RFID printers/encoders became symbols of the quick integration of RFID technology into existing business processes, mainly as a response to mandates from major retailers or the U.S. Department of Defense (DoD). Buying just a printer allowed people to quickly create RFID labels with an electronic product code (EPC) number encoded on them. This process has been called slap-and-ship: an RFID printer prints and encodes shipping labels with RFID tags that are then placed on products before being shipped to a mandating customer such as Wal-Mart, Target, or the DoD. In this case, RFID is not fully integrated into the company's business process and it is not used for internal benefit. This is one of the reasons people complain of RFID having no value; in this slap-and-ship instance, it is purely a cost.
However, more and more companies are using RFID as a strategic competitive advantage, and have done a detailed analysis to find value drivers by using RFID. What that means is that they are investing in full RFID integration, with RFID printers being used at various points of the business process for printing, encoding, and validation of RFID labels. Printers are often either used in conjunction with automatic label applicators or applied manually during exception processing.
Most RFID printers/encoders evolved from a barcode printer. Companies such as Zebra Technologies, Printronix, Intermec, and Paxar evolved their barcode printers by integrating an RFID reader board onto them. RFID printers/encoders have gone through several iterations and improvements during their development life cycle, from the early days when I saw printers that literally had an RFID reader bolted to the back of them.
The current version of RFID printers not only prints information on the label, but also encodes and validates the RFID tag in the label via wireless data-transfer protocols. If the tag's function is not positively verified, the printer prints the word "void" or a large "X" on the label to inform the operator that this tag does not work, and automatically issues a new replacement label. The main reasons for a rejected label to be marked "void" are the following:
The label medium does not carry an RFID tag, or the tag works on a different frequency than the printer. (For example, a high-frequency tag would not be recognized by an ultra-high-frequency printer.)
The label medium contains tags that, although they operate within the correct frequency, size, and location, operate under different air interface protocols.
The printer was not calibrated for the location of the tag's antenna on the label. The printer manufacturers publish label and tag specifications, and you should have your RFID labels made according to these guidelines. If your labels do not comply with the printer's default specifications, the printer has to be properly calibrated.
The tag was damaged after the manufacturing and verification process or faulty from production. Damage could have been physical or by electrostatic discharge (ESD). ESD is discussed further later in this chapter.
Although each printer is different and each manufacturer will supply a manual that will guide you through a printer installation, let's look at some common techniques and best practices that you may find useful in your future printer deployments. There are several things that need to be taken into consideration when installing and working with an RFID printer; one of them is the issue of ESD, which I will discuss once we go through the printer installation guidelines.
When you are installing an RFID printer/encoder, you should adhere to the following guidelines:
Unlike putting together toys for your kids at Christmas, when working on RFID equipment you should always read the printer manual supplied by the manufacturer (this is important for any device you work with). This will allow you to avoid mistakes when installing this device and ensure its proper function, and you are less likely to have leftover screws and bolts.
Place the printer on a solid, level surface and ensure proper ventilation. Heat and humidity can be one of the big killers of RFID equipment.
Make sure that you will have enough space to open the printer and change the print supplies, as well as access to all buttons, ports, and cables. Sometimes it is a good idea to place the printer on a cart to improve its accessibility and mobility.
Find out what ports you have and need to connect to other devices or networks. Printers usually come with standard communication interfaces such as RS-232 serial data port, bidirectional parallel port, USB 2.0, RS-422, and sometimes RS-485 port. For an Ethernet-based network connection, you may have to use a print server that has an Ethernet port. Several printer manufacturers also provide additional communication capabilities through Bluetooth or 802.11 wireless networks. (Bluetooth and 802.11 wireless capabilities usually require appropriate print servers, but these options can be integrated into some printers.)
Make sure that you have an accessible, grounded power outlet for the printer to plug into.
A power cord may or may not be included with the printer. If your printer does not come with a power cord, consult the manufacturer's manual for guidelines regarding selection of a proper type and length for the power cord. You will usually need a three-conductor HAR (harmonized) cable with an IEC 320 connector certified by an international safety organization. This is what most desktop computers use these days, so you are likely to have one somewhere.
Select the correct media (printer ribbon and labels) for your printer. This depends on the printing method you will use as well as other label and tag requirements.
When installing a printer, you should take electrostatic discharge (ESD) into consideration and protect your device as well as personnel against its effects. ESD refers to the rapid release of charge that has accumulated on a person or object. Most materials can be electrically charged by friction; the amount of charge is highly dependent on the material, speed of contact and separation, and environmental humidity. Electrostatic discharge can cause damage to any unprotected device, and this damage can induce either immediate or later failure of the device or its components. ESD can also harm your team, so be careful!
