Flexo printing – Unstable gradient in GMG Opencolor after measuring test charts

Match

New member
Hello, I'm Mat. I'm new here and writing because I couldn't find answer for my problems anywhere in the Internet. I'm hoping that here is someone who can help me a little with profiling.

We're printing from flexo plates on foils / flexible packaging.
The printer I use is EPSON SP C7000.
I use:
GMG Opencolor for profiling
ColorAnt to averege measurement
GMG Colorproof for printing

My problem appeared when I tried to make a profile for 120l/in print. At first it seemed like everythings allright – test images look nice and comparing to foil print, the proof is satisfying. But the gradient circles and stripes aren't.

In the photo I attach you can see that there are repeating loses of dot gain. It starts from the smallest dots and seems to fade at about 16-18%.
I couldn't make a good photo of separated colors (CMYK) with my phone but it's similar for all colors.
The photo shows the circle with whole CMYK (0-10%).
What is strange that the loses of gain appear after every 3% and persist for about 1%.

It's 2nd profile for this lineature, because the first one (on another substrate) was a lot better. I didn't see that problem then, but it exist there too.
Profiles with exactly the same testcharts and photos but in 150l/in are pretty good.
I don't know where is the problem: the test prints of plates, the GMG software, ColorAnt or EPSON printer.

Have anyone seen such problem? Can you give me some advice how to deal with it or where to find the source of this problem? Thank you in advance.
 

Attachments

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SteveSuffRIT

Well-known member
The photo you show is of the proof, not press printing?
Most proofs are inkjet and continuous tone (con-ton, CT), so why do I see a rosette dot pattern?
Are you proofing with a dot? (Why? What happens if you don't?)
 

Match

New member
We print dot-proofs for clients that simulates how it will really look like after press print.
I didn't try con-tone, because dot proof is what I'm interested to achieve.
However it's interesting point and I'll try to print con-tone proof to see what result it will bring.
 

EricJ

New member
Hi Mat,
Have you tried reaching out to your local GMG support office for assistance or the help center on gmg’s website?
 

Match

New member
I did contact with GMG support and we're trying to solve this problem.
I have also tried printing continuous proof and it seems to be ok.
Next thing is that I start to connect some of issues with proofing:

I'm trying to create profiles for lineatures 48 and 60 l/cm (about 120 and 150 lpi).
48 (120) – I get some problems with regularity of gradient
60 (150) – The moire effect is showing up but noticeable only in K and V (I've made CMYKOGV tests, but OGV testchart is measured separately)

I tried to print the black gradient with older profiles that are being used all the time. The problem stays even if I use older ones.
What is curious that there's better effect with 52 l/cm (around 133lpi), but still it's not smooth.

The problem is most visible at around 8-12% K in line gradient. At first I didn't notice it and now I'm considering that it might be a problem with Epson printer or somewhere else than with GMG.
What do you think about it?

The photos I've added are on grayscale, because it is more noticeable that way comparing to what I see.
 

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