KBA marking problem

Having problem with C1S stock being marked on coated side. This problem is random and does not repeat sheet to sheet. 2 pictures show the marking on the coated side and the uncoated side of the sheet above. 2 different papers are being used, problem only affects 1 of them. Paper affected is .012 C1S from Tembeck, paper not affected is Tango .012 C1S. Any ideas?

 

Hi Chris,

What is the configuration of the press?

I have already encountered a similar problem on a KBA with several varnish groups, do you have a varnish group out of pressure as a result of your printing?
The cause may be a light deposit of ink in it.

Or a deposit of ink / varnish on one of the many leaf guides in the press, causing these traces.
[From Google Translator]

 

No varnish or other coating. Marking/offsetting only on gripper edge.

 

And, happening on 1 manufacturers stock only.

 

Setoff caused by sheet delivery.

 

Why not affecting both stocks and why random? Appreciate your input..

 

Different stocks deliver differently because they’re made differently...and setoff is almost always random. Hard to say without being there but probably the stock having issues has more of a down-curl to it, and if so, it might be causing the gripper edge side of the sheet to contact the sheet below it. There are other possibilities, as well.

 

Is the grain direction on both stocks being run the same?

 

If the transfer drums are in , take them out. you don't need them anyway

 

you're right, short grain could be a problem