Presicion of register (printing)

I print with a Heidelberg Windmill and I have some really annoying issue with the “precision of register” (?). Apparently my machine doesn’t always print at the exact same spot, this is when printing or when die cutting. I have a suspicion that this problem is related to the thickness of the paper. Today I printed and made die-cuts of coaster-cardboard. The irregularities in register are 1-2mm….. Did anyone have the same problem and what was the solution? I know a Heidelberg Windmill should print super exact, so to be able to print flawless double-impression. Or do you have any hints what may be the cause of the problem? Thanks a lot.

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first question would be if you are doing it with or without guides if not your paper stock needs to be cut perfectly square and even all the way.
you can check your gripper margin by feeding one sheet drawing a line against the gripper and then pass the same marked sheet thru the other gripper and it should be the same helps sometimes to tape paper masking tape at the grippers.

If you’re not using guides, there’s always a little bit of variation. I almost never print without guides.

use guides, run slow if need be and best of all use the flying Dutchman technique. should be on the web under no more misfeeds.

Hello everone
Thanks for the comments. I print with guides and that’s when it happens.
Thank you Mike, I googled and will read this article carefully:

Thanks again.

try cleaning and deglazing the rollers

I found that the gripper guide will sometimes push the sheet too far if it is not set at full depth. It will go just under the sheet and shoot it to the left just a bit. There is a straight machine screw with a knurled adjuster on the right side of the platen for micro adjusting. Also the bottom guides slide on two screws and they can loosen or just get dirty.

It might be helpful to examine how much packing is used, how far the gripper is from the tympan, which direction(s) the error is happening, where the left feed standard is located.

Thick stock can lever itself away from the guides when the gripper opens at the side of the platen, when packing is thick.

Stock can bounce on the guides when it is dropped by the grippers, if it is held too high in the gripper.

Speed can often cause sheet bounce. Going slowly can help.

Stock can slide back in the guides, Peter L. would sometimes suggest a bit of double stick tape in the gauge channel.