what causes gripper to tail end color difference

[viclpp]

I have a jobs that is the same color (green) ran 4 color process.

from the middle of the sheet to the tail end of the sheet it is a different color.


Is this caused from ink form to oscillator roller to heavy?

 

[Kaoticor]

We have the same issues on a particular job we run once a year. It is very hard to hold good consistency with so much color. If your roller settings are off, it could cause a lot of different problems, so I would make sure your roller settings are good first; form to oscillator is a quick check. However, do you know which color is creating the variance, since you are printing it with 4 color process? Is it all of the colors? If it is just one unit you might look at:

(1) Increase your ink fountain speed (while lowering keys)

(2) Your form rollers could be set too tight, causing a "bounce" when the plate cylinder comes around.

 

[dabob]

what kind of press and what model. . . .

 

[viclpp]

We have a shinohara 79

 

[RickLee]

There can be several reasons. but we would have to examine the whole aspect of the job. stock, grain, rollers settings, etc.

if the problem is only on this job then check the fit (register) of the job. it is possible that the paper is fanning out on the tail end of the sheet causing a flash of yellow to shift out. It would be hard to see without a good glass/loop.

I do not know the specifics of the press but can you change the initial discharge of the rollers on the plate. On the Heidelberg press it is possible to move that initial discharge forward or backward to help inn these situations.