Beyond track-and-trace: Using RFID on the factory floor
RFID has moved beyond logistics to become a link between the plant floor and the enterprise.
Industrial manufacturing continues to evolve, constantly adapting to meet the ever-increasing productivity and efficiency demands on the factory floor. RFID technology has been providing manufacturers with high-quality, reliable product track-and-trace functionality throughout the supply chain, but this intelligent monitoring system technology is also a valuable asset within the production environment. By using RFID as a manufacturing tool, companies are redefining production standards with improved execution, efficiency, and product quality.
Before RFID systems that could withstand extreme environmental conditions were developed, manufacturers were not able to achieve the unique visibility and control this technology offers. Now that RFID can perform in high temperatures, high pressures, hazardous locations, and wet environments, manufacturers can use these systems for automated processes to control and monitor operations and refine schedules, directly impacting their efficiency gains and improving production (see Figure 1).
RFID offers major advantages compared to optical identification methods such as barcodes. The use of this technology spans a diverse range of industries including oil and gas, chemical, pharmaceutical, automotive, and other industrial manufacturing processes. By incorporating RFID tags and readers into the manufacturing environment, users can increase production visibility and control with continual real-time status updates. Providing immediate access to tool locations, equipment tracking, and process data, RFID delivers an essential element for achieving previously unmatched production streamlining.
How it works
When selecting and implementing the appropriate RFID solution for each application, manufacturers should know the speed and proximity required for products to successfully pass the read/write heads. Variables such as data size and distance also impact the viability of the solution. Therefore, supplying only general information such as recommended read/write intervals or transfer rate is typically insufficient when identifying the appropriate system for the application.
Unlike conventional auto identification methods, such as barcodes or the data matrix code, RFID transmits information using electromagnetic radio waves, which eliminates line-of-sight requirements. While printed labels attached externally to a product or component become unusable by the time they are exposed to high temperatures or moisture, special RFID tags and mobile reading devices make it possible to use RFID systems even under harsh industrial conditions.
An RFID system contains three parts: tag, transceiver, and interface. Tags can be active (requiring a battery) or passive, reflecting the signal back to the transceiver, which is often called a reader or antenna. The interface transfers the data from the tag to a data collection device such as a computer or a PLC.
The transceiver reads the RFID tag. An I/O device communicates with the enterprise or higher-level control system to provide tag information. RFID tags contain internal circuits that respond to an RF field emitted by the transceiver. During operation, when an RFID tag passes through the transceiver’s field, the tag detects the signal from the antenna. This signal activates the RFID tag, enabling it to transmit or receive information on its microchip.
Originally, this technology was developed as a method to remotely gather data through tags or transceivers. However, because of their data storage capacity, manufacturers have been attaching or embedding these tags into objects during production and programming them with information about the product, equipment, or tool. By gathering more data through tags, RFID allows users to read and write meaningful data—process information—to the tag.
Some RFID systems feature state-of-the-art nonvolatile ferroelectric random access memory (FRAM) storage technology, which allows 106 write operations and an unlimited number of read operations on a single data carrier. With this type of read/write capacity and the ability to be used in applications that require repeated write operations, manufacturers can reduce or eliminate replacement data carriers. Plus, RFID systems now exist that allow read and write operations to be easily programmed to the data carriers at any location with a handheld unit and enable data to be displayed on an illuminated touchscreen in decimal, binary, hexadecimal, and ASCII code formats. From this point, manufacturers can easily and conveniently manipulate data, editing and writing it to the appropriate data carrier as required.
To accommodate versatile and challenging application requirements, data carriers are available in a variety of shapes and feature diverse read/write intervals, with high-frequency technology allowing read/write operations at distances from 5 to 500 mm, and UHF technology allowing read/write operations at up to several meters.
