SM52 - Scumming on the Magenta Printing Unit Only

Hello everyone,

I have a problem on my Heidelberg SM-52, the 3rd Printing Unit (Magenta).

1- I have replaced all Printing Units inking rollers and performed the installation according to the manual. All rollers were set to the exact measurements as the manual.
2- The dampening solution is with a 3% fountain solution, 8% IPA and 89% Distilled water, temp 10 degrees, conductivity 1400 us, pH 5.0.
3- The CMYK inks im using are from Sunchemical.

Everything looks great until I start printing, scumming occurs on the 3rd Printing Unit only, no matter the print.

For a balanced water/ink levels, the water pan roller speed for all rollers is about 40-50%, the magenta goes up to 85%.

Can you please advice....?

 

Maybe look at the rams to make sure all is working correctly.
Is the scumming on 1 side only or all over?
For it to be just happening on 1 unit makes the solution mix unlikely.
Why are you using distilled water?
Just double check the setting of the pan roller to chrome & chrome to plate damper.

 

The problem is most likely in your dampening roller settings, especially if the problem just developed after changing your rollers. If the settings are too tight, there can be some binding when the rollers come on which causes incorrect or uneven dampening.

 

Have you tried to print another color ink in that problem unit? If you tried another color and it had the same problem, and your certain that all rollers have been set correctly, I would advise to check durometers of all rubber dampening rollers. You might also want to be certain that the water level in the pan is the same as on the working units. Another thing to check would be that the water pan is not installed too far forward. Not sure of how the baby Speedmasters are set up, but I know that its possible for the water pans to be installed wrong on the larger presses. If your installing the pan too far forward into the press, you could encounter a problem where the neoprene rubber insulation on the pan is having a squeegee effect on the water distributor roller. This would have you needing to run the motor speeds up higher. Its also common to see this rubber insulation peel off and separate from the stainless steel pan, and have the same squeegee effect.

 

On the SM52 the pan roller can only be installed in 1 position

 

if all other 3 units working good, why not just switch all ink and dampening rollers with any of those 3, and see if that works

 

Labor intensive? Maybe?

 

Thank you everyone for your suggestions.

The problem was fixed by replacing the plate dampening roller between the 2nd (Cyan) and the 3rd (Magenta) Printing Units.

The problem on the 3rd printing unit was solved but the issue did not pass to the 2nd PU.
What is confusing me is why the problem did not follow the roller? even though the rollers settings were 100% as required.

 

Are you aware of any air leaks on the problem unit? Is your press equipped with air curtains blowing air down onto the back side of your inker. If you have the air flow turned off on all the other units, but its blowing on the problem unit pretty hard, it would require a higher damp motor speed.

 

Try integrating and segregating the dampening system. Sometimes the problem is with the Z roller setting.

 

Air was leaking as soon as the dampening system is pressed on the plate and has been fixed. But it wasnt the issue.
I agree that air leakage can evaporate the IPA and help in drying the dampening solution which requires a higher damp motor speed to compensate the loss of water, but that wasnt the case apparently.

Thanks tho