Heidelberg cylinder feeding - Lettra

Anyone have any secrets on getting Lettra to run reliably on a Heidelberg Cylinder? I’m running 13x17” sheets on our KS and it’s very hard to get it in the sweet spot between picking up doubles and nothing. It seems like the texture of the paper helps pull the next one along with it. In this sheet size it seems too floppy for its weight, or something. I’ve never had trouble feeding smoother papers. I’ve got the blast all the way up, and have tried pretty much every combination of pile height, blast height, blast amount, sucker bar tilt, front separator springs, side separator springs, you name it. I’ve tried rubber suckers before and they simply pull more doubles, even when opening suckers off of the sheet. I’ve tried counterbending the stock to eliminate a slight upward curl. I’ve tried taping thin furniture onto the feed board a bit back from the sucker bar line to make the front edge of the paper flatter with intermittent success.
The vexing thing is I had a full pile run through without one stop or double this morning, and then awful trouble after that. I already thought of climate but it didn’t change much throughout the day. The form doesn’t have any large solids, just spare line art. I run tons of this paper every day on the windmill flawlessly and am very familiar with it on that machine, so this is driving me nuts (in case you couldn’t tell.)
Thanks experts!

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Had same problem a few years ago. Solved by detailed cleaning of air system.

Is the press equipped with an anti-static device? Or, have you employed such?

I would say that the paper pile is too close to the suckers, too high. You could try keeping the pile as low as possible with the air blowers separating (blowing) only few sheets at the top. You can get more air adjusting the compressor valve.
As for double sheet feeding, the transport area has a part which can be adjusted to the thickness of a sheet only. When the press picks 2 sheets, the sheets don’t go down to the gripper bar and the machine stops. Good luck.

Hello, Add more air, go to the gear side and find the hose that feeds the lead edge air blast, splice in a T- connection and add a small compressor, works good on these old machines…john

Heidelberg Repair.com

try opening the collar on the sucker bar to allow air in, or simply turn a few suckers off!

something you might try… you will need to jog the stock very precisely then, add a vertical strip of masking tape to the back of the pile. maybe two, three, whatever. the idea is to press the tape so it is in contact with each sheet. i have different tapes for diff purposes with diff levels of adhesive. some work better than others, some not at all, on a given job. the idea, when it works is, the feed arm in contact with the sheet it is picking, over powers the tape. the second sheet, with less vaccum gets held back.

Used your masking tape idea with bond on Heidelberg KSBA. Worked great. Thanks for the post.