Heidelberg CD102 6col - Grip Issue

[herbert]

Hi all

I work in PrePress and have 42mm Plate edge to Paper Edge, then 15mm grip. When the Job has been printed the grip has printed at 17mm....This has caused an issue when folding because we need 15mm at Grip and tail. We now have 17mm at grip edge and 13 mm at tail edge.

Can any on explain why this would happen and change on press ?

Thanks

Dan

 

[KeithManning]

Have your press operator check the position of the plate cylinders.
They may have been rolled and not put back.

This is assuming you've been using the same first-trim/gripper dimensions
with no issue on other jobs.

 

[CD102]

Front Lays?

Front Lays?

Also have the operator or mechanic check to make sure that the front lays on the infeed are set properly.

 

[printerpete]

Front lays set wrong for that job

 

[spider]

The front lay stops need to be reduced but you may get problems when printing solids

 

[Randy]

Possibilities: The head stops were maxxed out, plate cylinders not zeroed at the console, plate cylinders jumped.

2 mm is enough to mess up the folder, but easy to fix on the 102. I hope the pressman was given the info, and checked that it was centered before it was run.

 

[rbailleu]

if it happened on only one set of plates it was probably the press. if the paper was short by 1mm and the gripper/ plates moved 1mm then you could be easily off with out to much change. press person should have made sure that the job was centered. if everything is off then you need to change your plate template. but they should be able to fix the press sheets with cutting and folding it just may triple the work. if this was a big job they shoul have checked it before they okayed it to run.

 

[herbert]

Thanks for the info.....All jobs are out my 2mm, so I think its a press issue. In future we are also going to make sure the impo layout, which is supplied with each Job states the required grip. The Press guys are saying the cylinders have not be moved..they are now checking again....thanks

 

[rbailleu]

if all jobs are out 2 mm then let them run the press like they have it and change your plate templates its a 5 minute job in prepress one time. if they change there mind you will probably have to change again, but its still easier to change a plate template than every job on the press.

 

[herbert]

I agree with that comment, but we have 2 102's - one prints correct grip the other is out. We use the same output queue in prepress for both. Maybe i have to create another queue to reduce the 2mm for the problem press. Im a little concerned to to change things straight away.

 

[CD102]

But the question again is, has anyone checked to make sure the front lays are correctly set and that the plate cylinders are at their zero point? There is something different between the two presses. Fix the press that is wrong.

 

[CD102]

One more thing to point out, sometimes the servo motors stop working for the front lays. I know that on the older presses, if they couldn't establish their zero points that the numbers would flash on the monitor. We always had ours set on 11,00 but there were times they would move or get moved and then they didn't get back to where they belonged because of dirt gumming up the works.

The same was true of infeed gripper height. It was supposed to be twice the sheet thickness. One crew went from .030" stock to .016" stock and couldn't figure out why the press was dropping sheets. They had set the numbers correctly for presetting, but the servos for setting the gripper height were stuck nearly wide open. The press crew didn't realize what it meant when the numbers were flashing.

 

[rbailleu]

yes that is a good point i idid not realize that you had 2 of the same press. one has got to be off. either they moved the zylinders or the grippers. otherwise you would need 2 workflows which would cause more issue as they would then be locked in to each press once the plates were made.

 

[jbeniston]

One more thing to point out, sometimes the servo motors stop working for the front lays. I know that on the older presses, if they couldn't establish their zero points that the numbers would flash on the monitor. We always had ours set on 11,00 but there were times they would move or get moved and then they didn't get back to where they belonged because of dirt gumming up the works.

The same was true of infeed gripper height. It was supposed to be twice the sheet thickness. One crew went from .030" stock to .016" stock and couldn't figure out why the press was dropping sheets. They had set the numbers correctly for presetting, but the servos for setting the gripper height were stuck nearly wide open. The press crew didn't realize what it meant when the numbers were flashing.

Sounds to me like you need a service call from HD. Print some dry solids with the settings at specs and measure the print free margin. On most presses the gripper bite and the gripper margin are different.
If you can stop the machine where you can access the impression cylinders with a sheet in the grippers, cut the sheet along the edge of the gripper, two at each end will do. Measure the distance from the sheeet edge to the cut marks when you get the sheet out of the machine. I do not know a whole lot about Heidelburgs but I would think that this measurement should be equal to the standard gripper bite considering that the front lays are properly set. The HD guy will be able to match the electrical setting of the front lays to the mechanical position,ifyou have a problem.
Hope this helps a bit.