Researchers at NASA's Marshall Space Flight Center (Huntsville, AL) have developed a way to read Data Matrix codes even if they are obscured by paint or coatings. The technique enables a scanner to read the 2D codes through as many as six layers of paint, or a total coating thickness of 15 mils.
The technique requires that the Data Matrix code be printed on the part with a magnetic material. A specially designed scanner can then read the code either optically or magnetically.
The magnetic marks can be read under conditions that would render optical methods useless. For example, the scanner can read the codes through contaminants, in the dark, or under bright light that would wash out conventional markings. In addition, assemblers can use the technology to deliberately hide Data Matrix codes for security reasons.
Supplied as a viscous ink or paste, the magnetic material can be applied to the part in one of two ways. First, the material can be printed through a stencil. Or, the 2D codes can be engraved onto the part with standard engraving methods, such as dot peening or laser etching. The magnetic material is then spread over and into the recessed patterns.
If the magnetic material is not strong enough to enable reliable reading over time, it can be magnetized again with a permanent magnet or electromagnet.
For more information on applying and reading magnetic Data Matrix codes, eInquiry 23.