Windmill grippers

Were having troubles with our windmill grippers. They are randomly only picking up our crane lettra by the inner corner rather then the full length of the edge of paper. Once the paper gets down to the platen, it slips out one end of the gripper and hence makes a mess all over our tympan.

Any suggestions on what we can do to ensure that our grippers pick up our 300gsm perfectly each and every time?


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Randomly you say.
My first question: Is it a long sheet?
300gsm is quite a thick sheet, is it catching something as it swings?
Have you established whether it occurs with both grippers?
Have you tested by gently pulling each side of the sheet when the gripper has closed on it?
If it slips out easily then I think you may need to pack the gripper with a little narrow thin adhesive tape.
Have your grippers got the narrow rubber strip inside?

Some thoughts—

Is the paper level across the gripper edge in the feeder? Sometimes stock will be inclined one way or another so that one side is closer to the gripper than the other. A piece of reglet or a wedge can be placed under the low side. Sometimes it helps to run smaller lifts, as the difference in sides is not magnified so much.

A number of adjustments may help. You can try more blast by screwing in the knob on the pump in back, or by shutting the delivery blast petcock; the height of the blast can be changed by the knob at the right-hand base of the front feed standard.

Lowering the suction bar to the “thicker”position will increase suction, as will the use of the larger-hole slide on the sucker bar. Or try rubber suction disks on the sucker bar.

Lengthen (or shorten—I don’t remember which) the 16- or 20-inch rod that connects the pile-height lever at the top of the feeder to the bottom pile-height gear. Try a half-turn out on the screw eyelet. Move the adjustable arc to “cardboard” at the bottom of the pile-height. Put a heavy rubber band on the pile-height gear’s pawl to prevent it from riding out of the gear due to wear or oil.

Screw in the 3- or 4-inch rod sticking out below the feed trip to the point at which the press stops when it fails to pick up a sheet.


Hi Brian,

“Lowering the suction bar to the “thicker”position will increase suction, as will the use of the larger-hole slide on the sucker bar. Or try rubber suction disks on the sucker bar.”

Not so; It doesn’t lower the sucker bar it merely changes the angle of the suckers to the sheet.

For 300gsm stock there should be no sucker bar slide used, and rubber suckers should not be necessary on a well maintained machine.

In my early days of platen operation sucker bar slides had not been invented and suckers were always used without any attachnents. Skill & experience were the order of the day, to obtain a profitable output around 3600 iph.

There is a vast difference between doing something as a hobby and doing it to earn a living.

Thanks, Bern—

Make that “Lowering the suction bar pointer…”.

One reason I like to use the slide in our shop is that some of our work comes off digital presses or copiers and has been passed over a heating element that makes it wavy. The slide seems to help flatten out the gripper edge.


Me again—

Make sure the little spring clip on the sucker bar is completely blocking the vent.


Thankyou all for your suggestions! We are off today to test the options :)

Hope too much info is a good thing. Here goes:
Sight down the sucker bar when it is parallel with the gripper bar and the gripper bar is closed. See if all of the sucker openings line up with the gripper EXACTLY. If not, either the sucker bar is bent or the gripper bar is bent.
See if one of the bars is more wonky than the other. If one bar picks up better, then the bad bar needs to be straightened. Use a 2pt lead under each bar between the bar and a bare platen (no Jacket or tympan). There should be even clearance from end to end and both bars should match.
Put a test sheet in each bar an pull to check tension. If the tension is light but even, you can adjust the little clevis (eye bolt) that is attached to each gripper bar. When the gripper is fully closed, the little cam followers that open and close the gripper bars must not be in contact with the cam. I try to set about a 1/64th gap. This is adjusted by removing the 10mm lock nut on the linkage stud that passes through the eye bolt. Unscrew the stud and remove. (Don’t lose it, they tend to walk off when you aren’t looking.) Loosen the 10mm lock nut on the eye bolt. Screw the eye bolt in to widen the gap, out to close the gap. You have to do this trial and error by replacing the pin (If it didn’t wander off) after each adjustment
If you get this set and the grippers still are loose, put several 1/2” strips manually in each gripper and test for even drag from the tip to the inside. If the drag is uneven, you may have to replace the bar.
One other thing that many of my customers find is that the sucker bar casting that is attached to the long rod that elevates the sucker bar has loosened at the connection. There is just a taper pin holding the two pieces and over the years, wrecks can loosen the connection. There should be almost no twisting motion in the sucker bar. If there is, the connection needs to be repaired.
While I’m overloading, take the jacket off and see if the gripper bar lines up with the right side of the platen when it is in the locked position, just before the platen closes. You should be able to get a 1pt. lead between the gripper bar and the bare edge of the platen. If not, then the gripper bar holder needs to be relocated. Not a fun job. Also check that the gripper bars do not contact the chase when the press is on impression. If you can see them deflect when the platen closes on impression, get them fixed.
If you need further info, feel free to email me.

