Medical Device Link.

PACKAGE CODING AND PRINTING

A microplotter film master verifier once used but no longer available. Photo courtesy of Quint Co.

In the 21st century, digital bar code images can be generated by anyone with a computer, some bar code software, and a little knowledge. Images of bar codes in various formats (e.g., EPS, BMP, TIFF) can be bought or even obtained free on-line.

The adage, ‘you get what you pay for’ is a warning to be heeded, especially when it comes to generating and using digital bar code masters in a CGMP environment. Not every digital bar code image is a bar code “master,” that is, a high-quality, first-generation bar code image (digital or otherwise) suitable for producing printing mats or plates and, ultimately, an accurate and reliably readable printed symbol. Because bar codes are nothing more than a series of varying-width bars or lines, it is critical that these bars be produced with precise widths and spacing.

Because small variations in the bar code image are inherently introduced during the intermediate and final production processes, the original image must compensate for these changes. In order to achieve the required modifications to the original image, producers must have knowledge of the symbology and extremely precise production methods. This critical issue must be clearly understood by those responsible for bar codes on FDA- regulated products.

Without the accuracy inherent in a true bar code master, high-quality printed symbols become significantly more difficult to achieve, no matter how good the intermediate procedures and processes may be. And high-quality printed symbols are a critical element in hospital efforts to improve patient safety through bar code–based medication administration systems. Unfortunately, the necessary education and strict SOPs required to produce a proper digital bar code master and to achieve consistent, high-quality printed bar codes on pharmaceutical and medical and surgical shelf-packs, unit doses, and units-of-use are not always present end-to-end in the packaging supply chain.

From the introduction of the Universal Product Code (UPC) 30 years ago until the mid 1990s, the only bar code master available was a film master. This was the original, first-generation bar code symbol imaged with a laser or other light source directly on film. During this same period, the only sources of bar code film masters were specialized companies that had invested in the specially programmed computers and vector photo-plotters necessary to make such high-precision images.

Beyond the obvious requirement that bar/space character patterns be correctly arranged to encode the desired message, the exacting requirement for bar/space width accuracy—i.e., ±0.0002 in.—was paramount. This requirement for accuracy has not changed, even with the use of digital codes.

This fundamental requirement has been spelled out for UPC symbols since they were first introduced. Two fundamental international standards cover all symbologies: ISO/IEC 15421:1999, Information technology–Automatic identification and data capture techniques–Bar code master test specifications; and ISO/IEC 15419:2001, Information technology–Automatic identification and data capture techniques–Bar code digital imaging and printing performance testing. These standards underpin the requirements for virtually all bar code masters (whether digital or physical).

In today’s digital, raster image– processing production environment, ISO/IEC 15419:2001 may be the more applicable standard. More specific to the needs of packaging and graphic designers, prepress technicians, and platemakers, the standard describes in detail the software design requirements for controlling indirect imaging devices such as image-setters, whether used to generate firstgeneration film, printing plates (direct-to-plate), or even final paper images.

ISO/IEC 15419:2001 discusses optimization of the X-dimension (width of the narrow bar/space) based on the resolution of the output device in order to ensure that every element has “an integer number of addressable dots consistently across all element widths.” Put plainly, this means that “arbitrary” rounding of bar/space widths by the image-setter must be avoided. Thus, this is something to be controlled by the bar code design software. In addition, the importance of Bar Width Compensation (often referred to as Bar Width Reduction, BWR) is discussed, as well as the unusual 1/13X “undersize” or “oversize” adjustment required for the “special EAN/UPC characters” that encode the digits 1, 2, 7, and 8.

When first-generation film (such as that used for traditional platemaking) is the product of the raster image– processing of a digital art file, the resulting bar code is the equivalent of a “film master.” Bar/space widths—and the requirement that they be rendered to the specified width ±0.0002 in.—should be assessed according to ISO/IEC 15421.

It may seem that these standards are intended for bar code software providers, not users. While this is true, they also provide users with insights on how to render digital bar codes and how to assess their quality.

Most importantly, bar code masters, whether digital or film, must be strictly controlled for dimensional accuracy, and their quality must be assessed at the earliest stage. Only in this way can fundamental problems with the original image be identified and corrected before incurring the time and expense of additional prepress and on-press work, the quality of which would be substandard, if not unacceptable, from the start.

For those who use digitally generated “vector art” bar codes—such as high-quality EPS (encapsulated postscript) files—it is still possible to take highly accurate measurements of individual bars and spaces and other relevant dimensions using the measuring tools inherent, for example, in Adobe Illustrator.

However, Illustrator only provides measurements to three decimal places. When the unit’s parameter is set to inches, three-decimal-place precision takes us only to thousandths of an inch (mils). This is not sufficient, as measurements in inches require four decimal places of precision (ten-thousandths of an inch) to accurately determine symbol quality.

The work-around for this is to set the Illustrator unit’s parameter to millimeters. Three decimal places of millimeters (one thousandth of a millimeter) is a micron. Since 25.4 µm equals 1 mil, measurements in millimeters give highly precise bar/space widths.

However, being able to measure bars and spaces is only the first step. Also essential is knowledge of which bar/space patterns are easiest to check and/or are most revealing for a given symbology and what the acceptable value ranges might be.

Fineline Technologies has recently introduced a product called SymArtDVT 2.0. The patent-pending SymArtDVT software is a plug-in for both Adobe Acrobat and Illustrator. DVT stands for Digital Verification Technology and according to the product manual, SymArtDVT “will identify, decode, and return bar/space characteristics such as the Narrow Bar Width, Ratios, Magnification, Quiet Zones, and Bar Width Adjustment.”

The product also provides the means to enter other relevant information to be associated with the symbol, such as company name, user name, and product description. This information, along with the date and time of the verification, can be saved to a disk and/or a report printed in hard-copy form.

SymArtDVT seems to be a significant advance toward the ultimate goal of automated quality assessment of digital bar codes at the prepress level, before printing plates are made or artwork is printed.

Though the product does not provide the ability to measure and report true Digital Decodability measured in accordance with ISO/IEC 15216, Fineline Technologies’ SymArtDVT appears to raise the level of digital bar code quality control.

For two decades, the production of bar code masters was the purview of the few specialists who had the knowledge, expertise, and sophisticated software and hardware necessary to produce them. Today, the digital-imaging revolution has provided the ability for almost anyone to generate bar code images.

Pharmaceutical and medical packaging managers, graphic arts professionals, and their packaging supply-chain vendors must therefore first understand the requirements and techniques for printing high-quality bar codes. They then must determine that the tools they have chosen or plan to use are capable of meeting these requirements. Finally, procedures must be developed and implemented to ensure that the desired outcome is achieved.

The combination of available bar code expertise, proven digital bar code generation software, and advanced digital bar code QA/measurement techniques and tools, when coupled with the necessary commitment, are sufficient to ensure consistently high-quality bar code masters.