Barcodes on Corrugated: A deeper Look
The verification report is a powerful tool in printing barcodes on corrugated—it doesn’t just tell you if something is wrong. It points you toward what is wrong and from your experience in your trade, helps you figure out what to do to improve results.
Barcodes on Corrugated typically grade poorly for Symbol Contrast
This is a typical GTIN-14 with an.040” X dimension (narrow bar or space) on bare corrugate and here is its verification report.
Somewhere on every verification report for an ISO compliant verifier, there will be a place where you can find the final grade. On this report it is just beneath the decode on the Summary (left) panel near the top. This symbol earned a D grade–not unusul for barcodes on corrugated. This is the average of ten scans (see Display Scan at top left).
This is a GTIN-14 (ITF) with a .040” X dimension (narrow bar).
The Details panel on the right shows the grade for each of the eight tested parameters. In the ISO system, the lowest graded parameter is the Scan grade: look for the parameter that drove this grade down to a D. No surprise—it’s the parameter Symbol Contrast; typical for bare corrugated.
Here’s a symbol of identical size—same .040” X dimension, same defects grade, same modulation, same edge contrast, but printed against a white drop-out.
White background dramatically improves contrast for barcodes on corrugated
Note that the decode is different: it’s not the exact same barcode but the parameters grade almost identically, except for symbol contrast. What a difference the white background makes!
Here’s another bare corrugated situation with a very different barcode, a Code 39 with a .017” X dimension.
As you’d expect, the symbol contrast is a driving the final grade to a D—but so is the parameter Decodability—and the parameter Decode is an F. What’s happening here?
Because symbol contrast is so common in barcodes on corrugated, it’s easy to overlook other more serious problems.
This report points to a structural problem with this barcode, signaled by the red alert field in the report. Some, but not all, verification report applications help the user to understand report findings. By clicking on the word “Structure” associated with the Error message in the Summary panel, a pop-up window stating “unexpected start/stop”.
This directs you to the tab “Encodation” in the Details panel, which shows the problem—redundant start/stop patterns in the Code 39 (notice the encodation displayed at the top of the Details panel).
Not all verification reports are this helpful—Axicon is one of the best.
Finally, let look more closely at the parameter Decodability. This is probably the second most prevalent problem with barcodes on corrugated. We’ll examine the exact same barcode achieving very different verification results.
The verification reports point to Decodability as the parameter driving the low final grade—in addition to the low Symbol Contrast that was already a factor.
Decodability problems can be a challenge to diagnose with barcodes on corrugated
Decodability measures and grades the widths of bars and spaces in comparison to their nominal or “perfect” values. Decodability evaluates the amount of tolerance remaining after the printing process.
If all the tolerance is used (the bars or spaces are at their maximum plus or minus range) the decodability parameter will be downgraded.
Decodability problems aren’t necessarily a simple press gain problem. Grading is also impacted by unevenness in the impression, where elements which should have the same width such as narrow bars are not, for some reason, all the same.
Decodability will also signal if elements—bars or spaces—do not fall in their proper positions. Often this is due to barcode design software problems or incompatibilities with the printing process.
Your comments or suggestions about barcodes on corrugate are always welcome.