We had a problem with registration movement while running to guides. We are running a 18pt 4 x 6 card with an uncoated front and UV coated back. The UV side is down. We noticed one of our grippers was not registering the same as the other. This never happens with regular paper. We are wondering is it the cam opening adjustment. While I have used it to set a controlled pick up I never thought about it being the release point for the stock to drop into the guides for register. We think the UV coating is fighting and not sliding like it should ( opening to small??) and maybe the stock is dragging a little and and then regrips in a different stop. Any ideas would be a big help.

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Flip the stock over and see if it makes a difference.
Try some anti-static spray.

We cant flip the paper over, the under side is UV coated and we are printing on the uncoated side. We found it was only 1 gripper bar doing this the other open was perfect. It was only 1/2 off which was the puzzle. I thought running to guides would correct this but is was causing it. I adjusted the cam opening so the both were the same but that really did not change anything. I felt the gripper is running to close to platen which may be affecting the drop away clearance as the open gripper opens to allow the sheet to drop and push to register. The gripper may still be pinching or rubbing along the stock along the edge in effect not allowing a free drop and push to register. This would explain the slight cocked crooked on every other sheet. I had an issue like this once before ( gripper underside to close to platen) when I doing some embossing and the underside of the bar was rubbing my counter at that time. I decide to try what I did then and it seems to work. That time I taped a piece of chipboard onto the platen to act like a guide to raise the running underside distance of the bar. I want to see if I can correct this the proper way.

What is the process of raising the tip of the grippers. Is there a way to control the overall height of the gripper as it passes over the platen I know I have seen mention of bending but is there a different way.

Western411, I had a problem with my windmill when I purchased it about 5 years ago. One gripper was out of alignment at the tip and would tear the tympan sheet. My fix was to ease off the bolts for that gripper and insert a brass shim to level off the gripper when the bolts were retightened. It worked for me and when using lays the registration is spot on

Thanks all for the feed back. The gripper show underside wear in the center. They most likely never ran much to guide I guess. I noticed when I bought it it would not register to guides worth a darn. I notice later one of the guides was upside down I got it to work like it should. I wonder if my grippers are bowed in the center over time due to a lot of die cutting and little use if the rest of the gripper face. I will keeping looking for answers.

I did try putting a shim in and in the process notice something else. Since the rubber is worn off my grippers I have added tape. I think I taped a little past where the old rubber stopped. I think this may be causing the gripper closure to be sort of altered and plan to re do both grippers over the weekend.

We found the issue. We thought our lay bar was bent so we have worked around that for some time. Sometimes it work sometimes not so good. The problem came back yesterday. I took both lay guides off and moved them to the far side sided by side. When laying a sheet into the guides I noticed it could not lay flat. One of my lay guides was dinged and a little twisted out of form. This gave one of the guides a high spot. I had an extra front lay guide so Iran the job using 2 front lay guides and the problem went away. all this time my issue was a untrue lay guide.