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]

Let's conduct a simulated barcode read failure due to press gain.

Let's conduct a simulated barcode read failure due to press gain.

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

 

[Chief_1975]

If we where sending a file to printer who didn't specify their BWR spec and they where using Litho Offset (either sheet feed or web) then we would apply a BWR of 25 microns. For the litho printers we have worked with over the years who do specify BWR, the range has been 0 to 25 microns.

 

[Al Ferrari]

Thanks for the response Chief,

Let me double check my self on the math for microns: 1 micron is a millionth of an inch or .000001". So 25 microns is .000025". Correct?

The packaging printer I need to satisfy is asking for a BWR adjustment of -.002". By comparison, your 25 micron adjustment seems tinny. What software are you using to implement it? Does it apply the adjustment to an already generated bar code, or does it apply the adjustment on the fly as it generates the bar code?

Thanks,

Al

 

[gordo]

Let me double check my self on the math for microns: 1 micron is a millionth of an inch or .000001". So 25 microns is .000025". Correct?

25 microns is 0.00098 in - the width of a 2% halftone dot at 240 lpi or a 1% halftone dot at 120 lpi.

On a 2400 dpi devices that's two CtP pixels (one pixel being 10.6 microns). Put another way, you cannot make a BWR less than one pixel, i.e. 10.6 microns (0.00042") on a 2400 dpi device.

Best gordo

 

[Al Ferrari]

Thanks Gordon,

But I would have preferred having it pointed out to me that a micron is a millionth of a meter, and not of an inch. That would at least have given me credit for the "millionth" part. Try to catch me doing something right for a change. That's precisely why I started out that post saying I needed to check the math. I knew I had something cockeyed.

The other source of nagging doubt is that I had come across a barcode software company stating that
they took input for the BWR adjustment in microns, although I don't recall them saying how many of those they used.

I still would like to know what bar code software Chief uses.

Al

 

[meddington]

Supplying a number of packaging printers, I've seen litho BWR requirements ranging from .000" to -.004" (presumably based on substrate type, ink viscosity, impression, etc), with -.002" being the average. Generally BWR is defined at the stage of creation of the barcode.

 

[Al Ferrari]

Thanks Meddington,

So some packaging printers had no BWR required at all, and presumably they forego that based on a track record of no reported scanning errors at the retail checkout registers.

I am only after the facts here, and not justifying the practice.

While am at it, I see that no one has taken me up on my simulated gain test idea. I had hoped that it would engender a discussion leading to the realization that the printed barcode is only one cog in a complex structure involving the retailer's processing software that needs to have provision for appropriate the handling of faulty scans.

The liability side of the discussion so far was tending toward blaming the printer for the failure of the whole structure, in my view, the printer is only on the hook for the replacement of the faulty press run. Any packaging printer with a contract exposing them to more than that needs a new legal resource.

Al

 

[Bill W]

As a flexo printer we have to deal with, technical phrase, "alotta of squish" at press. Years ago we tested different BWR based by barcode size when printed on semi gloss stock with a waterbased varnish. We tested a version A code at 80%, 85%, 90%, 95% and 100% and felt that to best optimize the readability of a code we would apply a different BWR based on percentage.

FYI the BWR's are:

80% -35μ (.001379")
85% - 45μ (.001773)
90% - 60μ (.002364)
95% - 70μ (.002758)
100% - 20μ (.00394)

We use a software program (Barcoda) to create our codes which allows one to enter the BWR at code creation.

I have been with my employer for 27 years this summer, and the BWR test was done early in my career with them. As far as I know we have never had a barcode reject problem from either the CPC or the retail outlets that sell their products.

 

[Chief_1975]

I use Esko dynamic bar code plug-in for Illustrator, in past I have used Agamik which is stand alone program that creates a EPS file which can then be imported.

There lots other bar code software options out there, both stand alone and plugins for the various software applications, Indesign, Quark, Illustrator etc.

 

[Al Ferrari]

Thanks very much for the info.

Al

 

[jlee]

As a packaging printer we apply BWR on all barcodes regardless of printing process. They are however different based on print process, substrate and barcode direction (ladder or picket fence) in relation to press direction. One thing that is extremely frustrating is the fact that there is a significant difference in a barcode verifier vs a retail barcode scanner. All of our customers (primarily pharmaceutical) demand that we have verification reports that show ANSI grades of C or better, this can be an interesting challenge and I actually have a failure on my desk right now which is forcing me to reprint a job due to a barcode that is 1/1000th of an inch out of spec. The worst part is the fact that I can read the number correctly using a scanner, and I can read and decode the code on a verifier. But the verifier actually grades the barcode as a D due to a problem on BWR.

The scanners at the retail level are extremely forgiving, I've actually seen a package where the prepress operator slipped a decimal using 11.5 mil BWR when he should have used 1.15 mil which resulted in the strangest looking UPC style code I've ever seen. We took it to 5 different retailers with different systems and it scanned fine, but it was still out of customer tolerance.

So as much as I agree with you that in offset you don't really need BWR, the question really should be who do you have to satisfy, are you worried about scanning at the retailer level or do you need to meet an ANSI, ISO, GS1 grade requirement. If you need to meet a grade requirement BWR does have an impact. BTW My team also uses Esko dynamic barcode plug-in.