Dot gain in shadows (flexo)

Polyprintgirl

Active member
Any ideas on how to keep the shadows open outside of a press compensation curve? We're having trouble keeping our shadows open, they seem dull and muddy.

We are currently applying a press curve; we output round dots; 150 line screens. Our screen angles are 7.5 YEL, 22.5 CY, 52.5 MAG and 82.5 K. Our press is water based. It was suggested to use an elliptical dot for process work, rather than round, because it makes a better rosette.

Our first option will to output at 150L with elliptical dot
Depending on the elliptical dot output, our second option may be to output at 150L round dot with a more open press curve (to open up 3/4 tones-shadows)

Any thoughts or comments on this would be greatly appreciated.

Thanks.
 

gordo

Well-known member
Any ideas on how to keep the shadows open outside of a press compensation curve? We're having trouble keeping our shadows open, they seem dull and muddy.

We are currently applying a press curve; we output round dots; 150 line screens. [snip] Our press is water based. It was suggested to use an elliptical dot for process work, rather than round, because it makes a better rosette.

Our first option will to output at 150L with elliptical dot
Depending on the elliptical dot output, our second option may be to output at 150L round dot with a more open press curve (to open up 3/4 tones-shadows)

Do not use elliptical dots - they do not have anything do with creating a "better rosette" nor opening up the shadows. Round dots are the industry specification for flexo. If you cannot solve the problem with a plate curve or adjustment in the images you are sending to your RIP then you may need to consider an "XM" or hybrid type AM screen that lets you specifiy the minimum sized dot that will be used. I.e. use a larger shadow dots to achieve the same final tone in your presswork.

best, gordo
 

meddington

Well-known member
Seems easier to address through curves. What's the Image total area coverage (max shadow value)? Lowering linescreen to 133 might help.
 
D

Deleted member 16349

Guest
Any ideas on how to keep the shadows open outside of a press compensation curve? We're having trouble keeping our shadows open, they seem dull and muddy.

We are currently applying a press curve; we output round dots; 150 line screens. Our screen angles are 7.5 YEL, 22.5 CY, 52.5 MAG and 82.5 K. Our press is water based. It was suggested to use an elliptical dot for process work, rather than round, because it makes a better rosette.

Our first option will to output at 150L with elliptical dot
Depending on the elliptical dot output, our second option may be to output at 150L round dot with a more open press curve (to open up 3/4 tones-shadows)

Any thoughts or comments on this would be greatly appreciated.

Thanks.

As I understand, flexo tends to require very light pressure (plate to substrate) for screens and higher pressure for solids to obtain a good print. Can be a problem when both are in the same image.

Maybe the crews are applying too much pressure for that screen condition. Or it could be that you are using a anilox roller screening value that is not suitable. Just a thought.
 

Polyprintgirl

Active member
Gordo, that's another one of the press foreman's comments, that our dots are "bigger" than the sample (we're trying to match). We haven't purchased any AM screens outside of these that came with Esko.

Meddington, I'm not sure what the max shadow area is, they've been experimenting today at our TX printing facility (I'm in Denver). Guess I could have them try to measure that with the spectro, eh? We started with 133L then went up to 150L output for our last stab. They want to try 185L but that will only muddy things up further, right? We're trying to match a solvent-based sample, also.

I'll change the output curve to try to compensate for less gain in the shadow areas. Attached is what we're using currently.

Thanks for your input, Gordo and Meddington!
 

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Polyprintgirl

Active member
Erik--we're in testing mode, so yes, there could be too much pressure. They're currently using 1000line/2.2 bcm aniloxes.
 

meddington

Well-known member
I'm not sure what the max shadow area is, they've been experimenting today at our TX printing facility (I'm in Denver). Guess I could have them try to measure that with the spectro, eh?


I was referring to the max CMYK value of your images. An ICC profile used for color separation would have a TAC defined upon its creation. Typically 320 (CMYK values at darkest add up to 320) for sheetfed offset, 280-300 for web offset, 260, maybe lower for Flexo. If your separations are separated for SWOP, your TAC may be too high.
 

Polyprintgirl

Active member
Well, heard about "Friendly Flexo"--turns out the image we're trying to match had been altered to make a "skeleton" black and adjusted for drop-off. That explains a lot. Guess I'll try to alter our image to try to get it to open up. Move the detail to the K plate, remove dot from the CMY plates, will take some R&D.

Thanks for input from all.
 

FlexoGrunt

Well-known member
Well, heard about "Friendly Flexo"--turns out the image we're trying to match had been altered to make a "skeleton" black and adjusted for drop-off. That explains a lot. Guess I'll try to alter our image to try to get it to open up. Move the detail to the K plate, remove dot from the CMY plates, will take some R&D.

Thanks for input from all.

We have to examine every sample we get very closely as it seems everyone has a "trick" that they do in flexo printing. Well, if you're trying to duplicate it that is.
 

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