Barcode BWR adjustment

[Al Ferrari]

Is anyone working in packaging and implementing a BWR adjustment on barcodes to be printed exclusively by sheetfed offset?

It seems that in offset this adjustment is not really needed because the press gain is not significant and with modern direct to plate methods there if no gain in the platemaking. So that the adjustment addresses a liability issue and not a technical one.

Al

[Edit] for those who may follow this from the sidelines: BWR stands for Bar Width Reduction.

[gordo]

Basically a BWR adjustment is a compensation for "dot gain" - actually the spread of ink in the presswork that could cause the bars (rather than halftone dots) in a barcode to be unreadable. This is obviously much more of an issue with flexo than with offset. And as you said, this is more of a liability issue with them rather that a technical one since fines can be imposed if the bar fails to be read.

Because BWR compensates for ink spread, it is process and media dependent even with offset. I.e. print the barcode on an absorbent substrate and you'll get a different result than if you print on coated. The best method for determining whether you need the BRW adjustment is to measure it. You start with a barcode graphics file with no BWR. The uncompensated width of a guard bar on a UPC symbol at 100% magnification is 0.33 mm/.0130”. Measure the width of the printed guard bars using a microscope with a measurement grid (reticule). Any deviation from .0130” will let you calculate the correct amount of bar width reduction for that ink and substrate combination.
You can either run a dedicated test on the actual stock, or you can run the test on off cuts of live jobs.

Some shops keep records of how the barcode gains on different substrates so as to not have to continually retest.

best, gordo

[Al Ferrari]

Thanks for the response Gordon,

All of this I already knew and your comments are well taken, but what do you mean by "since fines can be imposed if the bar fails to be read"?

What does the creation of a press sheet layout by imposition methods have to do with this? Or are you saying that the possible spread might be different toward the edges of the press sheet than at the center?

I would like to get comments from others who actually work in shops where this adjustment is either actually implemented, or has been considered and rejected as not applicable to their method of production.

Al

[gordo]

Thanks for the response Gordon,

All of this I already knew and your comments are well taken, but what do you mean by "since fines can be imposed if the bar fails to be read"?

What does the creation of a press sheet layout by imposition methods have to do with this? Or are you saying that the possible spread might be different toward the edges of the press sheet than at the center?

I would like to get comments from others who actually work in shops where this adjustment is either actually implemented, or has been considered and rejected as not applicable to their method of production.

Al

Different meaning of "imposed". If the Barcode fails to be readable the retailer may be fined and as a result there could be ramifications with the brand owner (cpc). And as a result you may end up in trouble. Click here for a good synopsis http://www.ehow.com/about_5376451_upc-scanner-laws.html

The shop where I worked did packaging work using offset and did not have to apply BWR. The package substrates were either coated papers or plastic. But, like I said, on a different substrate that may not be true. That's why it's best to check/measure on the substrate you'll be using. Better safe than sorry.

Best, gordo

[Al Ferrari]

Finally a response relevant to my question!

So in a certain shop, where barcodes where printed on coated paper by the offset method, the adjustment was determined not to be needed. And this is reported by the same person that explained how to measure the barcodes. This is indeed the information I am looking for.

Thanks Gordon.

Can any one else please contribute their experience?

But regarding the link to the ehow article, that is of extremely limited value here, since it focuses only on the price charged for the article carrying the faulty code. The code does not necessarily contain the item's price, but simply an ID number which the store's system associates with a price in its database. A miss read can simply result in the item being recognized as a different item, or more likely result in the item not being recognized at all.

Al

[Edit] RE: Different meaning of "imposed": I now see that I miss took "fines" for "files."

[gordo]

Finally a response relevant to my question!

So in a certain shop, where barcodes where printed on coated paper by the offset method, the adjustment was determined not to be needed. And this is reported by the same person that explained how to measure the barcodes. This is indeed the information I am looking for.

Yes. I just didn't want to make an absolute statement when I didn't have all the info - I.e. your print condition. That's why I told you how to determine it for yourself.

The enow article link was just to give you a heads up that there may be a liability if there are problems at the retail level reading the barcodes you printed. I think the risk is extremely remote, but it's best to be aware.

Just a thought. I wonder if you could use a bar code reader app for iOS to check that your barcode is working?

Best gordo

[Al Ferrari]

1. Take a barcode into Illustrator to effect the simulation.

2. If it is a font based bar code convert it to outlines.

3. If it is already vector objects, proceed to the next step.

4. Create 10 copies of the vector objects 1 inch apart.

5. One by one, for each set, center line stroke the bars with a black stroke increasing the stroke from 0" to .009" increasing the stroke amount by .001 for each successive set. This produces 10 sets with a Bar Width Gain ranging from none to .009".

6. Save the file as a press quality pdf and print it by offset to proper density on coated paper.

7. Read each of the barcodes with a calibrated reader.

What would be the results? What happens when the codes fail to read?

Al

[arkay_desai]

Hi Ferrari,
BWR is not really required when you are working with offset. here some more articles about BWR for your reference.
I used Barcode X software to create bar codes and never used BWR.
Bar Width Reduction
Bar Width Reduction � BARCODE-TEST
Bar Width Reduction Part II

[Al Ferrari]

Hello Arkay,

Thank you for the response and particularly for the links.

Al

[Al Ferrari]

Do we have any documented cases of Press Gain based barcode read failures resulting in a wrong item ID, as opposed to a no item ID at all?

Al