TechArchive

Original article date: November 1997

Bar code systems are becoming more popular in all walks of life. Easy to use, they allow you to enter data much more quickly than by manual methods and they are very accurate. Their speed and accuracy improve many operations in manufacturing, including asset tracking, shipping, receiving and packaging.

Bar codes can be printed on a wide variety of materials. Consider the following when choosing a label material:

What are the reflective qualities of the material? The reflective property of the label is one factor that determines the diffuse return that is produced by the label.

What is the opacity of the label material? The label needs to be opaque enough so that the product to which the label is attached does not show through the label material and effect the readability of the bar code symbol.

What type of ink is used to print the bar code bars? The ink should have a very low reflectivity to provide maximum print contract with the base material. In addition, infra-red scanning devices require an ink material that is high in carbon content, while visible red scanners can function well with both regular and high carbon inks.

How durable does the label material need to be? If the label must withstand repeated contact readings, is a protective coating needed? Laminations greatly increase the ability of the label to withstand repeated contact readings.

A wide variety of adhesives can be used to attach the bar code label, including those resistant to high and low temperatures and those which allow the label to be removed or replaced. Tamper-resistant label adhesives make it harder to remove a label in one piece.

The decision to print bar code labels on-site or purchase them from an outside vendor depends on the application. On-site printing offers most flexibility to change label information. This can be very beneficial if you regularly add products or need a variety of different labels in small quantities. Keep in mind that if you choose to print your own labels, you are responsible for the print quality. The printer type must be considered also.

Off-site printing is most advantageous for high volume applications and when bar code data variations are minimal. Also, print quality is the vendor’s responsibility. Print costs vary, depending on the application, so the vendor must be advised in advance of precise application requirements.

There are three categories of bar code printing software: pre-written (canned), customised and user-written.

Most pre-written packages provide user-friendly icons and WYSIWYG screens, requiring very little software background. They can reduce bar code system setup time and cost, at the expense of the label design being a pre-defined format. Pre-written packages support the major linear symbologies. The most common host is a PC.

Customised software packages are popular with users who have specific label design requirements. Packages are provided by software suppliers and hardware manufacturers. Typically, they consist of a printer-resident graphics controller and a bar code/graphics programming language.

Using templates and tools, bar code labels can be designed to meet specific application requirements and modified if changes are needed. Software packages may be standalone programs or embedded in larger document printing systems. Complex labels and forms may require outside programming assistance.

User-written software is the most costly and complex approach to bar code printing. The programmer must have an in-depth knowledge of the printer, interfaces and standards for the symbologies required. Configuring the bar code printing system, writing the software and testing the labels must be taken into consideration as well.

A free, 90-page book available from Rockwell Automation informs of the basics of bar code technology, including symbologies, printing, products and applications.

• Rockwell Automation
• Jennie Holmes
• Tel: 01908 838830

November 1997