KORD 64 color shift

We have been recently experiencing a problem with 4 color screen tints varying in tone from lead to trailing edge of the sheet. We are running 150 line screen on 80lb. gloss book. I just had the operator change the ink forms with no luck. The new rollers had a durometer reading of 29 the old ones read 35 to 39. Still no luck. We will next try to reduce the vibrator roller oscillation. Any other suggestions?

 

Check for doubling. Use a 25x magnifying glass

 

KORD Color SHift

Aloha Mechanic,

I used a 30X viewer and did not see any visible doubling. We have a Dottie that can measure dot on the plate but unfortunately, our densitometer is not working so we cannot measure the dot on paper. We reduced the amount of oscillation in the vibrator rollers but that has not seemed to affect the color shift.

 

I have a couple of questions:

1) Screen is varying in tone on the same sheet in different positions , or on different sheets ?
2)If you print a full solid, what is the outcome?
3)I assumed that you still develope conventional plates the traditional way. Do you, or do you have a Ctp?

 

Is it possible to change the timming of lateral ink distibution on this machine? If u can maybe have a play around with that to see if u can get a smoother result.

 

Aloha Mechanic & Gazman,

Thank you very much for your input. As it happened, the solution was staring me in the face. There was no rosette pattern in the four color screen. Apparently, the tech who worked on a RIP problem on our platesetter set up a queue on our RIP to work around an output issue we had. This "mono" queue did not vary the screen angles but instead output all the screens at 45degrees. No one seems to know why there was no moire pattern which would have been a dead give away. It does however explain why the color shift was more apparent once the black was printed. The platesetter tech was forced to fix the initial issue of dropped elements and now we are out putting plates in the normal CMYK queue. Problem solved.