Gray Balance consistency run

kewlbigdan

Active member
To resolve a print inconsistency we are encountering, we created a full AR/AC box of 50/40/40 and ran it on the narrow web press.
This test was to see if the color varied or if the press could hold a grey balance.
We ran the test and the results were brought back to Graphics for review. I can see gear marking, but also a hue change in the AR from a soft yellow to a soft magenta. This coincides with a print issue were are fighting. But the press now said this issue are normal and printing the GrayScale over the whole area was a near impossible feat.

Our press guys are really good, so kudos for them giving this a try. My thoughts are though, how hard is it to print such an 50/40/40 box consistently around the cylinder as apposed to a process image consistently around a cylinder. IF you can't print one, you can print the other.

Am I missing something?
IMG_20200421_113926.jpg
 
Last edited by a moderator:

curiosity

Well-known member
Perhaps one of the more difficult things to run, but certainly not impossible. Yet, don't expect perfection. It will reveal issues as you can already see. We've done similar and our pressmen got to work on reducing chatter as well as working with their ink phase charge. Your example seems to show a slight imbalance from lead to tail in your phase, but relative consistency from left to right.
 

gordo

Well-known member
To resolve a print inconsistency we are encountering, we created a full AR/AC box of 50/40/40 and ran it on the narrow web press.
This test was to see if the color varied or if the press could hold a grey balance.
We ran the test and the results were brought back to Graphics for review. I can see gear marking, but also a hue change in the AR from a soft yellow to a soft magenta. This coincides with a print issue were are fighting. But the press now said this issue are normal and printing the GrayScale over the whole area was a near impossible feat.

Our press guys are really good, so kudos for them giving this a try. My thoughts are though, how hard is it to print such an 50/40/40 box consistently around the cylinder as apposed to a process image consistently around a cylinder. IF you can't print one, you can print the other.

Am I missing something?

Hah! The can of worms has been opened!
The grey balance patches in the color bar (or spread across the entire sheet) on live production runs has very little to do with the color balance of process images in the live image area.
You can read more detail about the how and why of the fallacy of using grey balance patches here: Grey Balance Unbalanced – An inconvenient truth
Your press should be able to print SIDs across and around the cylinder +/- 0.10 density from your standard SID aimpoints.
There are very many causes if your press cannot print SIDs within tolerances.
 

SteveSuffRIT

Well-known member
Can you supply a photo without a glare from a camera flash?
In real production, you would never print CMY gray balance, you would use a high amount of GCR.
CMY gray balance is good for press diagnostic because its very sensitive.
Steve Suffoletto
 

Alois Senefelder

Well-known member
kewlbigdan,


Terminology! AR = Around ? AC = A cross ?

So you mean a FULL OUT Solid/Screened Halftone ????????

1) Are you using "Photopolymer Plates ? 2) Are the Plates being mounted correctly ??

3 Is the Anilox Roller OK ?


Regards, Alois
 

Slammer

Well-known member
What ratio pixel size to anilox cell are you on?
I have seen similar effects with a low (1:3 to 1:4 ) ratio
 

kewlbigdan

Active member
Thank you all for your responses to my posting, given that I didn't add all the data needed for everyone.
The photo without the glare was near impossible and I didn't take time to find a way to do it properly.
Possibly I named this incorrectly as it was not a gray balance test as such, but a way to see if the press held the same color balance everywhere or we had hue shifts. I didn't really care about the final color as long as it was consistent.
Gordo is correct, this post was in concert with a number of other posts related to the issues we were seeing on the press concerning dot patterns between stepped images and the resulting hue shifts between these stepped images.
This test was to see if the press has printing consistent.
It was determined today, we had installed LED lighting about the press and not shielded the lights. This could be drying out the ink or hardening the plates when the press is idle.
It was also found the mounters were reusing stickleback and overlapping it as well. Lets not go there. I have no words.
 

curiosity

Well-known member
Be wary of those that do not seek to understand a problem, but instead deflect blame to others.
Then again, my experience is that "those" will always be that way, and you will have to just suck it up.
 

danremaley

Well-known member
To resolve a print inconsistency we are encountering, we created a full AR/AC box of 50/40/40 and ran it on the narrow web press.
This test was to see if the color varied or if the press could hold a grey balance.
We ran the test and the results were brought back to Graphics for review. I can see gear marking, but also a hue change in the AR from a soft yellow to a soft magenta. This coincides with a print issue were are fighting. But the press now said this issue are normal and printing the GrayScale over the whole area was a near impossible feat.

Our press guys are really good, so kudos for them giving this a try. My thoughts are though, how hard is it to print such an 50/40/40 box consistently around the cylinder as apposed to a process image consistently around a cylinder. IF you can't print one, you can print the other.

Am I missing something? View attachment 290001
Printing 50/49/40 is impossible! These values are at or near the midtone area - where the midtone dot gain changes under the best conditions (+/- 2%} is the standard deviation of a good press! So as long as these gains climb together- you get a ‘darker’ grey - when one goes up or down relative to the others a color shift results. Same problem with purples and browns! See my PC Reference piece to confirm! The secret is to use GCR to add black and reduce the near midtone values to 20/30% where the dot gain doesn’t shift!
Flexo, Web, Sheetfed - doesn’t matter.
Also- I hear a lot of “chatter” about ‘in-line’ color “changing color AROUND the cylinder.
When a press is set up correctly the ‘fall off’ of the solid front to back is .07 density - color won’t vary around cylinder in .07 change!
 

Canon Research

Canon
Advancing Productivity and Service Delivery
Enhancing the Print Customer Connection (Part 4)

Read All About It

   
Top