a while, this meant the plant was using the new and old systems simultaneously, thereby verifying that the new tags were being written with the correct information. As an added benefit, this approach meant engineers could do any necessary debugging without negatively impacting productivity.
As part of its new system, Toyota also implemented a series of LRP820-04 Reader-Writer Conveyer antennas. These antennas provide a 6-inch range and can fit into tight areas surrounding or within a conveyer line.
Mounting the antenna required some creative thinking, because space underneath the dollies was limited. In the end, Toyota installed a series of brackets to raise the antennas approximately 2 to 3 inches off of the metal floor. These brackets serve to reduce interference and hold each antenna at an angle that lines it up adequately with the tags.
In total, Toyota is using 39 separate LRP820-04 controllers and antennas. Nearly two-dozen CM52 interface modules, also from EMS, are used to link the system of readers to a battery of operating PLCs.
Finally, Toyota is using a set of EMS-supplied handheld readers near the beginning of the production line to program attributes like model and color information onto each vehicle's tag. This information is then accessed and updated again at each subsequent station as the vehicle and its tagged dolly pass through.
For more information on RFID, call 831-438-7000, visitwww.ems-rfid.comoreInquiry 1.
