Moving to another dimension

WHEN TWO-DIMENSIONAL MATRIX CODES were first launched commercially, many people saw them as a solution looking for a problem; one-dimensional barcodes were adequate for most needs and, at the time, few people appreciated the benefit of the data density that could be achieved with 2D matrix codes.

Another problem with 2D codes was that, as so often happens with 'new' technologies, there were almost as many 'standards' as there were suppliers. Which ones would turn out to be the best bet in the long-run, and which should be avoided? No wonder the initial take-up was slow.

But times have changed and there is now a more widely-recognised need for components and assemblies to be encoded with more data for reasons of traceability - especially in the automotive sector where product recalls are so costly and widely publicised (witness BMW's embarrassing recall of 500 new Minis). In a 2D code taking less space than would be required for a barcode carrying a fraction of the data, manufacturers can encode a serial number, date and time of manufacture, in-process inspection results, and much more besides. As time has passed, certain code standards have also started to emerge as leaders in their respective markets, reducing the risk for the engineer who has to decide which one to choose.

Depending on the requirements, 2D codes can be printed by inkjet, rapid indent marking or laser. In the main, inkjet is used in the food and drink industry, rapid indent marking is used in automotive, aerospace and general engineering, and the use of laser is widespread for marking plastics, pharmaceutical products, and where miniaturised marking is required. But the beauty of all of these techniques is that they can print on demand, so the individual code can be generated when it is required to be applied to a specific component or assembly. Perfect for a production line that is properly networked.

No designer worth his salt would issue a drawing for manufacture without it being checked and, similarly, no code should be applied without the means to verify it. Verification not only ensures that the correct code has been applied, but also that the code has been printed legibly. However, while a barcode can be easily and cheaply read by a fixed or handheld scanner (and often the human-readable alphanumeric code is printed as well), 2D codes require greater sophistication.

The only feasible way to verify a 2D code is to use a vision system, making use of suitable software that can process the image, interpret the code and cross-check it with what should have been printed. Thankfully, in the time that it has taken for 2D codes to become more widely accepted, 'smart' cameras (with built-in image processing and intelligence) have also been developed to the level where they are little more than highly sophisticated bolt-on sensors. And networkable too. So a manufacturing plant can readily incorporate component and assembly marking and verification, with all of the control and data acquisition maintained centrally.

Another benefit of using an intelligent verification system is that it can also monitor the quality of the marking process, so an alarm can be raised if the quality starts to deteriorate and action taken before illegible codes are printed.

Don't get the wrong idea, barcodes are not obsolete. 2D codes will never be as low-cost and simple to implement as barcodes, and many applications will never justify the cost and complexity of a 2D system. Barcodes are here to stay. But before you make an investment, look to the future: consider what demands your customers may be making of you next year in terms of traceability. Adding that second dimension to your codes may save you money in the long-run.