According to the Electrostatic Discharge Organization, walking across vinyl tile can create a static charge of 250 volts at 65 percent to 90 percent humidity. The same action will generate 12,000 volts at 10 percent to 25 percent humidity! Electronic components can be damaged or destroyed by discharges lower than 100 volts, in some cases even by discharges lower than 10 volts!
ESD can cause problems in RFID printers, where the movement of unwinding media and the printing ribbon through the printer generates an electrostatic charge. The discharge could damage the printer as well as the tag's chip and cause malfunctions. This has been solved by implementing special ESD bristles inside the printer and by proper grounding. If you use a proper power cable for your printer (the cable should have a ground line and a total of three prongs), and the power outlet or power strip you connect to is properly grounded and complies with all electrical building grounding regulations, you do not usually need a second ground. As a matter of fact, in this situation, a second ground could lead to a ground loop that could damage the device.
ESD also can be generated by peeling the label off its backing. This charge can be temporarily stored on the label or it can be discharged onto the product that the label is applied to. The released charge can then cause damage to this product or to the RFID tag within the label. Some label manufacturers produce labels that dissipate static and reduce the possible product and component damages.
Generally, you must always use proper grounding, and possibly humidifiers in severely dry environments, as a means of ESD protection for your personnel. You may also need other devices such as static mats or special shoes or bracelets.
Today, many types of tags have a near-field loop as a part of their antenna design. This helps create a balance in static electricity for both sides of the tag and reduces the possibility of ESD and its damaging effects on the tag.
There are two major printing methods used with RFID printers. They are direct thermal and thermal transfer .
The direct thermal printing method requires heat-sensitive RFID media and no printing ribbon. Information is printed as the printhead applies heat directly onto a heat-sensitive label.
The advantages of the direct thermal printing method include the following:
No need for a ribbon. Sometimes the manufacturer recommends using a ribbon with the direct thermal method to protect the printhead; however, this is not a rule and it may cause errors in some printers.
The disadvantages of the direct thermal printing method include the following:
Heat-sensitive media are more expensive.
Print is less durable, especially when the printed labels are subjected to heat. In high temperatures, the print on the label will fade away (similar to a receipt from a gas pump left in a car during the summer).
Direct thermal printing is often used by mobile printers because this method has proven superior and more cost-effective for immediate "in the field" application of RFID/barcode labeling.
The thermal transfer printing method requires RFID media (labels) and a printing ribbon. The ribbon is a wax- and/or resin-coated plastic strip that is available in rolls. The coating is transferred by a printhead onto a label, creating the printed information.
The advantages of the thermal transfer printing method are as follows:
Print is more durable (especially when using a ribbon with a resin coating).
Labels are not as heat sensitive as the labels used for direct thermal print.
Thermal transfer printing withstands high temperatures.
The disadvantage of the thermal transfer printing method includes the following:
It requires the added cost of using a printing ribbon.
There are several kinds of RFID labels. They differ by type (whether they are used for thermal transfer or direct thermal), size, and form.
As mentioned in the previous section, direct thermal labels are heat sensitive, whereas thermal transfer labels are not, but they are coated to hold the print wax and/or resin transferred from the ribbon.
If you need to find out whether the label is intended for direct thermal or thermal transfer, scratch the surface of the label with your fingernail. If a black mark appears on the label, it is intended for direct thermal printing.
Labels come in various sizes; the most common are 2˝ × 4˝ and 4˝ × 6˝, but sometimes you can find 4˝ × 4˝ or 1˝ × 4˝ and other sizes. You should select the size of a label according to your requirements for the amount of information being printed on the label, the size of your product, and your choice of a tag and its antenna size and pattern. Generally, you will be able to use small labels with single dipole tags, while the dual dipole tags will require labels with a larger surface. Most companies I've worked with have an existing label requirement from their customers-there is usually some bar code (machine readable) and text (human readable) information on a standard-size label. The label manufacturers have been smart enough to understand this and make these same labels with an embedded RFID tag.
Most of the labels are supplied in the form of rolls (labels stick onto a backing and are rolled onto a core); sometimes they can be fan-fold (labels stick onto a backing and are folded zigzag into a fan). Rolls are usually placed inside the printer; however, fan-fold media can be fed to the printer through an opening in the back of the printer's body while staying in its original packaging.
If you intend to use your labels in extreme environments, mainly in extreme temperatures, make sure that you purchase labels that will withstand them. For instance, in low temperatures, the regular adhesives used on labels will not stick and you would have to find another method to ensure that the labels stay on the product. Similar problems can come up in high temperatures, when the adhesive can "melt" and stay on the label backing when you peel the label off.
