Vertical Lines In Printing Sheet Cyan + Magenta Only

[TSERTOS MASTERGRAPH]

Dear colleagues hello .
I would like to ask you if you can help me with a problem we have in printing .
We print in a KBA RA 104-4/1997. We have new rollers in the units ( dampening and printing ).
When we have to print big areas ( not light raster, but 100 % ) we find some vertical lines ( not horizontal ) in second and third unit ( cyan + magenta ).
Would you give me any ideas / advices ?
Has anyone meet this problem again ?
We changed a metal chrome cylinder ( the 110 diameter, beacuse we thought it was that ) but nothing changed in prinitng, still have this lines...
All answers are acceptables...
Thanks in advance

 

[SteveSuffRIT]

Can you provide photos?
You use the term "lines". Do you really mean "streaks"?

 

[Erik Nikkanen]

Dear colleagues hello .
I would like to ask you if you can help me with a problem we have in printing .
We print in a KBA RA 104-4/1997. We have new rollers in the units ( dampening and printing ).
When we have to print big areas ( not light raster, but 100 % ) we find some vertical lines ( not horizontal ) in second and third unit ( cyan + magenta ).
Would you give me any ideas / advices ?
Has anyone meet this problem again ?
We changed a metal chrome cylinder ( the 110 diameter, beacuse we thought it was that ) but nothing changed in prinitng, still have this lines...
All answers are acceptables...
Thanks in advance

I am curious about your lines. Are they very narrow and close together? Could they be due to "ribbing"?

Back in 1985 to 1992, I worked at a company, Tetra Pak, that had Chambon web presses. The press continuously printed with "ribbing" in higher coverage. The problem was that this press was designed with no oscillating rollers in the upper part of the roller train. All the oscillating rollers were in contact with the form rollers. In general, higher coverage will result in thicker ink films in the upper roller train. Thicker ink films result in ribbing as the ink film separates just after the nip, and the main way to get rid of ribbing is to have oscillation smooth them out.

It also matters how the path of ink goes down the roller train. If the main path goes through more points of oscillation, that should reduce the ribbing.

At our plant in Canada, the improvement of that problem was to take out one of the rollers in the roller train. At the Texas plant, they solved the problem by adding an oscillating roller in the upper part of the roller train.

If ribbing is the problem you have, maybe rollers are not set as properly as you assume. Might be a good idea to check and make some adjustments.

 

[Joe Burger]

In my work as a printing instructor, I often deal with these problems.
Practical measures to minimize or completely eliminate torsional streaks are as follows:
1. Correct adherence to the specifications for adjusting the inking and dampening units according to the manufacturer's instructions.
2. Correct adjustment of the dampening solution, taking into account the pH value and alcohol content as well as the cooling
temperature of the dampening solution.
3. Regular cleaning of the roller frame with a special paste to reduce limescale deposits.
4. Reduction of ´lateral play´ on the application rollers within the bearing shells.
5. Immediate replacement of worn rubber rollers and regular visual inspection of these by the printer.
6. Immediate replacement of damaged bearings on rubber rollers and oscillating rollers.
7. Correct adjustment of the cylinder package on plate, rubber, and impression cylinders.
8. Adjustment of an optimal ink-to-water balance during production.

Furthermore, the machine operator must pay particular attention to the following points:
1. Ensuring correct pressure adjustment between the plate and rubber cylinders. (Note lift strengths)
2. Ensuring correct pressure between the blanket and impression cylinders without overpressure effects.
3. Frequent replacement of the blanket and backing sheets; a torque wrench must be used when mounting.

It seems reasonable to assume that the effect of the torsion stripes could be caused by the mechanics of the printing unit, particularly in the area of the oscillating friction rollers.

 

[Joe Burger]

If the oscillator rollers are looking like the picture .... clean these parts.
In some cases, the following measures can help reduce streaking:
1. Ensure the correct pH value, which must be between 4.8 and 5.0 pH.
2. Clean the ink unit regularly with a special paste to eliminate calcium buildup.
3. Eliminate lateral play of the application rollers.