What makes RFID systems industrial strength?

Balluff Pty Ltd

Wednesday, 31 August, 2016



What makes RFID systems industrial strength?

The retail environments where products are sold look nothing like the industrial environments where they are produced, yet the same RFID products developed for retail stores and supply chain operations are heavily marketed to manufacturers for production operations.

Many of the RFID products marketed to manufacturers may have different housings or IP ratings than their general-purpose cousins and may work fine in warehouses, but that does not necessarily qualify them as industrial grade.

Production environments often have their own ruggedness, performance and connectivity requirements that only purpose-built industrial equipment can reliably satisfy. For example, general-purpose RFID equipment may have the physical Ethernet port needed to connect to a PLC, but will not support EtherNet/IP, Profibus or other industrial protocols that are used to network with PLCs and other industrial automation equipment. The reader will need to be supported with additional protocol conversion, which slows system performance and adds to implementation time and expense.

EtherNet/IP and other industrial protocol support is just one example of the many features that separate true industrial RFID solutions from products that can be used in industrial environments. When evaluating RFID equipment, it is important to make the distinction between what is possible for use in the environment and what is optimal.

Three fundamental qualities determine if RFID systems will perform reliably in demanding production environments:

  • Will the RFID system integrate seamlessly with industrial control systems?
  • Will it provide the reliability and speed that production and information systems require?
  • Can it maintain uptime and performance long term — will it last as long as the production line?

Will it integrate seamlessly?

RFID is often marketed as a ‘solution’ but in manufacturing operations it is almost always used as a supporting technology to provide data and visibility to the MES, ERP, e-Kanban, robotics, asset tracking, material handling, quality control and other systems that run production facilities. The first requirement for any industrial RFID system is to be able to seamlessly integrate with the enterprise’s production control systems — including PLCs, sensor networks and HMIs — and the industrial protocols that run them. Failure to accurately provide data to these systems, at the reliability and speed levels they require, eliminates the value of using RFID.

The need to support control systems produces a fundamental disconnect between supply chain-oriented RFID products and industrial user requirements. Most RFID readers are programmed to process ASCII data, yet PLCs and other industrial automation equipment run on industrial protocols like EtherNet/IP, Profibus, Profinet, CC-Link, DeviceNet, EtherCat, etc. Industrial protocols are binary and thus can transfer data much more quickly than ASCII-based systems, because ASCII characters consist of more bits. Converting data streams from ASCII introduces an extra step that adds time and therefore limits productivity. The delay caused by protocol conversion is often unacceptable in automated production environments where, for example, a work-in-process item may need to be identified, recorded and routed to the next process, all in three seconds or less.

There are RFID readers with native support for industrial automation protocols, but it is not a common feature. Some vendors do not even offer industrial protocol support as an option, which is a key indicator that the products and vendor are not focused on the industrial market.

Protocol conversion is typically done by developing software code to convert the RFID data string to the specific protocol, and installing it on the RFID reader or industrial automation equipment. The software development time is often a hidden cost that is not considered during system planning and hardware evaluation. Developing, testing and installing the code increases the time needed for system implementation. These cost and time factors illustrate why it is difficult to make apples-to-apples cost comparisons between industrial and general-purpose RFID readers.

This reduction in performance for RFID readers that do not have native support for industrial protocols would not be reflected in the product spec sheet, which may list how quickly tags are identified, not how quickly the data can be processed and presented to the host system. RFID readers without direct support for native protocols introduce risk, cost and performance limitations without providing any additional benefits.

Will it be reliable at production speeds?

The physical environments in industrial and supply chain settings cause RFID technology to perform differently. The primary source of potential interference in retail and supply chain environments derives from having hundreds or thousands of tags in close proximity. Tag density is also a consideration for industrial RFID users, but their environment has much more challenging and powerful potential interference sources. These include electromechanical equipment, sensors, wireless controls and other automation equipment, whose signals can impede RFID performance. Metal is a leading source of interference for ultrahigh frequency (UHF) RFID technology for example, so many production facilities are very challenging environments because of the many metal products, equipment and tooling that are present.

RFID systems for industrial environments should have built-in protections against these potential interference sources. As noted earlier, it is essential for RFID systems that support industrial automation systems to be extremely accurate and reliable. An RFID misread at a library checkout counter or retail store is an inconvenience; in a factory it could cause production line delays that cost thousands of dollars in lost productivity.

RFID systems are most reliable when tags and readers are matched to the environment. While the retail and supply chain industries have standardised on EPCglobal Gen 2 and ISO 18000-6 standard UHF technology, industrial systems often require a range of RFID technologies including UHF, high frequency (13.56 MHz), low frequency (125 KHz), microwave (2.45 GHz) and real-time locating systems (RTLS), which are available in multiple frequencies. High frequency (HF) tags are especially effective for production operations because they are resistant to interference from metal and have the memory capacity to carry production data other than a serial number. However, HF has limited read range, typically less than 60 cm, so the technology may be appropriate for tracking carriers that convey items through controlled locations in production processes. UHF is favoured when readers or personnel can’t be positioned near production or for intralogistics purposes. UHF technology can be used to provide much more range from approximately 1 m to 6 m, but is limited in memory (typically 512 bits).

