Data Matrix Codes and Readability
September 19, 2007
When selecting where to place a 2D machine-readable Data Matrix code, engineers need to remember that it’s all about the data-ensuring it is readily accessible and easy to read. The location, for example, should be clearly visible throughout the manufacturing process, not just when the 2D code is being applied. Similarly, engineers need to be sure the surface of the part is conducive to easy reading and that the symbol location is not affected by shadows or any other type of interference.
Surface texture, in particular, can be a factor, especially when imprinting smaller codes. When working with rough surfaces, like those on castings, engineers may want to employ a more expensive laser marking system, as opposed to a less expensive dot-peen marker, to ensure the background texture won’t interfere with the symbol. Another option is to find or create a smooth region on the part and use that as the marking surface to promote readability.
In terms of curvature, the marking area doesn’t have to be perfectly flat. However, engineers need to be careful when working with rounded parts, because surface curvature can create distortions to the code that will make it difficult read. As a general rule, a code size that is no larger than 16 percent of the diameter of the curved surface, or 5 percent of the circumference of a cylindrical part, is acceptable. In cases where meeting these minimums becomes a challenge, engineers can do things like create a rectangular code of two stacked Data Matrix symbols, as opposed to using a single, large square-shaped symbol.
Again, it’s all about the data. Just because a ink-jet system, laser etcher, chemical etcher or dot-peen marker can create what appears to be a good symbol, that doesn’t mean it will be easy to read. With this in mind, engineers should always think about their marking needs before signing off on a component’s design.
“It should be treated like any other part of the manufacturing process. In [direct part marking] phrases like, ‘no place to mark, no room for marking equipment, no budget, no time to properly design-in the best method,’ are commonplace,” says Thomas Phipps, CEO of Columbia Marking Tools Inc. (Chesterfield, MI). “Marking is usually the last thing on the manufacturer’s mind.”
Bob Taplett, applications engineering manager at Microscan Systems Inc. (Renton, WA), agrees. “The earlier the better…. Designing marking and reading locations into the assembly line can save money, increase throughput and improve overall process control,” Taplett says.