Generally, the ribbon and labelling selection is the most often overlooked decision in a bar code system, labels peeling off, scanners unable to make good reads without several retries, or having a label that scratches or smears too easily. The ribbon and/or labels need to be suited to the environment and duration (life expectancy) of the label. Temperature, humidity, light, abrasion, chemicals, ageing, etc. will all affect the readability of the label.
Most users are familiar with dot matrix and laser technology. With dotmatrix printers, pin-fed labels are typically used and with laser printers, sheet-fed labels are used. However, when it comes to bar coding, not everyone is as familiar with direct thermal and thermal transfer printing. With direct thermal printing, the image is burned directly onto the paper and works similarly to a traditional fax machine with heat sensitive paper. With direct thermal printing, the image deteriorates with time. Thermal transfer printers require a ribbon which in turn is burned directly onto the facestock. Labels produced from thermal transfer will last much longer than labels generated from direct thermal transfer.
Paper labels are the most common and least expensive facestocks with thermal, dot matrix and laser printing. Paper facestock is best suited for indoor use and are a good product for labelling, material management, pricing, and shipping. Vinyl and polyolefin facestocks are strong and very resistant to smear and hot and cold temperatures. They are often recommended for labelling on curved or irregular surfaces or even underwater applications. Synthetic labels withstand more abuse the paper facestocks. They can resist moisture, oil, chemicals, and dirt. Polyester is extremely impervious to temperature, chemicals, and dirt. Polypropylene (such as Kimdura) tends to be more general purpose and less expensive material than polyester.
Thermal transfer ribbons consist of a protective back coat, a film, and ink. The back coat of the ribbon protects the printhead from abrasion and deposit buildup as well as dissipating heat from the printhead. As the heat rises from the printhead, the film provides a good thermal conductivity for the ink while at the same time prevents the ink from melting or smearing. The ink primarily consist of wax and resin properties. Wax based ribbons are predominantly general purpose and are the most economical. Wax and resin ribbons provide improved smudge resistance. These ribbons are priced substantially less than pure resins. Resin ribbons provide the most durable image currently available. These formulations generally require increased print head temperatures.
When purchasing both labels and ribbons, simple calculations can save both time and money. The length of a ribbon roll is generally proportional to the length of a label roll to minimise the number of times in changing out a ribbon. This "length" ratio is typically 2:1 but is not necessary. The length of the ribbon roll is usually given, but the same is not always true regarding the length of the label roll. Generally, only the number of labels per roll is printed. The approximate length of the label roll however can be calculated using the height (W x L) of the label, the number of labels/roll, and assuming that the space between the labels is approximately 0.125 inches. The following calculation can be made:
[ (L" + 0.125") x Labels/Roll] / 12