Colour dots

[Alistair Tinsley]

Printer ,2 colour 2005 Heidelberg SM 74.

What would be the cause of the dots on the solids as in Photographs?
All new rollers, pressures all fine etc.
First run Blue you can see start of it .
Both units doing it.
Is this ink related,damping ,etc.
Any help appreciated.
Machine quite new to myself
Thank you

 

[junker1984]

Often caused by oil/grease spatter, originating at a leaking cylinder bearing or oscillator seal.

 

[Alistair Tinsley]

This was the next job on after I greased the machine. I did all the nipples.
Would it be possible that it was grease spatter?
I have given machine a good cleaning.

 

[junker1984]

Could very well be. I’ve seen the same issue many times, mostly caused by oil leaks, though.

 

[Jack liston]

Go through the the machine wipe down excess grease.also did you try a different type of paper?

 

[Alistair Tinsley]

I have cleaned all the machine cylinders transfer cylinders etc
It only does it on silk board.
If I turn it over and run it on other side which normal offset it does not do at all.
I am thinking its paper finish but what can you do?

 

[Alistair Tinsley]

I am now discovering the the blue net on delivery transfer cylinder is non existent.
This could be part of the problem so going to replace that.

 

[Jack liston]

It definitely will also try to reduce ink if ink is too stiff it will pull the fiber off or try better stock

 

[Steve F]

Oil and grease splats would appear as white spots in the image areas, and come and go in different places, every few sheets as the ink takes a little time to overpower the oil/grease.

Your problem is definitely the super blue nets.
Correct me if I'm wrong (old age...) but if you're talking about the final delivery transfer cylinder, the one with the segments, the sheet actually goes over the top of that cylinder so the bottom of the sheet touches the net. Hence why yours is old and tatty, the same as every other one I've ever seen, as there's little need to replace it.

Changing the other nets is a bit of an art form to get it not too tight and not too baggy.
As a quick fix from job to job get a strip of sticky foam insulation, cut into small bits and guesstimate where to stick them on the super blue so they are in a position so they touch a non image area on the sheet, and therefore stop the areas marking, touching the net.
Remembering to remove after use...
Or just buy a CD/XL!

(as an aside after greasing oiling the press, run it at high speed for a while, then clean blankets and imp cyls, that'll get rid of nearly all of it)

Steve

 

[Steve F]

To add:
The best way to guesstimate where to stick the foam on the super blue, is to get a printed sheet, inch it back through the press and when it gets through the unit, hold the sheet up against the imp cyl and keep inching until the area you're getting the marking is very close to the super blue.
Minding your fingers...

Steve

 

[Alistair Tinsley]

Thanks all.
Will have the silk paper on again on Monday.
So will take all the advice on board and see how we get on

 

[Adil]

Hi ali .
Do you use the same plate on the other machine ??

 

[Adil]

Does this problem appear on the first sheet or on each sheet? once the machine stops. Have you tried to prepare the plates and print then check after the preparation with the plate preparation solution

 

[Adil]

sometimes the problem of pitting the plates presents itself in this way, and it is because of the mixing of the dampening solution, too much or less additive, or the expiration date of the plates has passed

 

[Alistair Tinsley]

Would that cause this as the marks are on the plate?
Thanks

 

[Alistair Tinsley]

Does this problem appear on the first sheet or on each sheet? once the machine stops. Have you tried to prepare the plates and print then check after the preparation with the plate preparation solution

Each sheet.
Tried all sorts of cleaning

 

[Alistair Tinsley]

Sorry for so many silly questions but learning as I go along.
What would be the cause of this on the front 70mm or so of the sheet when full block or colouri g all of the sheet?
Thank you for all help

 

[Mehanka Abortmaher]

@Alistair Tinsley
Attach the paint rolling shafts to the clean form, the instructions for the machine usually indicate what width of the strip the shafts should leave on the plate. This is very similar to templating (wear or incorrect adjustment of colorful knurling shafts)
In case of malfunctions of bearings, pneumatics and removal levers, the shafts can "jump" from hitting the edge of the plate.

 

[Alistair Tinsley]

Will check this out

 

[Raf77]

Are the dots in the same positions during the run or they're moving?