Rated Reading of dot-peened data matrix codes
Particulars in connection with the verification of dot-peened data matrix codes:
Needle-embossed codes are very frequently used in the automotive industry. However, the criteria and lighting scenario described in
the standard only work under ideal conditions (homogenous surface and low degree of roughness). But these ideal conditions are often
not present in the practice.
So what happens when dot-peened codes are applied to rough, reflective or rounded surfaces? As a result of the material, surface
properties, coating processes or other factors, the images of these codes generated according to the conditions of standard TR29158
cannot be depicted adequately and thus not be verified in a reproducible fashion.
For this reason, the code is devalued by the verification, even though it is perfectly embossed and readable in an absolutely reliable way.
How can this discrepancy be explained?
It is caused by the correlation between the lighting and the way in which the reflection of the light renders the code readable.
A dot-peened code carries its information in an embossed 3D structure, meaning that a contrast in the image is only created by
suitable lighting. In other words, the result of the verification is dependent in equal measure on the lighting and the quality
of the code. In turn, the quality of dot-peened codes can only be evaluated and verified properly if the captured image is clear.
But a sufficient image quality for the credible evaluation is only achieved if the arrangement of the camera and lighting matches
the embossed geometry.
Conclusion: It is essential to select the correct rather than the right angle!
Although the needle-embossed code is an extremely rugged and reliable method of identification, it is in some cases challenged because
of problems related to the verification practice. In the practice, the incorrect evaluations lead to discussions among the parties
involved in a supply chain, which should for all intents and purposes be avoided with the verification.
Our solution and recommendation: ”Rated reading” by means of the stationary reading systems DMR210 and DMR220
Aside from the decoding of the code content, special criteria are used for the qualification of needle-embossed codes. Among other
things, it involves the review of the homogeneity of the dots, that is, the uniform depth and positional accuracy of the dots within
the imaginary grid. For many applications it is additionally possible to detect the needle wear of the embosser by means of a defined
reference value and to issue a timely alert for the exchange of the embossing needle.
Our engaging white paper “Data matrix code verification in the practice” is available upon request.
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