Both carton and label ink jet printers spray dots of ink onto a surface to create text. Carton printers can place bar codes directly on containers. However, these symbols must be printed larger than other bar codes and may not be high in quality because the ink is often partly absorbed by the container material. Scanners must be adjusted for these conditions. Ink jet label printers, however, produce acceptable results.

Dot Matrix (In-House)

In dot matrix printing, pins or hammers impact a ribbon and transfer dots of ink to form characters. Bars are created from vertical columns of dots; wider bars are made by joining columns. Dot matrix printing is usually acceptable in quality, reliable, and low in cost.

However, dot matrix bar codes have a lower print density than some other forms of printing, and the printing equipment is noisier than many methods. Monitoring the age of the ribbon is especially important. New ribbons, full of ink, can produce wider bars than desired. As the ribbon is used, print quality improves and stabilizes. However, if the ribbon is not changed before it begins to wear out, the bars get narrower, lighter, begin to show breaks, and can become unreadable. Finally, the scanner beam must be adjusted to the width of the narrowest bar (usually one dot).

Drum and Formed Character (In-House)

Formed character printers include a rubber print wheel containing bars, letters, and numbers. Drum printers use a similarly configured drum. As the wheel or drum spins, a hammer mechanism strikes the wheel or drum against a ribbon and forces character images onto paper. This method allows more information to be included in a bar code in less space than most printing methods.

However, symbols are limited to the characters already on the wheel drum. Ribbons can be used only one time, and ribbons, facestock, wheels, and drums are expensive.

On the following page, a discussion of printing system considerations is provided. This information should help you identify some of the decisions you must make in implementing your bar code printing system.

Printing System Considerations

Stand-Alone vs. Computer-Driven Printing Systems

Stand-Alone Systems

Stand-alone systems do not require a host computer, which avoids any need to take a computer out of normal use to print labels. If your applications are well-defined and relatively consistent, such as compliance labeling for a long-term customer, a dedicated stand-alone system can work well. A stand-alone system housed in a sturdy case or cabinet may also be useful in an unprotected area or an industrial setting where a computer might be damaged.

Computer-Driven Systems

A computer-based printer must be linked to a host, such as a PC or a mid-range or mainframe system. This configuration may require more effort to install than a stand-alone unit. For example, if the computer serving the printer must be in an area where high temperature, humidity, or dust may be a problem, a sealed cabinet or room may be necessary. However, with the right software for your application, you can reduce manual data entry and connect label printing to your other systems to ensure accurate labels, invoicing, record-keeping, and so on.

Integrating a Computer-Driven Printer with Your Existing Computer System

Some computer-driven systems require a specific communications interface between the computer and the printer. Check carefully whether such an interface is needed-and whether your printer manufacturer or software package supplies one.

Printer Configuration

Consider the following options in choosing your printer:

Communications interfaces: You may need serial, parallel, coax, twinax, or others.

Memory: Your printer needs memory sufficient for your application and label software.

Print speed: You may need from 2-12 or more inches per second (ips). Throughput, a combination of print speed plus formatting time, is equally important.

Print head resolution: Resolution must be adequate for your application or the minimum standards of your customers or their industries.

Fonts: Fonts may be built-in or available on memory cards, computer chips, or cartridges.

Special media handling: You may need internal or external rewind functions, equipment to peel labels from their backing, label cutter, ribbon savers, or automatic label applicators.

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