Systems have also been designed to withstand a wide temperature range, including data carriers that can operate in extremely high temperatures and those that require no cool-down time for read or write operations. These enhanced thermal characteristics can significantly increase productivity rates on the plant floor. Additionally, to satisfy fast-paced manufacturing environments, innovative RFID systems have been engineered to read or write data simultaneously at 0.5 msec per byte, and some are even capable of on-the-fly production speeds of 10 msec at distances up to 500 mm.
Along with meeting speed and distance requirements, RFID must also be adaptable enough to adapt to industry changes. For inherent scalability, modular RFID systems with built-in I/O capabilities enable this technology to keep pace with growing manufacturing demands. Users can add discrete, analog, and/or eight-channel RFID modules to the system to expand single network nodes. RFID can be integrated into existing platforms and supports common protocols including Profibus-DP, DeviceNet, Modbus TCP, Profinet, and EtherNet/IP, which allows flexible connectivity, communication, and production visibility.
RFID on the plant floor
While tracking products through the supply chain can promote product quality and customer satisfaction, RFID can also be used internally to improve process efficiency and decrease costs. For example, manufacturers can use RFID technology to monitor equipment within the facility by tagging machines, conveyors, trucks, or forklifts. Through these tags, users can access data on the contents, location, usability, and maintenance requirements of each piece of equipment. This knowledge enables users to decipher production status information, identify potential problem areas, and help develop planning strategies for production performance optimization and effective labor/asset allocation (see Figure 2).
Accurate inventory information is important to the efficiency of every plant. RFID technology can help improve inventory management. By tracking products and equipment, RFID helps regulate the inventory of a manufacturing unit, allowing users to better forecast their needs with real-time data on raw material, equipment, or supply demands. Also, by maintaining equipment and tool location inventories, RFID can improve production scheduling or eliminate the need to reorder materials that are thought to be lost.
When RFID is implemented for inventory management, users can effectively reduce costs and waste by applying the technology to increase product visibility and enhance stocking/reordering processes. RFID can locate tagged materials and supplies. Using RFID technology to manage equipment and tool locations allows users to improve production scheduling by identifying which objects are in use or can be allocated to a specific project. Further, the ability to pinpoint the amount of remaining supplies and their exact locations can improve production line movement, decreasing downtime and shrinkage.
Because plant floors are often busy, chaotic environments, shrinkage is common. Inventory shrinkage refers to a number of unrelated causes that render products unaccounted for under inventories. This could include materials that are no longer usable or items that are lost or damaged. Shrinkage can also occur when employees purposely keep assets/tools accessible in convenient places. This makes it appear as though these items are missing from inventory, leading to unnecessary replacement purchases. With RFID tracking in place, locating these assets is easier, which saves search time and replacement costs.
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Maintaining accurate records about the progress of a particular manufacturing process is tedious, often requiring time-consuming manual data entry. This procedure also increases the likelihood of errors and incomplete information. Without up-to-date data, productivity can suffer. Therefore, using RFID to track manufacturing work-in-progress improves workflow productivity and efficiency.
RFID can be used to tag work-in-progress applications, which enable real-time part or product location tracking and allow assembly line status updates. With tags at specific production stations, users can get continual updates on the progress of a particular item or process. This ensures that the right materials reach the right places at the right intervals and prevents costly downtime to correct mistakes (see Figure 3).
Using RFID for work-in-progress enables plants to coordinate the use of equipment, manpower, and material resources. RFID is well suited for manufacturers who build several products on a single production line, or who manufacture complex or customized products in multiple plants in multiple locations. Production planners and inventory control personnel use RFID tags to automatically update customer data and finished goods inventory.
By integrating RFID as an internal manufacturing tool, users can improve how information is transferred within the enterprise, while reducing costly mistakes and excess labor expenses. Using an RFID reader and PC that automatically captures and communicates data—rather than creating data entry sheets manually—eliminates potential errors in the system. RFID tags can be applied to subassemblies to enable automated, unattended work-in-progress tracking, and can be interfaced with industrial control systems to automatically route items through assembly processes. This avoids relying on manual data input, which increases process speed and accuracy.
