RFID on the Production Line
Talk is cheap, but radio frequency identification (RFID) systems and tags are still relatively expensive. This is especially true if the tags are applied on a close to per-item basis and if they're not reused. So, when Wal-Mart told its top 100 suppliers in June 2003 that it wants RFID tags on all cases and pallets shipped to its distribution centers by January 2005, many started slapping, ship...
Control Engineering Staff
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Talk is cheap, but radio frequency identification (RFID) systems and tags are still relatively expensive. This is especially true if the tags are applied on a close to per-item basis and if they're not reused. So, when Wal-Mart told its top 100 suppliers in June 2003 that it wants RFID tags on all cases and pallets shipped to its distribution centers by January 2005, many started slapping, shipping, and seeking ways to increase return on investment (ROI) and reduce costs.
One of these top 100 suppliers is Wells' Dairy, which provides Wal-Mart with Blue Bunny ice cream and novelties. Wells' reports that it's the largest U.S. family-owned dairy, and that it operates the world's largest ice cream manufacturing facility, located in LeMars, IA, which can run up to 160 hours per week.
While many suppliers try to comply with new RFID rules by adding tags just before shipping, Wells' decided to seek benefits and savings by implementing its RFID system early in its manufacturing process. Brad Galles, Wells' process controls manager, began working with the dairy's automation supplier, Rockwell Automation, on a pilot project in mid-2004. Their in-house-developed solution uses Allen-Bradley 1756 EWEB modules for ControlLogix to process data from Alien Technology's RFID readers and 915-Mhz, 96-bit Squiggly tags (see illustration, at left).
These RFID tags are written onto by the antenna-reader, and then applied to each two-bucket case as it's wrapped, at 30 cases per minute. The tags are read again up to four times as the cases are quick-frozen and eventually shipped. The RFID system passes information back into Wells' control architecture and shares it across the firm's enterprise network. A typical slap-and-ship system would have forced Wells' to manually rewrap and re-palletize its cases, which would have increased labor costs, Galles explains.
'From the outset, we viewed the implementation of RFID technology as a catalyst for making process changes that improve business performance,' says Galles. 'Once the data is collected, it can be used to improve inventory tracking; automate many of our quality control and inventory processes; and simplify our data collecting processes.' Wells' adds its RFID system has freed up personnel; helped increase accuracy of freezer counts; decreased mis-shipped pallets; and minimized the need for manual reconciliation.
The dairy and Rockwell add many efficiencies provided by the RFID system are aided by the data processing capabilities that resides behind the tags. For example, each RFID tag at the dairy is linked to a database that holds the production attributes of each case of ice cream, including time produced, batch identification, and production line. This lets Wells' operators know precisely when each tag is applied, and from what batch the pallet originated.
In essence, the sophistication of an RFID tag's identification data can help physical status and environmental data in the user's database, certify that process changes have occurred or that tests have been passed, and enable decisions and actuations to improve quality even further.
'The value of RFID lies in its ability to add value by increasing plant-floor visibility, which it does by collecting data in a way that's compatible with equipment we already have,' says Galles. 'To achieve maximum value for investment, it was important for us to design the RFID system using the same ControlLogix platform used in our existing processes.'
Sure, RFID tags don't require line-of-sight, can handle more data, and are more robust than the ubiquitous and less-costly barcodes they're supposed to replace. And, RFID is less expensive than traditional radio transmitters and other wireless technologies.
Still, as presently applied, RFID is mostly used for identification, material handling, and other forms of documentation. This may satisfy recent Wal-Mart and U.S. Dept. of Defense (DoD) directives to install RFID systems, but it has also fueled tremendous hype, which is already being postponed and/or scaled back in the face of reported implementation hurdles and questionable ROI.
So, as usual, it's up to users to evaluate their applications, confirm their needs, learn about RFID capabilities and costs, and then decide if RFID is a worthwhile way to improve their efficiency, aid decision making, improve quality control, and increase productivity, or opt for a barcode, radio transmitter, or hardwired network is most appropriate.
'While a barcode is seen though the 'eyes' of a data collection system, an RFID tag is heard though its 'ears' and can be spoken to through its 'voice,' which is simply a better way to have control and visibility into the supply chain,' says Bill Arnold, of Omron Electronics LLC. 'While a barcode only has 14-16 digits, RFID allows 96 to 256 digits on each tag, which allows a level of uniqueness that can identify products down to the shift, machine, and operator that produced them.'
RFID tags can be read-only, write-once-read-many (WORM), read-write, passively read by an antenna/reader, or actively send signals, usually aided by a battery.
'RFID is essentially an automatic data collection technology, rather than a control technology, but it can be integrated into control systems because it can read and write to those systems,' adds ArnoldSo, while a barcode can help track an item, RFID can track and record events, parameters, and measurements. This ability to store data, survive harsh conditions, and be written to make RFID more powerful than barcodes and less costly than a radio transmitter. This means users can make decisions and actuate changes more quickly, such as finding an item faster if it doesn't pass certain test criteria.'
