Edge factor, Dot void factor, Slur factor

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Edge factor, Dot void factor, Slur factor

Postby grarom-va » Fri Oct 25, 2013 8:36 am

These are terms i met in some brochure for a optical measurements device for flexo. Anybody can explain what exactly do they mean since i wasn't able to find relevant explanation on the web. Thanks!
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Re: Edge factor, Dot void factor, Slur factor

Postby Frank Burgos » Thu Oct 31, 2013 12:36 pm

Hi grarom-va,

I see folks have viewed this post, but none, including myself, have responded. I can guess at what is meant by those terms, but I have never heard them used.

Can you put up a scan of the brochure, or point us to it on the web?

Regards,
Frank
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Re: Edge factor, Dot void factor, Slur factor

Postby grarom-va » Fri Nov 01, 2013 7:29 am

Frank Burgos wrote:Hi grarom-va,

I see folks have viewed this post, but none, including myself, have responded. I can guess at what is meant by those terms, but I have never heard them used.

Can you put up a scan of the brochure, or point us to it on the web?

Regards,
Frank


Hi Frank,

There are a few brochures selling aprox the same product like the one i'm supposed to translate the brochure for:

http://www.teamflexo.com/products/betaflex335.asp

http://www.betascreen.com/betaflex334-brochure.pdf

http://www.peret.it/images/stories/pdf/FlexPro-2012.pdf

http://www.xrite.com/documents/literature/en/L7-442_vipFLEX2_en.pdf

If you are interested, i posted the same question on a few groups on LinkedIn and got a few answers here and there. I send you a connection request in order to be easier for you to see the groups and the discussions.

Thanks for trying to help!
Best regards!
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Re: Edge factor, Dot void factor, Slur factor

Postby Frank Burgos » Fri Nov 01, 2013 7:58 am

You're very welcome, Vasile. I'll have a look at the links and let you know if I have anything to add.

Have a nice weekend!

Frank
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Re: Edge factor, Dot void factor, Slur factor

Postby Frank Burgos » Fri Nov 01, 2013 7:58 am

You're very welcome, Vasile. I'll have a look at the links and let you know if I have anything to add.

Have a nice weekend!

Frank
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Re: Edge factor, Dot void factor, Slur factor

Postby grarom-va » Fri Nov 01, 2013 8:28 am

Frank Burgos wrote:You're very welcome, Vasile. I'll have a look at the links and let you know if I have anything to add.

Have a nice weekend!

Frank


OK

You too have a nice weekend! (but it's only friday morning over there, if i'm not mistaken) (hence the double post before coffee, i guess :-P)

Best regards!
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Re: Edge factor, Dot void factor, Slur factor

Postby Frank Burgos » Fri Nov 01, 2013 8:46 am

As soon as I get back to my office, I'll have a third cup! :)
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Re: Edge factor, Dot void factor, Slur factor

Postby Frank Burgos » Tue Nov 05, 2013 11:44 am

I just sent a note to my buddy, Larry Goldberg, at Beta. He might be able to shed some light.
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Re: Edge factor, Dot void factor, Slur factor

Postby ljgoldberg » Tue Nov 05, 2013 2:39 pm

Hello fellow flexo guys,

I'm sorry about my delay in replying to the original question.

"EDGE FACTOR, DOT VOID FACTOR, and SLUR FACTOR: These are terms I met in some brochure for a optical measurements device for flexo. Anybody can explain what exactly do they mean since i wasn't able to find relevant explanation on the web. Thanks!"

These three parameters are used in the current Betaflex PRO and earlier flexo analyzer models.

EDGE FACTOR is the ratio of the average path length around the dots in the sample to the path length around a theoretical, perfectly round dot of precisely the same dot area and screen ruling. The LOWER the better. Typical, "nice looking" round dots between 10% and 40% will have an EDGE FACTOR of about 120. This means they have 20% more edge length than a perfect round dot. Ideally the value would be 100, but the imager in the Betaflex cannot produce perfect round circles, always creating a microscopic amount of stair-stepping, hence a low, but not zero amount of excess edge length.

The thinking behind this comes from the world of litho, where trouble starts at the edge of the dot, rather than the center. A dot with a lot of fine detail around the edge will produce more dot gain for a small mechanical problem such as slur than would the same size dot produced as a perfect circle. There’s nothing to worry about unless the value becomes quite high, around 150 or so. Except if you are running KODAK Flexcel plates. The high resolution imaging of these plates produces very high EDGE FACTOR results, but they seem to print well when setup properly.

DOT VOID FACTOR is tech-speak for donuts, or more precisely the holes in the donuts, the interior portion of a flexo printed dot that carries almost no ink. I tried to convince the programmer that everyone in flexo understands what donuts mean, but he insisted on a proper technical name, hence DOT VOID FACTOR. It is the ratio of the area of the donut hole to the total area of the dot. Do NOT simply subtract the DOT VOID FACTOR from the Dot Area; you may end up with a negative number! If the Dot area of the print sample is 25% and the DOT VOID FACTOR is 10% you need to calculate what 10% of 25% is. The answer is 2.5%, meaning that the effective dot area is actually 25 – 2.5 = 22.5. Don’t forget that the Betaflex measures TRUE MECHANICAL DOT AREA which is different than the dot are calculated by your densitometer using the Murray-Davies formula. This gives excellent correlation to the measured plate dot area, but much lower numbers than your densitometer shows due to optical dot gain, etc.

SLUR FACTOR is a measure of the directional distortion of the dot typically caused by web speed or web tension issues. If you give a pressman a plate with round dots and he prints oblong dots, SLUR FACTOR will measure the amount of elongation or slur. I have print samples with nearly 175% SLUR FACTOR in the yellow, causing the midtones to be very warm. The pressman attempted to defend his printing by showing me the solid density of the yellow was 1.00, exactly where it should be. The rest of the story “is left up to the student…”

A fully functional demo version of the Betaflex PRO software is available at no charge. It comes with dozens of sample images of digital masks, films, plates, prints, etc. and allows you to actually measure all of the parameters described here.

Best regards,

Larry Goldberg
Technical Director
Beta Industries
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Re: Edge factor, Dot void factor, Slur factor

Postby Frank Burgos » Tue Nov 05, 2013 2:41 pm

Thanks, Larry!
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Re: Edge factor, Dot void factor, Slur factor

Postby grarom-va » Wed Nov 06, 2013 4:09 am

Now it is clear as the blue sky.

Thank you very much, Larry!
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