heidelberg sm 74 2 colour 2005

Recently new with this machine.
First time with offset printer.
Having problem with it marking front edge of sheet as shown in he photo if you look closely.
As far as I can see it is damping related.
Starts the run okay with normal damping settings but after a 2/3 thousand sheets it starts to appear.I then turn up damping which gets rid of it for another cpl thousand but the problem comes back.It gets to the stage there is to much water going unto it to run the job.
Have checked roller settings etc and all look fine to me.
Would appreciate if anyone could point me in a direction please
Thank you

 

Are your water tank temperature correct.check super blue nets are ln good condition.make sure 1st form rollers are not bouncing

 

Doesn't look like scumming. Is your blanket tight enough? Correct packaging etc?

 

Dear Ali,
Is it at the lead edge or the tail of the sheet?

 

Assuming that all your roller settings are ok I would suggest that instead of increasing the damp speed that you try cleaning the plate with either some AGE rubbed deeply in a circular motion, or some other form of plate cleaner. Upon cleaning you will want to immediately roll up the plate and resume printing. If the issue disappears for another 2 to 3 thousand sheets without having to increase the damp speed then I would be looking at platemaking. Either the exposures or how the imaged plate is processed!!!

 

but why would it be just the leading edge if a plate making problem

 

It is just the leading edge

 

The form rollers are good and not bouncing.
The superblue is fine.
Not sure about fount temperature though.
I am going to renew fount and clean before next shift.

 

Checked packing which is fine.
Tighten blanket ,even changed blanket but still it continues.

 

Did you face the problem in both units?
If yes, check out your dampening fridge, clean, mix up new water with the desire IPA and fountain solution. (I assume that the quality of IPA and fountain solution is good).

If NO you have to double check the adjustments of your rollers.
Readjust your dampening from roller at the minimum contact with plate, no more than 4mm.
All the best,,,

 

Is it happening on any stock you run?
Is that strip all the time on the same place or it's moving?
Is it ok after cleaning the blanket and then start to appear after couple of thousand?
Vario on or off?

 

Allistar. Make sure your ink forms are not oscillating.moving back and forth.

 

For the same reason that streaking and roller marks happen on a press. The plate processor applies its various chemicals via a series of rollers and side to side scrubbing action.

 

But it is a ctp machine using laser

 

Vario on.
It happens just on leading edge on any stock.
happens just after cleaning the blanket ,even changed blanket to a new one.Still does it

 

Have done this and still does it

 

I presume that you've tried with vario off and there is no difference (?)
I'd try to set ink form rollers to 2mm damper to 3 mm and give it a try