Heidelberg Windmill gripper making marks

Does anyone have a thought as to why my Windmill grippers would mark the paper? It is about 1/4 inch deep down most of the length of the card (about 5 inches down, top to bottom). I’ve been cutting and scoring on it all morning with no issue. The problem arose when I switched to just scoring. The paper I’m scoring is a 6x9 130lb cover that has a deeply impressed image on one side (which is causing the paper to warp slightly). Most of my cards have images with deep impressions but this is the first time I’ve had an issue with the gripper. Not sure if that is the problem or if it is something else. Any thoughts? Thanks!

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On occasion I have moved some lead strip spacing material that was at the gripper end of the chase out for a position adjustment, and in the process of pulling out the strip of lead and moving it I left a 2pt or 6pt that was next to the removed strip up just enough that it would leave a mark on the sheet but not enough to smash the lead down to show what I had done.

Just a thought.

I’d bet it has nothing to do with the fact that you’re scoring. Especially since it’s 1/4” into the sheet, the grippers shouldn’t even grab that much of the paper.

Most likely something in the chase is pushing on the paper when it’s on impression. Does it leave a mark when it’s off impression and you run a sheet though? Also check the inside of the grippers to make sure there’s nothing extra in there just in case

One tiny test possibly, if the grippers are parked at 3 o,clock and 9 o,clock, in turn, (MOTOR OFF of course) one at a time the grippers can be opened by depressing the tiny adjustment links, with the Heel of the palm of the hand, open the gripper, so, grip a sheet of stock in use, release in the same manner, X 2, to prove or disprove where the problem occurs.!
In the first line of your post, you use Grippers plural, in the last line but one, you use Gripper singular.
My efforts are probably rubbish, but perhaps if you clarify either one or both effected may give the Experts a better chance.

Are you still within the Minimum permitted grip allowance, as implied by the first response above.

As you state just switched to scoring only, is the scoring rule close to the grip, and the stock merely deforming over the recess in the chase, at the grip edge, again probably rubbish but as before, see above.. .

Thanks so much for your replies. I have confirmed that the mark happens on each sheet of paper, therefore both grippers are the problem. I was incorrect about the size of the mark, it is closer to an 1/8th inch. It occurs once the paper is first taken by the gripper before it is dropped on the guide bar for impression. I believe that the gripper bite is too much. It’s a strange problem to happen all of a sudden but I have ceased to be surprised by these machines. Does anyone know how to loosen the gripper bite? I cannot find this info in the manual.

I’m not sure if there is an adjustment for loosening the grippers but I’ve taped layers of chipboard inside the grippers (where the stock is not) so the gripper doesn’t bite down so hard on the paper.