Weird scumming on Heidelberg SM74

Currently operating on Heidelberg sm74 and scum on magenta is eating my brain.
It's ok on small size but when a job is printing on full size that is 740mm paper, scumming appears on the operating side and from middle and below on the edge of paper. But ink is washed next to scum from top to bottom.
All the rubber rollers and form rollers are brand new except for Water form roller and Pan roller. Which I guess is a culprit right?.
What should i do replace water form roller and pan roller??

hello, just let me know how much alcohol you add into fountain solution?
If the alcohol in the printing press is reduced, the properties of the dampening solution and thus the entire printing process
change significantly. The viscosity of the dampening solution decreases, while its surface tension increases. This significantly changes the dampening solution transport in the machine and makes the ink-water balance more unstable.

I guess you are loosing print-stability very often and fast after starting to print. What is the pH-value in the fountain solution actually showing?
At first glance, it may appear that the dampening rollers need to be replaced, but first of all, you need to check how good or bad the fountain solution is.(!) Did you have the oportunity to measure pH- and conductivity-value of the fresh water and fountain water?
What additive is in use?
How is process setting-up new mixing of fountain solution and how the printer is working?
What hardness (dH) the fresh water do show?
I am fairly certain that if we improve the fountain solution settings, it will not be necessary to replace the dampening rollers.

Question: How do you obtain new rollers in your country? Which manufacturer/supplier is accessible to you? Should we attempt to obtain new dampening rollers here in Germany?
If you could send me photos of the dampening rollers, that would be helpful for a more in-depth analysis.

Felix Böttcher GmbH & Co. KG its much cheaper than Westland what new machine have.But we have were i come Slovenia very good companies for rollers

Best Luka

Joe Burger said:

hello, just let me know how much alcohol you add into fountain solution?
If the alcohol in the printing press is reduced, the properties of the dampening solution and thus the entire printing process
change significantly. The viscosity of the dampening solution decreases, while its surface tension increases. This significantly changes the dampening solution transport in the machine and makes the ink-water balance more unstable.

I guess you are loosing print-stability very often and fast after starting to print. What is the pH-value in the fountain solution actually showing?
At first glance, it may appear that the dampening rollers need to be replaced, but first of all, you need to check how good or bad the fountain solution is.(!) Did you have the oportunity to measure pH- and conductivity-value of the fresh water and fountain water?
What additive is in use?
How is process setting-up new mixing of fountain solution and how the printer is working?
What hardness (dH) the fresh water do show?
I am fairly certain that if we improve the fountain solution settings, it will not be necessary to replace the dampening rollers.

Click to expand...

Hello Joe,

In response to your questions above, I would like some advice on the following please:
(we are running two Heidelberg Speedmasters - a 10 Colour and an 8 Colour - Our Technotrans is set to run at 10 degrees Celcius

1. What is the ideal ratio of Fountain Solution: IPA : Fresh Water ?

2. What should the pH of the mixed solution be?

3. What is the ideal CONDUCTIVITY VALUE ?

4. How do we measure the HARDNESS of our fresh water supply?

Your feedback would be greatly appreciated.

Kind Regards

Shawn

1. Not all water is the same
Many printing companies draw water for dampening solution production from the drinking water supply without knowing exactly what it contains and how it affects the printing process. This can result in quality losses or printing problems, the actual cause of which often remains unknown. Targeted water treatment can remove many disruptive factors from the water.
The pH value of fresh water is generally set in the range of 6.5 – 7.2pH, and its density (conductivity) should have a value between 300 to 450mS.(micro siemens) The hardness of the water should now reach a value between 8 to 12°dH (german hardness) and we provide a value of 10°dH.
2. what should pH of mixed fountain should have
in offset printing (UV and conventual) we should have a pH between 4.8 to 5.2. Mostly we try to have 5.0, in UV printing we shall have 4.8 to 4.9pH
3. The conductivity of the fountain solution depends on many factors. We aim to maintain the conductivity of a prepared mixture of water, additives, and alcohol at a level ranging from at least between 800 micro-siemens to 1,200 micro-siemens. This value, when the mixture is fresh, serves as a reference. If this value increases by +1,000 micro-siemens, it is a sign that the solution should be renewed.
4. There are various devices for measuring hardness of water. You shall find more information in web.
Print quality starts with the interaction of the inking and dampening system: Consistently good results assume a stable ink-water balance. Precise adjustment ensures thin and equal distribution of the dampening agent film on the printing plate.
A responsible printer checks the adjustment of all rollers (ink- and fountain) every three months and adjusts in line with the operating manual.
Good luck.