Bar codes have become indispensable in manufacturing, logistics and trade. They accelerate data collection, prevent input errors and even control entire systems. But this form of industrial automation only works if bar code scanners and cameras can read your bar codes without errors.
Weber Marking Systems provides its customers with all the right tools for product marking and coding: from label printers and barcode labels to labeling machines and inkjet printers. We therefore know the pitfalls of bar code readability and would like to share some tips for common causes of bar code failure.
For the reader to accurately recognize the beginning and end of the code, there must be a sufficiently large white area around each bar code – the so-called ‘quiet zone’. This area should be at least 5 times the width of the narrowest bar. Make sure that even subsequent finishing (e.g. film lamination) does not disturb the quiet zone.
High-contrast prints are easier to capture by scanners. Avoid light-coloured barcodes on light-coloured backgrounds and dark barcodes on dark backgrounds. Certain color combinations are also particularly unfavorable (e.g. red on white or black on blue). The best contrast is achieved with a black barcode on a white, non-transparent background.
Glossy materials such as lacquered cardboard, aluminum cans or film paper can affect readability, as they often do not optimally reflect the scanner's infrared light or diffuse it too much. Try the following trick: Print the barcode inverted by reversing the colors - instead of printing black lines, print white gaps.
If parts of the barcode are damaged, it is no longer readable by bar code scanners and cameras. Check your printing process: Direct thermal prints are not very durable as the label paper is sensitive to heat, abrasion and light. Thermal transfer direct prints are much more durable.
Furthermore, the printer itself can reduce the print quality if, for example, the nozzles and heating elements are dirty or damaged. Try cleaning or replacing the printhead.
Incidentally, a data matrix code is a little less complicated than the barcode: due to its high fault tolerance, it remains legible even if up to 30% of its code is damaged.
In some cases you will need to make sure your bar codes will be accepted by any other companies throughout the supply chain, maybe even all over the world. This means that your bar code images must meet certain rules that specify your bar code’s print quality, bar height, colour and background as well as its position on the label or packaging. Organizations such as GS1, which drive the global development and standardization of bar codes, provide according guidelines, tools and services.
First of all your bar code must not be (partially) obscured by any other objects during the scanning process. Also, you need to know that bar code readers have certain focal lengths that allow reading only within their reading distance range. Even the angle in which the reader is held in or mounted in can affect the readability. Therefore, make sure the bar code is easily accessible but also protected from dirt, buckling and any other damage risks.
Our tip: In order to identify many goods at the same time and without visual contact for scanning, RFID technology may be an alternative. The integrated RFID transponders in RFID labels are not only durable and robust, but also rewriteable.