Industrial identification success factors

Product identification requires professional planning and industrially suitable infrastructure.

11/08/2012


Industrial product identification (ID) has become a standard task in industrial automation. It is an essential part of a modern production facility. When employed for controlling the manufacturing process, the product identification has to meet the same availability criteria as all other components involved in the manufacturing process. Corresponding components and technologies are available to industry. Designs should account for influences exerted by an industrial production environment, the properties of the product materials, and the application.

The methods for industrial identification are determined by the respective process conditions. For example, a data matrix code lasered into metal is abrasion- and temperature-resistant, and thus can be employed even in harsh environments. Courtesy: SiemenThe need for product identification exists across all industry sectors. There are many industrially manufactured products and a variety of materials to be marked and production conditions to be considered. Successful industrial identification means that the product identification can cope with the requirements arising from the manufacturing conditions, as well as the warehousing and logistics without functional losses, while keeping marking costs to a minimum. Reading reliability of the product identifier under production conditions should be as high as possible, ideally 100%.

Basic technologies

Two basic technologies are available to mark products and/or transport systems for the industrial identification: optically readable markings, such as data matrix code, barcode, plain text recognition, and optical character recognition (OCR); and radio frequency identification (RFID) data storage units (tags or labels). Each technology has its own physically determined strengths and weaknesses.

Optically readable markings

Advantages of optically readable markings:

  • Very low-cost marking methods available (such as inkjet printing)
  • Resistant to high temperatures (laser printing)
  • Resistant to high mechanical stresses (embossing into metal)
  • Reading simultaneously supplies the exact position of the code in the image

Disadvantages:

  • Reading requires positioning in the field of view of the reader
  • Bad visibility in the production affects the reading rate

RFID tags or labels

Advantages of RFID tags or labels:

  • Data media can be written to and are rewritable
  • Low-cost labels available (UHF)
  • Reading makes minimal requirements on the positioning of the product

Disadvantages:

  • Products with high metal content require special data storage types
  • High temperatures require special data storage types or are exclusion criteria

When choosing the basic technology, the product properties of the readers must also be taken into account —besides the criteria for the marking type.

In the case of optical readers, the user can easily comprehend the visibility of the marking in the image as a basic requirement. Professional software on the readers makes special knowledge unnecessary and automatically controls the exposure time, and other attributes. Thanks to a multitude of available lights and lenses, the use in a wide range of industries is assured.

RFID readers and writers are available for a wide range of reading distances. Compared to optical readers, an exact positioning of the objects to be acquired is not necessary. In contrast, the precise characteristics of the detection area (field strength, reflections) can only be defined with considerable technical effort.

Applicable to both technologies is that the industrial suitability with regard to IP protection rating and interface method (industrial networks such as Profibus, Profinet, and others) must be satisfied by the devices.

Only when using the right basic technology and high-performance readers can product identification with maximum reliability under the harsh production conditions be achieved. Some code readers for optically readable codes or optical character recognition (OCR), or the RFID readers/writers offer the necessary performance. They can ensure the trouble-free operation of the identification process—even during fluctuating process conditions, such as concerning marking quality, lighting conditions, or product position.

Industrial identification

Industrial identification refers to the identification irrespective of the basic technology used. In practice, the technology is often changed when transitioning between the production and logistics. The reasons for this are the different conditions of the two process steps. During production, the individual product is typically transported unpacked and is therefore visible; while in logistics, the packaged product—also in larger quantities—needs to be captured as a unit. For logistics, the possible bulk detection by means of RFID is thus of particular interest. In the production, however, the low-priced identification with optical readers can be employed.

RFID and code readers can be operated interchangeably at the communication modules. Courtesy: Siemens Industry

Switching between the two basic technologies is supported by the RFID and code reading systems through a pin- and protocol-compatible interface. Switching between optically readable codes and RFID tags can therefore be easily realized by swapping systems. For the user, committing to a physical product identification principle—and its strengths and weaknesses—thus becomes considerably less challenging. With some systems, the switch can be made without modifying PLC programming by using standard function blocks. It is even possible to switch between RFID and optical codes as marking technology during the manufacturing process, thus taking advantage of the respective strengths, such as when handling heated-up products. Here, an RFID tag and optical code could be given the same contents. But even the above-described transition from production to logistics is greatly facilitated.

Successful system integration

To successfully run industrial identification, the industrial suitability of the automation technology is important as well. Demanded here are industrially suitable communication and engineering suitable for large plants.

Industrially suitable communication is needed because only the combination of successful reading of the product identifier and error-free transmission of the reading result enables a trouble-free operation in the respective application. Devices communicate via various industrial networks. Based on these fieldbus standards, transmission accuracy is assured. The decision for these protocols provides the user with corresponding industrial-grade components (with regard to connector technology, cable material, etc.) and other devices (such as switches). Furthermore, these standard protocols offer comprehensive diagnostics functions, which optimally support troubleshooting and error correction, minimizing commissioning times and plant downtimes.

Especially for optical code readers, the application-specific triggering of the reader represents a critical point of the integration—next to the transmission of the reading result. The triggering usually occurs by means of a separate sensor, such as a light barrier, whose signal is forwarded to the reader. Some readers can automatically detect the presence of a code in the image area. That function is particularly useful for applications, where a reliable triggering is difficult or extremely expensive due to missing varying product characteristics. In these situations, this functionality helps ensure the operational reliability of the identification at a low cost.

Communication modules enable the use of many connector technologies and bus systems; depending on the requirements, a suitable identification system can thus be employed. Courtesy: Siemens Industry

An important part of the system integration is the integration of the readers into the visualization concept of the plant. Code readers can support integration of visualization into already existing human-machine interface (HMI) devices. As a result, separate visualization hardware is not needed for the identification technology, reducing construction costs, the space requirement, and the wiring of a plant. During trouble-free operation, the visualization for identification devices typically entails the output of the reading result. In the case of a faulty reading, however, the underlying image is of special interest to the machine operator, especially with optical code readers. Siemens optical readers make using the integrated user interface—either as stand-alone application or as integrated component of a plant user interface—extremely easy with an integrated Web server. The user can use the Web-based user interface without having to do his or her own testing or having to integrate the reader through custom programming.

Standard functionality

Siemens offers identification technologies. Courtesy: Siemens IndustryIndustrial identification has become a standard functionality in industrial manufacturing. The two basic technologies, RFID and optical codes, offer product identification for virtually all applications. With high-performance systems (RFID and optical readers), the customer can freely choose between the basic technologies and their corresponding device infrastructure. The devices provide industrially suitable operational reliability with regard to identification and plant integration. As a result, the door to a successful industrial identification is wide open.

- Michael LaGrega, MCSD, RFID+, is RFID and code reading systems engineer, Siemens Industry. Edited by Mark T. Hoske, content manager CFE Media, Control Engineering, mhoske(at)cfemedia.com.

Key considerations

  • Industrial identification depends on the production environment, product properties, and the application.
  • 2 ID options are optically readable markings and RFID
  • Consider reader properties when looking at basic technologies

Consider this

What information should travel with assets in your plant via RFID to enhance productivity? 

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