C&P Roller/inking problem

Hi all,
I hope someone can help with a roller/inking problem I am having with my 12x18 C&P. It seems, especially with some of the larger image areas on press that I am picking up some lines/ distinct pattern upon impression. It’s not a random mottling like I sometimes get on my Windmill, but have been able to fix. It almost looks like its the texture or pattern of the rubber roller material itself. I have tried raising & lowering the rollers with tape on the rails, adding more ink, less ink and more and less packing… When I start with little ink and think my roller height is about perfect on the gauge then add packing to start getting an impression, just when there is enough ink and impression, I get this pattern on the image that looks like lines.
I’m using regular masking tape on the rails wondering if that could be the issue? I’ll post a pic of what it looks like tomorrow morning when I get back on press to see if anyone can help. Of course the project is due tomorrow!!
Thanks for your input,

Log in to reply   8 replies so far

If you have over or under inking on the Form it’s an issue of the Form roller setting (height).

If eg you print a solid and you have Lines in the solid, this is a transfer from either the ink disk if the Form rollers don’t roll out the ink proper on the ink disk or the Form rollers skipping on the rails, than either the Roller Trucks don’t run right, may have a flat spot etc. Turn the press by hand on impression and observe the Form rollers.

How old are your rollers, new rollers make a big difference.

Sounds like the rollers could be bouncing on the rails and not picking up ink smoothly. How is your ink tack. Not to thick ? You could soften the ink a little, but be careful of set of. Is the pattern exactly the same on each impression ? How did you resolve the prblem on your windmill ? good luck !

Without a picture it is a little hard to diagnose. You don’t say if it is a large solid, just a large image. If it is a small enough pattern to replicate the grain of the rollers than it might actually be the paper.
Try turning the sheet 90 degrees, see if the pattern goes with it. Also try turning the sheet over, as papers are all very two sided. If the pattern stays the same it’s in the ink train. If it moves with the paper, its the paper.

Thanks for the responses and suggestions.
My trucks and rollers are almost new and don’t seem to be skipping or sliding on the tracks which have masking tape on them. I ordered the hi density tape from NA Graphics and will put that on to see if it helps. Otherwise, I am still at a loss. Here are a couple of pics of what the lines look like.
Thanks for the help,

image: Lines1.jpg


image: Lines1.jpg


Looks like a laid paper to me. Take a blank sheet and old it up to the light to see if you see a similar pattern. If so, the pattern is from the mold with which the paper is made. It leaves tiny areas where the paper is thicker and thinner in parallel lines. More impression may help. Though I haven’t tried it, dampening may also help. I just avoid laid paper.

You don’t say if you are printing from photo polymer or not. I suspect you might be. I suggest you try a different adhesive that come in flat sheets, not rolls. We have used adhesive from rolls with a krinkled protective layer and my suspicion is the krinkle leave a pattern on the adhesive that translates to the plate and printed surface on solids. Just a thought.

It appears the pattern is not in the red area. Why not? What was different?
Did you try rotating the sheet 90 & 1800 degrees to see if the patter follows the paper. Then rotate the plate and see if the pattern also rotates. This will tell you if it is in the paper or the plate, or the roller train, if it remains when you rotate the other two parts it’s probably the rollers.
This dose not necessarily mean you have to run the job in a different position but by scientific method you should be able to isolate the problem.
I like the adhesive liner thought mentioned above. Something else to check.