The Ford Motor Co.'s facility in Cuautitlan, Mexico, produces 300,000 to 400,000 cars and trucks each year. Ford builds vehicles in Cuautitlan using a method of just-in-time suppliers with vendors supplying parts on an as-needed basis. Because of this method, it's crucial that inventory and tracking in the plant be precise and closely monitored.

However, keeping track of inventory and production automation in a large facility can be a daunting task. Before Escort Memory Systems (EMS, Scotts Valley, CA) was called in, Ford used a manual coding system to track auto and truck frames as they went through the final assembly, paint and body shop areas of the production line. Unfortunately, this manual system was very ineffective due to frequent error and costs associated with production oversights. Paper identification sheets, used to track the vehicles, were being lost, switched or ruined, making quality control difficult.

Because it had worked at Cuautitlan in the past on identification routing solutions, Ford contacted EMS for help in eliminating the plant's paper-based system. Ford also used CAPTA, a Mexico-based company with experience in radio frequency identification (RFID) projects, to integrate the technology.

Using RFID technology, a tag could be secured to a vehicle skid, and then custom programmed with a serial number that would be referenced through Ford's operating system. This serial number can indicate what has been done to each vehicle, as well as what still needs to be completed further along the production line.

These tags also had to withstand extreme temperatures inside enamel paint ovens at temperatures up to 220 °C. EMS' LRP250HT tags were subsequently chosen because they can function in hot settings, and because their 48-byte memory and 1,200 bytes/sec transfer rate could easily handle Ford's 23-digit reference serial numbers and production rates.

Meanwhile, mounting the tags required a unique solution. Mounting them directly on metal vehicle bodies would have compromised their range, while accompanying interference would hinder the tags' ability to function at normal levels.

CAPTA's solution involved constructing a mounting bracket that attaches the tag to the metal skid carrying the auto bodies. This bracket, constructed of Teflon, creates a non-metal border for the tags, creating optimal range and optimum read/write conditions. Tags are mounted, so they can be reattached, rewritten and reused after a vehicle is finished.

To install antennae for reading the tags, EMS picked its LRP-08 antenna, which met required range specifications. Twenty antennas-five in body production, 12 in the painting process, and three in final assembly-were set into the floor of the production line in a nylon explosion-proof enclosure, and wired using RS-485 transmission protocol. As each skid passes over an antenna in the conveyer belt, contents of the tags are sent to the EMS' LRP820 readers, which were interfaced to Ford's operating system.

As a vehicle passes through the different stages of production, different parts of the 22- to 23-digit serial number are referenced, indicating what needs to be done at each station. This is one of the biggest benefits of RFID. Where the former manual coding system required each identification sheet be manually updated at every turn in the production line, RFID allows updates to be written to the tag, so that it is constantly being updated without risk of operator error.

Ford reports that it has found EMS' products to be extremely useful and effective in this application. Ford has established an accurate and efficient method for routing and identification, and evolved automated production capabilities to relay more information than previously thought possible.

For more information on Escort Memory Systems, visit www.escort-rfid.com.

- Dick Johnson, senior editor; djohnson@reedbusiness.com