A number of manufacturers—especially those in the aerospace, automotive, sporting-goods and wind-energy industries—make products that contain composite materials consisting of epoxy or other polymer impregnated with carbon, glass, Kevlar or other types of fibers. Some of these manufacturers purchase premade composite material, in pre-impregnated form (prepreg). Prepreg is a temperature-sensitive material, and companies that manufacture and sell prepreg must store the composite materials at 0 degrees Celsius (32 degrees Fahrenheit) or colder to prolong their shelf life. Nonetheless, prepreg providers must warm the material slightly before they can cut off pieces requested by their customers. Often prepreg can sustain only a limited amount of “out time”—that is, time spent outside cold storage. A prepreg product’s shelf life is reduced anytime it is taken out of the cooling environment. Material may have a total shelf life of 64 hours outside of the cooler, and cumulative out-time has to be calculated each time the product is removed.
DeltaTrak manufactures and sells portable test instruments and software that monitor and record environmental conditions such as temperature. When, in August of 2010, an aerospace-materials manufacturer, which has asked to be unnamed, came to DeltaTrak seeking a technology solution, its managers were hoping for technology that would track temperatures, such as a data logger or RFID, recalls Steve Russell, DeltaTrak’s North American sales director. The aerospace product company had been using paper and pen to manage out-time tracking, a process that was labor intensive and prone to error if someone failed to record a time, wrote it incorrectly, or misplaced the paper.
DeltaTrak proposed a system that provided an automated solution that would not only record the amount of time each roll spends outside a freezer and how warm it got during that time, but send that data and alerts in real time to the relevant parties when the maximum limit for the product’s exposure to temperatures warmer than 0 degrees Celsius was approaching.
DeltaTrak designed a solution that uses ZigBee-based RFID loggers, called FlashLink RF, six months ago. The initial deployment consists of approximately a dozen RFID loggers, with each tag placed inside a plastic sleeve that was adhered to the composite roll. The aerospace-materials manufacturer installed five DeltaTrak readers, known as repeaters, which receive 2.4 GHz signals transmitted by tags up to 25 meters away. The repeaters in turn form a mesh network, transmitting data via the ZigBee protocol to each other and to a gateway, which is another repeater device that receives the data and forwards it to the software residing, in this case, on a stand-alone laptop computer (the system software can reside on the user’s back-end system or on a hosted Web-based server).To boost the signal between the gateway and the laptop, Charles Craig, DeltaTrak’s IT technical support manager, developed a Bluetooth connection that would allow the gateway to send data up to 300 feet to the laptop. The significance of the Bluetooth booster is two-fold: allowing the laptop computer to remain in an office rather than in a manufacturing area, where it could sustain damage, and also allows the gateway to be positioned in the center of the coverage area, to maximize the amount of transmissions received from the five repeaters.
When the tags, affixed to the composite rolls, are in the freezer, they remain dormant. When they are removed, they detect a change in the ambient temperature and begin to transmit the measured temperature at a rate of once per minute to the repeaters. The repeaters receive that tag data including the unique ID number that is linked to the specific roll of composite. They then forward that data to the nearest repeater or gateway, and the gateway then sends the data to the back-end software via a Bluetooth connection. The FlashLink software stores the temperature data and links the time with the composite roll’s previous out-time data. Rolls can be out of freezing for a variety of time periods based on the materials it is composed of. Some can sustain 64 hours, others less. These requirements are also stored in the system software for each roll’s tag ID. When the maximum time is approaching (such as at 50 hours for a 64-hour maximum roll) an e-mail or text message is sent to the authorized recipient who can then ensure the roll is returned to the freezer soon and consumed before the limit is reached. Once the limit is in fact reached, the roll must be eventually scrapped or retested to establish if there is any additional shelf life.
Manufacturers of raw materials also ship their products with specific temperature requirements, but out-time tracking for these materials begins at the composite manufacturing plant. With DeltaTrak’s system, the company can not only automatically track the temperature conditions of its product, it also hopes to share that data with its customers and will recommend that its suppliers use the system to track the temperatures of raw materials it uses to manufacture its composite rolls. Currently, Russell says, the software is being adjusted to calculate the maximum out-time for products based on the kinds of raw materials that are received at the site.
DeltaTrak and the aerospace product company are also planning to incorporate real-time location system (RTLS) functionality into the FlashLink system, using triangulation of the repeaters to determine if the rolls are in cutting rooms, or staging area, for example, which would allow management better understanding of where bottlenecks may occur based on historical data as to how long a roll is in a specific place, or to find a roll in real-time if an alert is sent.
With the system, the user can also provide the data to auditing bodies such as the Nadcap Performance Review Institute or customers such as aerospace companies that require a record as to how out-time sensitive composite materials are outside of freezers. The first Nadcap audit scheduled since the system was installed is expected soon, Russell says.
Although the FlashLink RF Wireless System was custom-designed for the aerospace product company, DeltaTrak says the system is now available commercially. The technology could support 100 tags for each repeater, Russell says, making it scalable to much larger deployments of other time and temperature sensitive materials. He predicts the technology could be in great demand as the prepreg composite market expands in the automotive industry, as demand increases for lighter-weight, more energy-efficient vehicles.