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This article provides an overview of some of the problems and difficulties experienced by customers using bar code systems, particularly those incorporating EAN, UPC and ITF symbologies. If you have a specific question, please feel free to contact us.

Choosing the Correct Bar Code

 Verification

 Printing Bar Codes

 Common Printing Problems

Colour Combinations for Bar Code Reproduction

Choosing the Correct Barcode

There are six different symbols that are commonly used to represent the article number on a product, and these are shown below.

EAN-8	UPC-E
EAN-13	UPC-A
ITF-14

Any item that can be sold at a retail point of sale must be marked with an EAN-13 or UPC-A symbol (or EAN-8 / UPC-E if the product is small enough), as these symbols are designed to be scanned omni-directionally, which helps to speed up checkout procedures.

The EAN-13 and UPC-A symbols can also be used to identify any other items that will not cross a retail point of sale, but many companies find that using ITF-14 or UCC/EAN-128 symbols easier. ITF-14 symbols were originally designed to be allow bar codes to be printed directly onto fibreboard outer cases, as they are simpler and larger bar codes than EAN-13 symbols.

UCC/EAN-128 symbols were introduced in 1989, and allow companies to provide extra information, such as expiry dates and batch numbers, alongside the identifying article number. They cannot be used to replace EAN-13 and UPC-A symbols on items that will be sold at a retail point of sale, but can be used to mark all other trade items. All the data shown in these bar codes has to be specified by EAN's application identifier standard, and because they can include constantly varying information such as best before dates, or serial numbers, they will usually be printed on-line using labels. These symbols are in use through out the supply chain as they enable organisations to automate their tracking and traceability systems.

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Verification

With bar coding becoming more important at all stages of the supply chain, users often ask for a means of checking bar codes for scannability and accurate decoding. Test scanning only provides a pass or fail answer, so verification has been used to give an indication of bar code quality.

The ISO standard will qualify bar codes using both the ANSI and CEN grades, and these are shown below:

Numeric Range (CEN)	Alphabetic Grade (ANSI)
3.5 to 4.0	A
2.5 to 3.5	B
1.5 to 2.5	C
0.5 to 1.5	D
Below 0.5	F

Symbols graded 3.5 or better will perform more reliably and should be specified when the scanning beam crosses the symbol only once with little possibility of re-scanning in the event of failure. Between 2.5 and 3.5 may require scanning more than once. A grade between 1.5 and 2.5 indicates that the bar code is likely to need more re-scanning, and should only be used in systems where multiple scanning is automatic, or where users are prepared for re-scans. Those symbols graded between 0.5 and 1.5 may fail to read at all on some systems. Symbols graded below 0.5 are unlikely to perform reliably with any equipment.

With any bar code printing, and especially on-demand labelling processes, it is vital to check that the symbols are scannable, and verification is the best means of testing symbols at the start of a production run and at regular intervals.

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Printing Barcodes

The size of a bar code will be determined by the printing process, the inks and the substrates being used. The aim is to produce a scannable bar code symbol, and its size will generally need to be increased as the quality of materials falls. Printers can carry out tests using printability gauges that will determine the size of the symbol, and how much adjustment to make to the width of the bars to accommodate any ink spread.

Some companies will use film masters as the master image of a bar code. This is the conventional method, which has been in use since the 1970s and enables users to have an image accurate to five thousandths of a millimetre. Provided the correct adjustments have been made for the printing process and materials, film masters provide a very precise starting point for producing good quality symbols.

With the increase in use of computerised graphics, more and more companies are using integrated software packages to create images of bar codes as part of the packaging design, and these, used correctly, can produce good symbols. The software and hardware involved should be examined to ensure that the resolution of the system allows for accurate adjustment of the bars and spaces.

There are many ways of producing bar code symbols, and on-demand label printing equipment is often used when creating UCC/EAN-128 bar codes to provide variable information, such as batch numbers and best before dates. Labels are also used to identify small runs of a particular product, for example potted plants in a garden centre, when there is no extra packaging.

Temperature sensitive labels, such as thermal labels, should be used with care, because if the product is subjected to high temperatures in its environment, the labels may turn completely black. Sunshine may have this effect on these labels and render them unscannable. Other labelling techniques, such as thermal transfer, may provide more robust labels, and each user will have to determine the best technique to use.

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Common Printing Problems

These are some of the common problems encountered. All of these can be avoided if sufficient care is taken at the design and origination stages, and the correct use of verification equipment.

Poor quality substrates would result in a loss of quality, often greater ink spread, or the appearance of print defects. Darker coloured substrates could result in insufficient contrast when scanning the bar code.

Choosing incorrect colour combinations which will not scan. Choosing metallic inks for bars or background is also not recommended due to specular reflectance. Reversed out images, where the bars are white against a coloured background are also non-scannable.

Choosing incorrect colour combinations which will not scan. Choosing metallic inks for bars or background is also not recommended due to specular reflectance. Reversed out images, where the bars are white against a coloured background are also non-scannable.

Using transparent substrates, and hoping that the container will provide a suitable background colour for either the bars or spaces is not recommended.

Using uncovered metal surfaces as a background or for the bars. The high reflectance of the substrate can cause problems and a solid background colour should be printed to provide good contrast.

Some bar codes require light margins, and if these are not large enough the printed symbol will not be in spec. The UPC-E, EAN-8, UPC-A, EAN-13 and ITF-14 symbols for example have physical indicators, but UCC/EAN-128 has no light margin indicator so extra care must be taken.

Printing bar codes that are either too small or too large to be read by scanning equipment.

While some problems with bar codes will be found after verification, many others are discovered only once labelled products have reached customers, causing further problems. Some companies may even fine their suppliers for the disruption caused by any problems with bar codes, so it is always worth giving particular attention to the production of good symbols. Apart from the quality of the printed bar code, there are other aspects that need to be checked.

Are any bar codes on individual items visible when they are packed into outer cases or cartons? If they are, there can be problems if the bar code on an individual item is scanned by mistake instead of the one on the outer case.

Are there any extra labels, sealing tape, straps, shrink wrap or other additions obscuring the bar codes? The unit, as it leaves to go to the customer should be checked to ensure the bar codes are clearly visible and scannable.

In the case of print-and-apply, are the on-demand labels being correctly applied, so that the bar codes are not too close to the corners of the cases? Are the labels being applied in the correct orientation, and without being creased?

Will the product be kept in a hot or cold environment, and will the labels be affected?

Are the article numbers of new products being notified to trading partners well before they are first delivered? This period may be at least three weeks, and the notification should be in a form agreed by the companies concerned.

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Colour Combinations for Barcode Reproduction

While black bars on a white background provide a very good image for scanning, other colours can be used. Scanners use red light which means that the bars must appear clearly under it. Cold colours such as blue and green can be used for the bars, but warm colours such as yellow, orange and red can only be used as background colours. Metallic colours should be avoided, for both bars and background, due to specular reflectance which disrupts the scanning beam.

The examples shown are of both good and bad colour combinations, and tests should always be carried out if unusual colours are to be used. It is not always necessary to introduce black as an extra colour if the existing colours can provide a scannable combination. It is also important that the bars are printed using a solid colour, and not using a four colour process.

Acceptable Colour Combinations

Black on grey	Black on orange	Black on yellow
Green on white	Green on red	Green on orange
Green on yellow	Blue on white	Blue on orange
Blue on yellow	Purple on white	Purple on red

Non-Acceptable Colour Combinations

White on blue	White on orange	White on red
White on black	Orange on white	Orange on purple
Orange on green	Orange on blue	Red on white
Red on pink	Red on orange	Red on yellow

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