Omron's 125-MHz RFID tags and V700 RFID reader were recently combined with an Intermec barcode system, and installed by a system integrator, the SMS Group, to streamline automobile seat manufacturing and traceability at Indiana-based Total Interior Systems-America (TISA), which supplies minivan seats to Toyota's plant nearby. 'RFID tags were used to supplement the existing barcodes in this case. One didn't replace the other,' says Mike Deal, SMS' automation and data collection manager. 'The tags gave full traceability to TISA's just-in-time (JIT) and just-in-sequence (JIS) system, which pre-assigns the specifications and placement for each seat.'
Deal adds that TISA's conveyors are controlled by PLCs and SMS' customized Core middleware, which accesses tag data via Omron's reader. The middleware also can talk to TISA's PLCs and its ERP system. Because its tags are reused in what RFID integrators call a 'closed loop,' TISA's system enables continuous JIS verification, and reportedly achieved ROI in six months.
Omron reports that the RFID reader, software, and printer included in its newly released RFID kit can help users implement a manual, compliant RFID system for $12,000-$15,000, rather than the $200,000 that it says traditional systems typically cost.
Closed loop to open loop
Similar to traditional radio transmitters, RFID tags were historically brick-sized devices that cost about $100, usually monitored work in progress (WIP) in harsh industrial applications, and were more capable, such as having longer ranges. 'Historically, read-write data stored on RFID tags also allowed user to build machine that functioned as islands because the tags retained the recipes and other process data,' says Helge Hornis, Pepperl+Fuchs' intelligent systems manager. 'When the Internet and Ethernet began popping up, users started running applications with smaller memory tags, which were linked to central databases and enterprise systems.'
In a typical RFID scenario, the electromagnetic field of a reader/transceiver excites the circuitry of a tag, which produces enough power for data to be exchanged between them. The data can then be relayed though controllers, and onward to PLCs, PCs, and databases as needed.
Though they've shrunk to cookie-sized and smaller and their cost dropped to a few dollars or less over the years, these tags are still reused hundreds of times in closed-loop applications, diluting initial implementation costs. They're typically used to track big-ticket items, such as automobile chasses and components, which also helps make them economically worthwhile.
'Traditional RFID tags work almost like an extended hard drive, and users can read and write onto them all the data on the quality measures that need to be achieved,' says Alec Stuebler, Siemens Energy & Automation's business manager for factory automation sensors. 'For example, an RFID tag can help confirm that tools measuring torque during automotive assembly meet pre-defined measurements, and then allow components being assembled to move to the next step. Or a heat-resistant tag can help start a paint process, and then verify quality when it comes out of the 250 °C oven.'
Steubler adds that read ranges for RFID tags can vary from 2 mm for flush-mounted tags in tooling applications to 2.4 GHz tags that can read at 300 meters. Memory sizes can range from 96-112 bytes up to 64 Kbytes, though more memory may require added power, such as a battery, to keep that memory active and accessible.
RFID systems usually operate at three main frequencies: low frequency, which is below 1 MHz; high frequency, which is the 13.56-MHz universal frequency required worldwide for scientific instrumentation; and ultra-high frequency (UHF), which is over 800 Mhz. UHF allows longer range and is less costly, though it reportedly has some interference issues.
Siemens plans to introduce its Simatic RF 600 and Simatic RF 300 products in August 2005. Reportedly able to achieve a 3-5 m read range, these 900-MHz systems will include RFID tags, readers, antennas, and software.
Recent technological advances have reduced RFID tags to almost semiconductor chip-sized, which is small enough to be inserted into barcodes, other labels, or directly into products. They're usually attached to increasingly smaller cases and packages, and are meant to be disposable, which is referred to as an 'open-loop' application.
Despite these advances, passive RFID tags typically cost 35-45 cents in large quantities, 75-80 cents in small quantities, or up to 85 cents and more for active RFID tags with more reading, writing, data storage, range, and other performance capabilities. Unfortunately, this remains higher than the 5-10-cent threshold that RFID tags reportedly would have to achieve to make them economically viable in most mainstream, disposable, open-loop applications.
Passive tags are powered by the small amount of RF energy that excites them when they enter the electromagnetic field surrounding the RFID system's antenna or reader. For example, 13.56 Mhz tags allow readings at up to 1 m. Once the tag is charged, the reader can interact with it, and pass the tag's data to a linked controller, PLC, PC, or on up to higher-level enterprise systems.
Interference, security, robustness
Similar to any wireless technology, RFID is subject to interference, usually when close to metals and liquids. Physical hurdles typically require more capable and costly tags, readers, or other customized methods.
Simple distance and physical read-write limits usually prevent unauthorized access to tag data, while new RFID Gen 2 standards under development by the EPCglobal organization are expected to address some of these ongoing concerns. Gen 1 is a published EPCglobal standard that is already being used by many RFID developers.
Impinj reports that it recently launched a fully integrated RFID Gen 2 system that includes its fully compliant Gen 2 chips, tags, labels, inlays, and readers.