Hi all,

I have a question regarding the grippers of the windmill as well. Just today I tried to print on very heavy stock (ca. 1.4mm) and everything worked nicely — the only problem is, that the grippers bite into the board quite a bit, I would cut these marks of after printing but I am concernet about the grippers — do they wear out doing this? Is there a way to adjust them for very heavy/hard stock? I couldn’t find anything in the manuals about this problem.

I am looking forward to any suggestions —


According to the manual the maximum thickness of the packing including the sheet to be printed is 1/25th inch, or approx 1mm. So you were well over the machine specs.

Heavy stock on heidelberg platen can be done without marking requires that you need a spare set and have a machine shop alter them (not in any manual) for heavy stock only. I had a similar situation did not want to alter my grippers so I ran the stock on my 12x18 C&P. We were imprinting information on the back of art board samples some of which were 0.120” thick very fussy work but the Chandler did the job 150,000 impressions and 107 type changes with linotype. In general the Heidelberg platen or cylinders will do more than the books say but at your own risk.

Hi, polychroma—

We very frequently run thick stock on our Heidelberg platens, including heavily laminated printing, chipboard, CD sleeves, thick adhesive-backed plastic. Probably most of this stuff is .050 - .070”. We run five small and one large Heidelberg. I can’t say that I’ve noticed any ill effects from running stock like this. The presses are probably fifty years old or more; if they are not quite mechanically perfect, well, neither am I at this stage. And I’m reluctant to ascribe any particular press problems to running this class of stock.

One source of gripper marks comes from over-packing the press, so that the stock is bent over the gripper edge of the platen. If you’re running thick stock, use the thinnest packing you can. I’ve printed .038” board using only a tympan and a draw (if needed)—about.009”. I usually take out any packing behind our .030” die-cutting jackets.

It seems to me that a more likely problem with heavy stock is the gripper failing to hold it. Booklets, for instance, tend to rotate out of the gripper since the sweep of the arm “throws” the stock a bit. I guess I’d run the job if it runs and not worry too much about it. If the gripper marks are an aesthetic problem, then your idea of cutting them off the oversized sheet afterwards seems right to me.


Hi Brian!
Thanks for your answers.
I have another question regarding printing thick stock on a windmill: Today I tested printing thicker, laminated stock, 2x300g and 3x300g papers — the grippers and paper transport in general are working fine, but I have another problem:
The paper hits the corner/edge of the platen when the gripper swing over the platen (I only had a tympan without any packing on it) and rubs over it. The platen corner leaves marks on the paper which are very light but multiply when printing more colors.

Do you have an idea how to get around this problem? Do you have experience with silicone spray or teflon spray?
I would appreciate any suggestions.


On our windmill we had a form fall out and one of the arms was bent ever so slightly. It took some doing to find out what and why the gripper was rubbing but the bottom line was that arm was bent lower than the other one. It also effected my registration. In the process on looking at each arm I also found that the grip on the paper on each are was not the same. One end of the gripper arm would hold and the other end of the same gripper slipped. What I found was alot of dirt, dryed ink and who knows what on the inside surfaces of both arms. After some cleaning of the gripper bar in question and reajusting for even gripping end to end both gripper arms worked like new and I never dropped another 16# sheet again. To be sure, I cleaned and adjusted both arms.

Hope this helps

Dana Warth