Heidelberg T registration issue

When each gripper picks up the sheet, stop the press and draw a line along the gripper edge on the paper. Compare both sheets to see if there’s some issue with how one gripper picks up the sheet compared to the other.

“Standard setup” is a bit vague. I’d ensure all the settings are correct for using guides.

Minor differences in grippers should not make a difference unless running commercial register (no guides).

As Anonymouse says, running in registration mode the initial position of the gripper bar does not make any difference because the bar releases the sheet at the bottom of the stroke to allow the side guide and lays to position the sheet accurately before closing again to deliver the sheet. Possible causes for mis-registration include but are not limited to static, being too far from the guides when picking up the sheet and also being to close to the guides when releasing so that the sheet bounces. There are two initial positions for the sheet guides, one each for the brass lays and the nickel guides. Make sure you are using the brass positioning guides at the lower left of the sheet stacker. Dusting the platen with a light coating of baby powder often allows the sheet to slide easily into position and static tinsel strung at the top of the feed table can also dissipate static.

I bet you didn’t change the screw on the gripper head that says “with guides” & “without guides”

My grippers are uneven just like that but if they’re truly dropping the sheet onto the guides then the misalignment isn’t an issue.

Make sure your packing isn’t preventing the sheet from dropping freely to the guides.

Be sure to report back when you solve the issue!

I go by the book so my settings are all set for using guides, screw is in “with guides” position, the guide knob is locked on, and the stack is positioned at the brass guides position. I am aware that the gripper releases the paper for positioning but i wasn’t sure if it applies to the side guide too. I’ll replace my packing once again, try out the line thing to be sure of the difference, and account for static of which i wasn’t aware as an issue.. I’ll be reporting back
Thanks everyone for the fast replies!

Flying Dutchman

Sorry lost the reference, non native speaker.. As in not a good sign?

Flying dutchman is a trick with the tympan, a google search should get it for you.

Ok, sounds like the setup is complete. However, it should be noted where the side guide is positioned. Ensure the guide and linkage are securely fastened and move freely.

Sometimes the guide will hit the back of the stock* as it extends. I’d cycle the press slowly by hand with the power off and watch closely each event: pickup, drop, guide extension, impression, grab and delivery. A helper to turn the press while you watch the right side is handy.

It can be helpful to put a piece of double stick tape, or otherwise rough-up the channel of the lower lays so the stock doesn’t slip when the lays push the stock to the right.

Since it happens alternately, gripper is suspect or at least related (my comments above notwithstanding). I’d try to identify if one in particular is the culprit. I’d mark each gripper (A, B) and perform the line test described above, and see if there is a correlation; that may indicate gripper misalignment or bend. I’d check for a bent gripper by opening and closing the gripper when the press is stopped just before the gripper opens at the delivery - there it can be manually opened by pressing on the linkage. If the gripper end moves when opening, it is bent. I’d check for ~1/8” clearance as the grippers sweep across the tympan (properly packed).

*(all, or one type in particular?)

Chime back and let us know your progress.

Regards,
AM

I rechecked my settings, replaced my packing, took off the side guide and cleaned some muck, and put some baby powder on the platen but the problem persists. The grippers pick up sheets with minimal differences so no problem there. After some observation i think that the problem might be the timing of the side guide, since some sheets even went over it not allowing it to move up and other sheets remained at about 1mm from the guide at printing position.. Do you think this is a possibility? maybe a worn out part?

Mike is referring to this technique wherein one cuts a little flap in the topcoat of the packing, in a particular way so as to cause it to protrude slightly and ‘catch’ the edge of the sheet as it is delivered- causing the sheets to lay in the same spot each time and not ‘bounce’.

Google “Flying dutchmen” technique or search on briar press for it, it’s mentioned a few times in posts previously.

Ensure the big silver shouldered pivot bolt holding the sidelay lever is not loose, I’ve seen it cause this. Also ensure the lay spindle that runs laterally through the platen moves freely (unlock the knurled knob and manipulate the linkage) and check for any binding and/or loose wiggly bits.

Lay timing can be adjusted, but it is critical to rule out other factors first, like if the gripper timing is off… a collision with the sidelay could result.

You might try using the “cheaters”, the thin rods that hook onto the front feed standard to reduce the distance that the grippers grab the stock ~6pts.

Sorry for the absence, i really had to find a way to finish this job.

First of all, AnonyMouse we posted at the same time and i hadn’t seen your post. Shortly after posting i pretty found my problem since one of the grippers stopped picking up sheets properly. It either trashed them at picking up or flung them around the room, so i’m definitely looking at a bad gripper. To finish the job I used a flying dutchman (handy little trick!), roughened up the lays and i printed on every second, which needed a lot of coordination but it worked out okay since i was printing halftone and the double inking gave good results.

The silver bolt and linkage on the side lay is good, since i dismantled it, cleaned it and put it back together, with no difference in results.

Now that i’m a bit calmer though i’ll take it from the top again, considering all your very valuable input, and check if the “good” gripper gives perfectly consistent register.

Thanks a mill everyone for all the help, this place is awesome! I’ll be back with more definitive results.
Jim