Barcode Quality in Prepress

 In 301

Apologies to those of you for whom this is all review—it may be news to others.

Barcode Quality begins way before the press

Barcode quality isn’t just a printing issue—it begins in prepress.  Every step in the process is an opportunity to influence the quality of the printed barcode; every step is also an opportunity to test and track the quality of the barcode.

Recently I followed a barcode through each prepress step in a flexo printing facility. The barcode design file was supplied to them by their customer—not always the best practice but neither is it unusual.

Barcode Quality is a step by step process

This shop always verifies the barcodes at pre-flight and did it on this job. The UPC was pretty much what they always expected—it earned a B grade because of 51% Decodability, probably because the 100% magnification UPC symbol had an Average Bar Gain of -15%  from a tolerance of a possible +30.5% or 0.002” off a tolerance of 0.004”.

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Nothing unusual for pre-flight since the symbol hadn’t yet seen any of the press gain for which it had been compensated.

The job proceeded as normal, and the barcode quality was again tested on the Epson proof just before going to press. The Epson proof had an Average Bar Gain of -20% of a possible +30.1%, or -0.0026” from a tolerance of +0.0039”. But now the symbol was at 99% magnification because the proof had also been distorted to compensate the flexo plate.

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It was a bit concerning but the bar width reduced symbol still hadn’t seen any press gain.

Every step can affect barcode quality–but do you know how?

Still feeling pretty confident, the symbol, along with the consumer packaging graphics, went to press. Everything was adjusted properly and the first finished labels started rolling out. The barcode quality was even worse. It was nearly failing the Decodability parameter at 27%; it had used -31% of a ­+30.1% tolerance, or -.004” or a ­+.0039” tolerance.  The symbol was still at 99% magnification.

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Now everybody was confused. What had happened?

Actually, that’s exactly the right question. What had happened? There were so many variables in the process—a process that had worked perfectly for longer than anybody could remember—what was different?

But none of those step-by-step processes had ever been documented over time, so there was no known trajectory of barcode behavior at pre-flight or proofing. The barcode was still an unknown by the time it reached the press. In actual fact, the barcode was an unknown when it arrived as a graphics file from the customer: nobody had any idea whether it had been bar width reduced, let alone by how much.

After some discussion, it was also learned that changes had been made in the plating process; the new digital plates seemed sharper, and the printed barcodes were now coming off the press thinner.

Documenting the quality of the barcode each prepress step, job after job, month after month, builds a valuable database of information.

Such a database forces you to identify each step in the process, and smoke out all the variables. Once that’s done, a change to any one variable becomes obvious.

A step-by-step process database puts into your hands the tools to control and predict barcode quality. Over time you create a knowledge base from which comes success and confidence.

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