One of the best ways to minimise interference and maximise reliability is to use RFID tags that are optimised for the objects they are identifying and the environments where they are read. Multiple tag types may be required, including specialty tags designed to be read when applied on or near metal. Tag designs can overcome some environmental challenges, but different RFID frequencies may also be required to get the required performance in different process areas.

For example, some manufacturers use HF tags on the conveyors that route assemblies through the production process. The tag is encoded with the assembly serial number and is updated with variable production information such as build data, error-proofing results and configuration information during the manufacturing process. When production is completed and the part is ready to be shipped to the next stage of production, the part ID or other data from the HF tag can be automatically collected and used to encode a UHF tag on the RTI (returnable transport item) or other container used for logistics, without any manual data entry or operator intervention required. The UHF tag could also be used for internal material handling, storage and shipping processes.

Since a range of RFID technologies is typically required for industrial operations, selecting a vendor capable of supporting multiple options like LF, HF and UHF is critical. Some industrial RFID readers even have the ability to simultaneously support input from different frequencies (eg, HF and LF) and integrate with I/O modules that support sensors, PLCs and other industrial automation components.

Will it last as long as the production line?

Companies are accustomed to having their PLCs and other industrial automation systems last for many years, and have similar expectations for RFID equipment. Reliable performance and a long product lifespan are attainable in production environments, but will require purpose-built equipment. There are a few tell-tale features that differentiate rugged RFID products. These include objective ratings and certifications, base materials and fundamental product design.

Products that are marketed as ‘rugged’ or offer an optional protective casing are not necessarily appropriate for an industrial environment. IP, IEC and EN ratings and other independent certifications provide some insight into ruggedness and suitability, but they are just a starting point, and not a guarantee that the equipment will function reliably. RFID products designed for use in a distribution centre will not be exposed to the same levels of shock, vibration, humidity, temperature, radiation and interference as units that are used in production processes, which may include assembly, painting, stamping, grinding, welding, chemical treatment, cleaning, sterilisation, freezing, heat treatment, vibration testing and exposure to hazardous materials. For reference, many UHF RFID readers developed for warehouse and supply chain operations have an IP54 rating, whereas IP65 and EN60068 rated RFID systems are preferable for many production environments.

While IP ratings do not guarantee performance, IP65-rated RFID systems do have advantages over IP54 models in real-world production environments. IP65 devices, and individual parts that are EN 60068 rated, provide superior protection because they can withstand more shock and vibration. They are sealed against liquids, dust, dirt and other substances that could potentially penetrate a device and cause it to fail.

Smaller, subtler differences between products often have a larger impact on reliability and performance. For example, cable connections are a common point of failure for all types of electronic equipment. RJ45 and other connectors that snap in or clip in are particularly vulnerable. They can easily become broken or unplugged if the cable is tripped over or otherwise disturbed. Industrial products should be protected against this potential point of failure with threaded connectors that screw in (such as M12 type) and will not detach or break because of vibration or incidental contact.

Fundamental industrial product design calls for all components to be housed internally so that exposure to hazards is minimised. Unfortunately, RFID antennas often must remain external for maximum performance, and thus represent a vulnerability. Damage risk can be reduced by constructing antennas from durable materials, including secure connectors and by offering multiple mounting options. RFID antennas are available with IP65 ratings and certifications to withstand various levels of shock and vibration.

When determining whether RFID products are suitable for a specific environment, it is important to look beyond published marketing hype and misleading specifications. Consider the design and construction of the product and how it could be affected by various work processes. Whenever possible, products should be tested where they will be used rather than in a lab or demonstration area, because the actual work location has interference and environmental conditions that may be overlooked and impossible to duplicate elsewhere. It is very important, for example, to have a professional RFID site survey conducted when using UHF before systems are installed. During a site survey professional RFID technicians or engineers will identify potential sources of interference, evaluate location options for installing equipment, measure signal strength and collect other information so the UHF RFID system can be tuned and optimised for the specific facility. The skill of the person who conducts the site survey — as well as the overall skill, experience and breadth of product options of the RFID system provider — can greatly improve system performance and reliability.

Summary

It takes more than product packaging, ambiguous specification and clever marketing to make RFID products truly industrial. To meet the operational and business requirements of production facilities, RFID equipment needs to seamlessly integrate with industrial automation systems and work reliably in challenging conditions — and to do so for years without causing unplanned downtime. The key attributes that differentiate industrial RFID equipment from supply chain-oriented alternatives include:

  • native support for industrial protocols;
  • high tag read reliability and the ability to continuously operate at speeds that won’t slow production systems;
  • durable housing with secure connectors;
  • IP65 rating and relevant certifications for shock, vibration and temperature resistance;
  • the ability to support multiple RFID technologies and supporting devices as needed, including sensors, PLCs and other industrial automation equipment.

Compromising on any of these criteria will likely result in unnecessary implementation, support and replacement costs and raise the risk of system failure. These risks are greatly minimised when appropriate equipment is used, as industrial RFID systems have proven their reliability and value in a wide range of challenging environments.

Image: ©stock.adobe.com/Hamik

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