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if you are using your gauges the gripper should open up and drop the sheet on the gauges then close up to remove the sheet after it is printed, sounds like you didn’t set the gripper to open. ps, we are all idiots, don’t feel bad.

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Dick g .
i wonder if you have under stood the terminology !!
we call the two upright stanchions in the feeder and delivery lay standards . when you feed thick stock it bashes against the left side stanchion . the best way around the stanchion knocking the sheet out of the gripper arm is to put something under the trailing edge of the stak to raise it a bit to reduce the odds of it knocking against the stanchion . however having said that i would check that the gripper is actually holding the sheet securely in both grippers and that the sheet is going into both grippers without catching the grippertop and that the gripper is closed at the point of suction release,and the suction release has allowed the sheet to move off in the gripper and released it in sufficient time not dragging the sheet out of a weak gripper.

Sorry but as i wrote it grew into an epistle !! The trouble with feeders is there are loads of things you wont realise have been adjusted by previous owners and many operators run very low piles to help overcome doubling this can be a cause to of stanchion contact . Take a look at the pile raising gear and you will see a crescent slot with a hinged block that has an arrow reading paper one way and card the other ,if i guess correctly you are printing on planks of board and that would require you alter the pointer toward card about three quarters of the way , then compensate with the normal control at the top and add tilt if possible as well as keeping the sheets aired up for the top three to five sheets rising as the blow puffs .

If you are printing on guides, you can afford a little slop on your feed table. I’ve over come the same issue by slightly twisting the stanchion. I’ve also raised the back of the pile with a reglet.
Bill

Waldwick it is i think the stanchion that is the problem , not register , the register problem is caused by the tail of the sheet hitting the left feeder board stanchion and knocking the sheet out of one side of the gripper so then its out of position when the sheet is dropped onto the headlays (and then probably too far from the side lay for the action of sideways jogging to bring the sheet to the side lay itself or even dropping it too close and its springing away from the lay .) however you are advising correctly how to overcome the problem that also can occur and your twisting of the stack via the feedboard is common practice to over come sheets not making the side lay and then not being picked out of the platen after impression has taken place .

I have a preference if printing on 350gsm + to place a wedge under the tail of the stack raising it over an inch sometimes stops the back left from hitting the stanchion so hard reducing the odds of it pulling the sheet out of squre in the gripper