Beyond track-and-trace: Using RFID on the factory floor
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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