RFID in action
RFID has become a valuable device for improving production performance and lowering costs in a wide variety of industries, and it has been replacing traditional optical identification technologies to overcome durability challenges and downtime associated with those options.
For example, to track and monitor every intermediate or final product, conventional optical identification methods, such as barcodes or data-matrix codes, use externally attached printed labels. This makes them vulnerable to destruction from environmental conditions such as high temperatures, moisture, dirt, or abrasion, which could render them inoperable. Also, barcodes and data-matrix codes cannot provide more than basic item information, they cannot be written to, and automated identification and production-control data do not become fully integrated into the system. However, RFID technology effectively overcomes these challenges because of its durable housing and its capability of transmitting more information.
The steel production industry is an example where RFID technology adds significant value to the process (see Figure 4). Large cranes transport from 90 to 425 tons of raw materials used for steel production in huge ladles throughout the plant. If something goes wrong, the best-case scenario is a significant amount of lost time. But the worst-case scenario could be severe damage caused by molten metal or bulky ladles.
By implementing an RFID system and special sensors that feature an expanded temperature range of up to 212 F, ladle transportation within the plant can be precisely tracked. This prevents costly and time-consuming errors from occurring during transportation. An RFID read-write head mounted near a crane rotor disk records the signals of transponders mounted at specific points on the rails, which allows precise location and coordination with the main control unit’s travel sensors. Using the known tag positions, a PLC can calibrate the rotary position transducer signal. This prevents position errors and enables safe and efficient transportation.
RFID technology also provides progress tracking for assembly line procedures. For example, in semiconductor manufacturing plants, RFID can be used to check for correct wiring before the chip modules are transferred to the good-parts magazine. RFID technology is used along the production line to document process steps directly on the parts carrier. The first read-write tag can be located on the loading-machine outlet where the data carrier receives information about whether the designated components were successfully mounted and if the assembly can be further processed. If the necessary components are accounted for, the data carrier content is updated so it includes the processing release.
This process continues at each processing station, where information regarding the success of each step is added to the data carrier as the product moves through each station. Finally, at the last RFID station, the data are exported and the operator forwards the individual parts to the good-parts magazine or the reject parts punch, depending on their status on the data carrier. For record accuracy and comprehension, this production data is then archived according to each batch in a report file.
RFID technology can also assist in meeting production deadlines or delivery schedules. A plant that provides flexible delivery programs such as just-in-time delivery of parts or assemblies to other manufacturers has very little warehouse or storage capacity. This means that equipment must operate efficiently and in perfect harmony to meet orders. To ensure production runs smoothly, these facilities rely heavily on automation. Therefore, using an RFID system that can communicate with traditional fieldbuses without a PLC—and that features its own data memory and adapts automatically to the application—can help maintain required production speeds.
To meet the needs of constantly changing production demands, modular RFID modules can be adjusted so that each channel works with a read/write head separately in parallel/multiplex mode. This is particularly important for applications where two read/write heads are located very closely to one another, such as when a conveyor chain splits into several chains. Further, RFID with FRAM memory and high-speed read/write capabilities enables faster data transmission and requires very little maintenance. This allows manufacturers to reduce the read/write time per station. Because stops for reading and writing are no longer necessary, the system can accommodate a faster conveyor speed, resulting in higher throughput.
The future of RFID
Market competition demands that manufacturers continually seek new ways to improve production. RFID technology offers an intelligent, low-maintenance solution that delivers significant benefits. Implementing RFID technology on the plant floor enables users to improve accuracy, provide faster production speeds, minimize errors, and significantly reduce material and labor costs.
Randy Durick is director of the Network & Interface Division of Turck USA and has held this position for four years. He has worked at Turck for more than 10 years and has more than 15 years of experience in sales, business development, and product management in both the process and industrial automation industries.
This article appeared in the February 2013 Applied Automation supplement to Control Engineering and Plant Engineering, both part of CFE Media.
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