Media can also be continuous (contiguous), where the labels are on an uninterrupted strip (roll) of material, or noncontinuous (noncontiguous), where a hole or a notch separates the labels.
Sometimes it can be difficult to thread the printer with the media and ribbon; therefore, in some cases, the manufacturer provides arrows on the inside of the printer's case that you can follow in order to thread the labels or ribbon correctly.
To work properly, the installed printer has to be configured. This usually can be accomplished either directly on the printer through its front panel or through printer programming language, or remotely through middleware.
Manufacturers usually provide an option to configure their printer for printing labels and encoding RFID tags through a printer-specific programming language. For example, Zebra provides Zebra Programming Language (ZPL) and Printronix developed Printronix Programming Language (PPL). These programming languages are based on commands that are written in a text editor in a specific sequence and sent to a printer through a communication interface.
To fully set up an RFID printer, you must configure printing settings, RFID settings, and network settings. When configuring printing settings, you have to choose an appropriate print mode, media type, contrast of print and input label length, and other label positioning information.
When configuring printing and label properties, you can usually choose from default settings if you are using labels manufactured or intended for that type of printer. However, sometimes you will need to change the settings according to your application and conditions. Because the settings differ by the printer and its manufacturer, the safest way to make changes is to refer to the printer's manual.
RFID settings consist of information about the RFID tag. You have to supply the type of RFID tag (whether it is an EPC Class 0, Class 1, Class 1 Generation 2, or ISO 18000 tag part 6A or 6B) and its EPC length (64 or 96 bit) or memory length. The next setting is the inlay positioning on the label, which is important mainly if your label converter did not follow the specifications for the inlay placement given by the printer manufacturer. Another important setting is the read and write power of the printer. The recommended power is specified by the tag manufacturer. If the power is set too high, especially with small labels and inlays placed close to each other, you could read or write to neighboring tags by accident.
Communication settings include IP address, subnet mask, and default gateway. This information is important in order to communicate with your device through a network.
After the printer is configured, it is a good idea to print a configuration label. This can be done in many ways, which differ by manufacturer. The configuration label carries all the information about the printer and is useful as a record of the printer's settings for later troubleshooting. Configuration labels include not only information about the print mode, media, and sensor settings, but also network settings.
To make your job easier, most printers are able to configure themselves by calibration. There are many ways to calibrate an RFID printer, which differ by the type of printer and its manufacturer. Each type of calibration varies by the amount of time it takes to calibrate the printer, the number of labels used (they can usually be put back and used again), and its reliability. Many printers have an auto-calibration button ("Calibrate" button) on the front panel, which triggers the process of calibration when pressed. You must make sure that you calibrate the printer every time you use a new type of label and RFID inlays, especially if they are not specifically made for your type of printer.
To write to tags with your RFID printer/encoder, you must make sure that your tags have encoding capability. You'll also need to know the tag's memory size. As discussed earlier in Chapter 4, "Tags," RFID tags are divided into classes. EPC Class 0 specifies that the tag is read-only; therefore, it cannot be written to. EPC Class 0+, Class 1, Class 1 Generation 2, and ISO 18000 are writable, and therefore you will be able to use an RFID printer/encoder to modify the tag's memory and encode it with information. By the end of 2006, Gen 1 tags will be obsolete and there will be no need to consider this option. What will become important are the frequency and the standard. Both Gen 2 EPC and ISO 18000 will have UHF and HF standards.
You can use the printer programming language to create your label formats. These formats will include some of the following functions:
Set a tag type (EPC classes, ISO, and so forth)
Read tag data
Write tag data (a number input in hexadecimal or ASCII format)
Print a label with data input by the user
Print a label with data read from the tag
Define EPC data structure
Specify the number of read and/or write attempts to a single tag
Verify the host computer/system
Set RF power for reading and writing
Set RFID tag password and other functions
You can also create label formats by using label software. Many printer manufacturers and software providers have developed easy-to-use software that will guide you through the label creation process and enable you to print and encode tags quickly and easily. This software will help you not only with basic EPC number encoding, but also with global trade item number (GTIN), serialized GTIN (SGTIN), serialized shipping container code (SSCC), and other data formats used in your supply chain. This is particularly important to the 40,000 suppliers of the DoD who do not have to pay the fees to join EPCglobal and get their numbers, but can use something called a Department of Defense address activity code (DoDAAC).
Some printers can be Extended Markup Language (XML) enabled, which increases their flexibility and interoperability with enterprise resource planning (ERP) systems. XML-enabled printers are able to print directly from common warehouse management systems (WMS), because the label formats can be directly uploaded by sending an XML data stream to a printer.