Big problem with primaster 74-2 model 2007

Dear sirs,

I would like your assistance on a problem I have encountered regarding my printing machine Heidelberg Printmaster 74-2 model 2007.

For the last 4 months it is not possible to align the registration marks during the second pass of the sheets.
The case is the following:

I print first 2 colors (first pass) and when I print the second two colors (second pass) of the sheets, the registration marks have “expanded” 1-2mm.

Technicians have been called many times to fix this but they do not seem to find what causes this.

Please take into account the following:

1. The problem is with the alignment of the color registration marks between the first and the second pass.
2. This “expansion” is observed during the second pass, especially on the opposite side of the “side lay” and could be up to 2 mm.
3. The “expansion” is exactly the same for the whole side, from the gripper to the top of the sheet.
4. The biggest problem on the alignment is observed in the first 10 printed sheets and the last 10 printed sheets. During printing and at least after 100 printed sheets the difference in the alignment is smaller but the marks are still not perfectly aligned. Meanwhile, you can find in between sheets that are not aligned at all..
5. We have observed that the printing surface (registration marks) during the first pass has expanded in both edges (left and right) of the sheet.
6. We have verified that there is no problem in registration arising from the two units (1st and 2nd printing towers).
7. When printing on the 1st unit (1st pass) and then printing again on the 1st unit (2nd pass) with the same plate, we have observed the same problem.
8. The “expansion” is observed also in papers of of 250gr, 300gr and in sizes less than 50x70 e.g. 35x50
9. The paper used is the same type and brand of paper used in all previous years before this problem came up.
10. We have tested many types of paper of different thickness and we have always the same problem with some minor differences even in very thick papers.
11. The printing area temperature is normal.
12. We have changed the rollers a month ago, in order to reduce the ratio of water on the sheet so that there is no “expansion” of the paper.
13. The technicians have checked the timing on the gripper.
14. We have performed many tests with different qualities of PH and alcohol.
15. We have tried to regulate the pre-dampening.

Thanks in advance

Christos Leridis

 

would changing the back pressures on 2nd pass help ? just an idea Had this problem on a komori 2 col and adjusting pressure helped

 

Make sure the paper is not short grain i.e. the grain should run with the longest side, you can test this by ripping the sheet in both directions the cleanest tear will be your grain

Good luck

 

are your blankets corectly packed and tightened and have you checked the feeder timming
hope you can get this problem resolved' had a similar problem on a 40 inch roland thresh bearings were bad
good luck

 

leridis
So you have a fan out problem, how long have you had this press? Did it print proper before? Has the press been moved four months ago? I didn't read that a packing guage has been used to measure the blankets, very import when problems araise(I bought one because many companies that I work for don't see it to be important, ya right). Also I didn't read anything about checking bearer pressures, any problems four months ago with sevro motors by chance. And you need to find how low you can run the water, or as I call it the scum line, print some with it starting to scum and then run them through again, do you still print long when you know that you don't have enought water, if so it's a pressure issuse, not water.
FSA

 

I can't see how this has any connection with your problem at all. Expansion of the paper you get only on the upper edges of the paper mostly due to short grain paper. However a small expansion on the upper edges is normal, as in Greece is super hard to find long grain paper in your printing size. But that's another pain full story.

From what i understand your problem should be at the feeder.
Has the technician checked the timing of the paper as it reaches the front lays?
Has he tried to adjust the Front lays and the grippers? There is also the cam followers on the swinger.
There is a lot that could mess up the registration in the feeder.


My opinion, start simple by resetting the feeder (if you haven't already)

Good luck

 

Don't know if that press has a sheet compensator on the ranger drum or whether it even HAS a ranger drum, if it does, you could adjust that?

 

Many thanks to everybody. I have checked everything you told me and the technicians told me that from the technical part the machine is ok. I print short grain paper because in Greece I can't find long paper grain in my printing size. But I used to do it very long before the problem. Now I changed the dampening rollers even the metal roller in order to work with low water. The problem remain the same. We also found that the place humidity is 38%. The damp of the paper is low and when I print the first side the paper takes more water where it's needed and the result is the paper expantion. In that point I wonder why I don' t have the same problem with the my other machine where I have machine Shinohara. I use the same paper, the same chemicals etc. to both machines. Now I will buy a machine to increase the place humidity. i don't know what else to do. Anyway many thanks to everybody.

 

@ NotAGooner: You are right. I'm not sure either. I had similar problems on my machine CD 102 with completely different feeder than My Leridis machine.

How could this be a water problem!?

Still even with different system and everything it makes perfect sense that something is going wrong, before the paper reaches the first impression.


Good luck

 

Hi,

did u checked the Feeder 100%? It must be from the Feeder (because of your point 7), What is with the Suction Belt and the Suction Wheel and the Venturis, did the get enough suction air.
And have u got the problem also by the smallest sheetsize?

Hope u will find your problem

cu