Flexo repeatability issue

[kewlbigdan]

Not sure this is the correct forum. We are having issues with repeatability on a Flexo press with a Shrink material.
The issue is repeatability of the SID targets from one run to the next. Wondering if anyone has any insights.

We print highly decorative cosmetic shrink labels.
We have Esko based workflows, HD Flexo crystal screening, with microcell Pixel+.
Esko CDI and XPS systems.
Plate material is .045 Dupont EFX flat top plate material with associated FAST thermal processor.
Press is a MarkAndy P9 with LED curing, Siegworks Gracol13 UV Inks, 1000c 2.0 bcm Anilox rolls.
Print substrate is a Shrink material that is printed subsurface, KCMY rotation.

We have had 2 G7 Color experts (The guys that were part of the creation of G7), Plate experts, Ink experts all onsite to find a solution. This has been plaguing us for 9 months.
Fingerprints performed and all targets fall in directly with minimum maneuvering. P2P and TC1617 are measured and are 93% match to Gracol13 (CRPC6) standards. Curves are built and when going back to Verification 2 - 5 days later, the press set-up exactly per the tech sheet from fingerprint, everything checked, We cannot get back to the same Lab or density values on the SID targets without major adjustments to anilox, impression and falling outside the CRCP6 standards for 100/100/100 overprint targets.
We have done this multiple times over the past 5 months with same results.
We have checked ad nauseam; Esko rips, CDI settings, Plate material, Inks.

Any insights or help would be greatly valued. thanks

 

[SteveSuffRIT]

When measuring SID, are those conditions the same?
Same backer material?
Is shrink film directional (angle) sensitive?
How far off are SID and dE from target? +/-0.07? dE < 2.5?
Is the 100/100/100 important?

 

[Cornishpastythighs]

Not sure if this is relevant Do you have a regular Anilox roller cleaning procedure in place and do you have a way to measure/check the condition of your Aniloxes

 

[SteveSuffRIT]

UV ink won't dry inside cells (and reduce volume and SID) like solvent or water-based inks.

 

[kewlbigdan]

Steve; The measuring conditions are exactly the same. using the same setup, inks, anilox etc, our SID dE can be greater than 4 or as high as 12. or very close. There is no predictability.
The 100/100/100 is not extremely important but definitely throws off the 50/75 patches. Unfortunately, we print in the 1-20% frequently, so any deviation is rejected.

 

[kewlbigdan]

Cornish: We have a "mike" meter (I am Graphics, not press, so I have no idea what that is) and am assured the Anilox are measured. As for cleaning, We have a cleaning machine, but not a ultrasonic type. Again unsure of maintenance schedule.
the Press has LED curing lights for the UV ink. We, non-press people, have speculated the LED lights could be curing the inks on the plate or in the anilox rolls. We are assured it is not. Could it?

 

[SteveSuffRIT]

"Mike" is probably slang for "Microscope" or "Micrometer" to measure cell volume (depth).
If LED lights are curing inks, cell volume would get lower and SID would get lower also.
Concern is SID repeatability over a few days?
What is SID repeatability over a shorter time frame, like a 8 hr shift? Is the same operator repeating the setup?
Can you tell us more about the shrink substrate with a printed subsurface?

 

[Cornishpastythighs]

Cornish: We have a "mike" meter (I am Graphics, not press, so I have no idea what that is) and am assured the Anilox are measured. As for cleaning, We have a cleaning machine, but not a ultrasonic type. Again unsure of maintenance schedule.
the Press has LED curing lights for the UV ink. We, non-press people, have speculated the LED lights could be curing the inks on the plate or in the anilox rolls. We are assured it is not. Could it?

when I was running UV litho we had to have all the lights around and over the press 'shielded' against the stray UV light from our plant lighting. It would start the Polymerization process of the ink in the ink fountain and rollers. Just some info from a UV litho guy.