'Barcodes are the cheapest way to tell what a part is and where it's going, but there are many manufacturing environments, such as paint ovens, chemical processing, and meat packing, where barcodes simply won't work,' says Bradley Todd, Escort Memory Systems' (EMS) marketing manager. 'RFID tags can also aid enterprise resource planning (ERP)-level decision-making during production by handing off data to other tags further along in a process. For example, tags used to track cattle in a trial project in Argentina can add data to the facility's ERP system and write information to other closed-loop tags or barcodes on the packaging.'
Todd adds that Toyota South Africa recently implemented phase two of its RFID vehicle tracking system (VTS), which added EMS' LRP RFID reader-writer antenna and tags to the facility. System integrator EMS SA set up an RFID system that tracks cars through many production stages and final assembly. EMS reports this was an especially significant RFID application because re-useable and disposable tags were used in the same installation.
The first phase installed reusable, high-temperature HMS150 tags, while the second phase implemented LRP-L4982 label tags, which are lower-cost, credit card-sized, disposable paper tags that still have high memory storage characteristics.
'Because RFID tags can be read and written to after each step, any problems can be captured early in the process, which can save a lot of money and time later,' adds Todd.
By itself, RFID appears to have little to do with traditional control and automation. However, aided by databases and other existing information sources, RFID can genuinely aid control and automation, even if it skins that cat indirectly. In fact, upcoming technical advances, such as energy-harvesting, active RFID tags, will likely settle any present arguments by letting the tags serve as wireless transmitters of analog, digital, Ethernet, and/or Internet-based data. 'In the next two or three years RFID tags will likely be combined with temperatures sensors that will be able to continuously write to the tags for constant temperature indications,' says Arnold.
RFID in package connector monitors disinfectant dispensing, quality
Colder Products Co. reports that adding a very small read-write RFID tag to the connector on packaged bags of its liquid disinfectant allows them to be recognized by an 13.56-MHz RFID reader in the coupling that mates with the connectors. This universal dispensing coupling (UDCs) is part of a regulated sanitizing system integrated in AmeriSpa Inc.'s combined footbath/chair systems, which are used to deliver pedicures.
Rick Garber, Colder's smart technology business manager, says once the connector and coupling are permanently seated, information is encrypted on the RFID tag that reports and verifies remaining doses. Once the bag is empty, the tag reverts to real-only status.
Colder's RFID tag consists of a Phillips Semiconductor I-Code 1 RFID chip with 64 bytes, of which 8 bytes are read-only serial numbers, 48 bytes are for general-purpose, read-write data, and 8 bytes control access to parts of the chip.
Besides regulating dosing, Garber explains, the UDCs in the sanitizing system in AmerSpa's footbaths also prevent use of counterfeit cleaners, which potentially could lead to contamination and possible infections. He adds the reader in the coupling may even be linked to with higher-level networking, reporting, and ordering functions in the future.
Basic RFID glossary
Many essential RFID concepts are described by U.K.-based Pelican Control Systems Ltd. on its 'General RFID System Definition' Web page at
RFID tags/labels/transponders are identifiers fixed to items that need to be monitored or processed. Transponders differ in size, memory capacity, physical construction, and range.
Readers/scanners act as the monitoring and/or processing interface between transponders and the data environment. Readers manage the data communications process with transponders and then temporarily store or transmit the information to the data environment.
Operating frequency , typically below 1 MHz, 13.56 MHz and over 800 MHz, determines an RFID system's design characteristics, such as material penetration, data transfer rates, required energy, and operating distances.
Passive RFID systems use transponders energized by an external source, such as the antenna or reader. Passive transponders are usually cheaper than active ones, but their operating distance and data transfer capabilities are limited.
Active RFID systems overcome passive RFID limits by driving their logic circuitry with onboard energy via batteries or wired connections.
Induction, e-field disturbance (also known as backscatter or field disturbance modulation), and radio data communication are the three methods that allow RFID communication coupling between the tag and reader. Induction systems typically operate at low frequency (approximately 125 kHz) with few regulatory requirements, or at 13.56 MHz, where normal radio and spectrum allocation regulations apply. E-field is based on radio energy emitted by the reader, which is collected and reflected by the transponder. Radio data communication occurs when both the reader and transponder communicate using radio signal emissions.
Anti-contention communications protocol. If a system does not use an anti-contention communications protocol, it can only communicate with one transponder at a time. This means that transponders need to be separated and processed sequentially, which in practice may be laborious and time consuming. Anti-contention protocols also differ in their ability to process unique or duplicate identities, different volumes of transponders, and stable or changing populations of transponders.
Read-only memory transponders have a unique code programmed into them by the manufacturer that cannot be changed. The transponder identity has to be associated with a specific item via a lookup table. This provides a high level of data security, but is relatively inflexible.
Write-Once, Read-Many (WORM) transponders can be programmed according to the specifications of the user in a process subsequent to manufacturing. Once encoded, the data cannot be changed. This provides a high level of security, and it is more flexible than read only memory.
Read-Write transponders contain memory that can be modified during normal operation. They're often used in dynamic database applications.