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FLEXO Magazine : September 2010
Technologies & Techniques New High Density Bar Codes Challenges and opportunities for Flexo Printers By glenn spitz New bar codes, such as GS1 DataBar and Data Matrix, are beginning to show up on consumer items, on flexible packag- ing, and present new challenges to flexo printers. In some cases, the feature sizes of the new bar codes are smaller than the traditional UPC codes. Also, the tolerances can be tighter, making it more critical than ever to understand the print qual- ity requirements for these bar codes and how to meet them. This article aims to give flexo printers the information nec- essary to be as successful with new high density bar codes as they are currently with UPC symbols. Readers will be introduced to the structure of these new bar codes, and learn how they are both similar to and different from UPC symbols. In addition, this article will explain ISO grading parameters used to measure the print quality of these bar codes and introduce some terminology necessary to discuss these new types of bar codes with customers, suppliers and between prepress and production departments. HigH DeNsity Bar CoDes You don’t have to look far to find a new and possibly unfamil- iar type of bar code in the world of packaging today. And many of these bar codes are printed in high volume using flexo. A short trip to any supermarket or grocery store will reveal a stacked bar code on fresh fruit items (see Figure 1). One reason that these bar codes are being used on pro- duce as opposed to regular UPC codes is that the small size of the GS1-DataBar can be printed and read. The bar code can fit on a small label—one that can adhere to the curved surface of a fruit and not fall off. But it is the same small size that makes it attractive, as well as presents challenges to the flexo printer. Another related type of bar code is used on a new type of coupon. Called GS1-DataBar Expanded, it can consist of multiple rows (typically two, but sometimes three or four) and allows enough information to be encoded for a complex offer to be expressed on a coupon. A typical offer may be that you get one item free if you buy two other items. The marketing imagination has brought these coupons out of the Sunday newspaper, and onto the labels of many packages that the consumer would ordinarily throw away. What better way to make a tie-in to a product your customer already buys by promoting a related product on the disposable packaging? The third type of new bar code is Data Matrix. This type of bar code, shown in Figure 3, is truly a different animal. Rather than composed of bars and spaces that vary in width in order to convey encoded information, these matrix codes consist of an array of square cells, each representing a 1 or a 0. Data Matrix is actually only one type of matrix symbol- ogy. Others include QR Code and Aztec Code. This article will discuss only Data Matrix as a generic example of these types of bar codes. While the stacked multi-row bar codes in Figure 1 and 2 consists of several rows, the matrix symbol in Figure 3 consists of multiple rows and columns. If a multi-row sym- bol is printed with the web, you would minimize bounce, but what does it even mean to print a matrix symbol with or against the web? In the extreme case of a single cell that is not bordered by other cells, you have a small square that stands on its own on a print- ing plate. Data Matrix is typically printed in a square arrange- ment (number of rows equal to the number of columns of cells). The size of the square matrix grows as the amount of data, and therefore, the number of cells needed to encode all those 1’s and 0’s increases. For some label designs, however, a rectangular shape accommodates the available space better. An 8 x 32 cell matrix is shown in Figure 4. Figure 1. gs1-DataBar stacked omnidirectional bar code commonly found on fresh produce. All images courtesy Webscan inc. Versions of GS1 DataBar • GS1 DataBar Omnidirectional. A single-row version, tall enough for point-of-sale scanners. • GS1 DataBar Omnidirectional Stacked. Two rows, tall enough for point-of-sale scanners. • GS1 DataBar Truncated. A single-row version, shorter, not for point-of-sale, often used on pharma- ceuticals • GS1 DataBar Stacked. A two-row version, shorter, not for point-of-sale, often used on pharmaceuticals • GS1 DataBar Limited. A very short, one-row version, not for point-of-sale, often used on pharmaceuticals • GS1 DataBar Expanded. A single-row, but variable length version, used to encode extra information about an item, such as expiration dates. • GS1 DataBar Expanded Stacked. A multi-row, variable-length version, used for coupons and other applications using extra information such as expira- tion dates. 50 FLeXO sePtemBer 2010 www.flexography.org FLX_Sept2010_mech.indd 50 9/1/10 9:45 AM