Facts About Data Matrix Codes for Product Identification (Part #1)
A data matrix code, or in short simply “DMC”, is a 2D code. In many industries DMCs have become the preferred way of encoding data, e.g. in automotive and medical industries. Machine readable data matrix codes are marked reliably, efficiently, permanently and abrasion-resistant with laser marking machines. But what do I need to know if I would like to mark products with data matrix codes?
What are the advantages of data matrix codes?
One of the biggest advantages: They need little space to store information. Furthermore, since data is redundantly encoded in the DMC, reading the information back from the DMC is possible, even when the DMC is partially impacted. That also contributes to the popularity and wide application of DMCs.
What is the Error Correcting Code (ECC)?
There are different error detection and error corrections methods related to DMCs, called error correct code (ECC). Nowadays the most common one is the ECC200. So typically, when you talk about DMCs, most people with some DMC knowledge will assume that you mean the DMCs with ECC200. Nevertheless, it makes sense to explicitly point out which DMC with which ECC you mean, especially prior to application tests, in order to avoid any misunderstandings with other people, because the selected ECC results in different looking DMCs. Look at the following illustration.
Despite the same content, the DMC looks different, depending on the ECC:
How can the size of a data matrix code be defined?
Another source of possible confusion is the size of the DMC, when there is no metric or clear reference mentioned nearby. You might hear from a colleague that he or she needs a 16×16 DMC on the product. Without any further explanation, that leaves room for interpretation, because the mentioned dimension “16×16” could refer to the requested area size (typically in mm) or symbol size (number of rows x number of columns) of the DMC. Does that make a difference?
Oh yes, it does. The following example shows how a DMC with symbol size 16×16 is marked on an area smaller than 16mm x 16mm (the right DMC below), while the other DMC on the left side with only a 14×14 symbol size covers an area of 16mm x 16mm.
(beware: both DMCs enlarged for better visibility, i.e. original area size of the left DMC was 16x16mm²; the proportional relationship between the two DMCs remained the same).
What is behind the symbol size of a DMC?
The symbol size determines the data capacity of a DMC. The larger the symbol size is, the more alphanumerical characters or numerical digits can be stored in the DMC. Beware that it also makes a difference for the symbol size, if you want to encode only digits or alphanumerical characters, i.e. a mix of letters and digits. In fact, you can encode more digits than alphanumerical characters in a DMC with the same symbol size.
The following two DMC examples illustrate that more data drives up the symbol size.
And the following table lists the most typically used symbol sizes and the related data capacity of the DMC.
Are there also rectangular data matrix codes?
When looking at the table, you might have asked yourself: “Wait a sec, a rectangle symbol size?” Yes, indeed. You can also create DMCs with a rectangle shape. In situations when you have limited vertical space for your DMCs, a rectangle DMC can the suitable approach to deal with that space restriction, as you can see below.
Does the surface structure have an impact on the readability of DMCs?
Complex surface structures are challenging regarding the readability of data matrix codes. Especially automobile parts often have rough surfaces with contours or changing dark shades. These are not the best conditions for a perfect machine-readable mark. That is where ultra high contrast black/white marking comes into play: This laser marking solution provides high readability of marked codes even on rough surfaces.
Laser marked data matrix codes on a brake caliper. On the left with optimized black/white marking, on the right without optimization.
Marking and reading of data matrix/2D codes in the automotive industry
The automotive industry is particularly committed to mark safety-relevant components permanently and perfectly readable to meet the requirements of product and process safety, traceability and quality management. Marked codes also have to be extremely resistant to abrasion, temperature, light and lubricants.
Laser markers are optimally suited to mark safety-relevant components and other automotive parts with codes because they mark permanently and highly-precise. Only precisely marked codes are reliably readable.
An efficient and practical solution for marking automotive parts are laser marking systems with integrated vision system which do not only mark but also validate the code and are capable of optical character verification (OCV). This vision-based marking process helps automotive manufacturers to achieve reliable traceability, highest product quality and process reliability all while lowering production cost per part.
Summary: 5 facts about data matrix codes
- You can have the DMC as a square or rectangle.
- The area size and symbol size of a DMC are two different things.
- The symbol size determines the data capacity of a DMC, or phrased the other way around, the amount of data to be encoded determines the symbol size of a DMC.
- The possible maximum amount of data in a DMC depends whether the data consists only of digits or of alphanumerical characters.
- Laser marking machines are optimally suited for marking data matrix codes on nearly every material, even on complex surface structures.