Thin lines along the plates. CTP Kodak Trendsetter III 800.

[vaks1166]

Hello, everybody!

We are facing the following problems in our CTP Kodak Trendsetter III 800.

Problem.
There are sometimes (quite often) thin lines on the plates going parallel to the short side (790 mm) of the big size plate (790*1030 mm). So the lines are perpendicular to the direction of the head movement.

Sometimes these lines are not seen well or even do not present at all but usually they are always present and it happens that the whole plate is covered with such kind of stripes from one side to another. They go as well through all images on the plate and it looks like the color of these lines is 100 percent, because they are “not seen” on 100 percent color bars. So the lines are seen on prints as well.

Although on the photos the lines look like black in reality they have the color of unexposed plate, they are absolutely blue like the stripe under the magnet clip.

They are especially present at the beginning and at the end of the plate.

The distance between the lines is always constant and is a little bit more than 2 mm.

To get rid of the problem we:
1) have increased the power of the laser;
2) have extended the time of the development in plate processor.

It helped to solve the problem for a short time but eventually the lines come back from time to time quite often.

Who know the cause of the problem and the ways to solve it.
The head? — But sometimes plates are absolutely perfect.
The temperature? The humidity? The voltage? The developer?…

Thank you very much for all your comments and advises.

 

[prepressdork]

This is a shot in the dark but perhaps the laser is out of alignment where individual beams are either overlapping or there is a gap between each swath? Again, total guess.

 

[vaks1166]

This is a shot in the dark but perhaps the laser is out of alignment where individual beams are either overlapping or there is a gap between each swath? Again, total guess.

Thank you very much for your opinion!
But how can it explain the fact that sometimes these stripes are seen slightly, sometimes very well and sometimes (but rarely) the plates are absolutely perfect.

 

[prepressdork]

That I cannot explain but I just had another thought. When we switched to the current plate we are using, we were told that our older platesetter (circa 2008) may not be compatible because of how the laser optics module was designed leading to a possible light leak. As I am not familiar with Kodak platesetter, please forgive my ignorance but is your platesetter older and you are using a (much?) newer generation of plate?

 

[carlossc_73]

Send me PM if you haven't solved it

 

[Magnus59]

The lines look too close together to be a laser focus or power problem. Try applying some light silicone oil to the lead screw and see if the problem goes away as this can be caused by a dry lead screw.

 

[vaks1166]

Hi everyone!

Thanks a lot for the ways you’ve suggested to solve the problem with the lines!

But fortunately (or unfortunately) I had not possibility to apply them as the lines has unexpectedly disappeared. At least there are no lines for two last days.

But strange spots have appeared instead of the lines. Usually they are closer to the margins of the plate. The spots have unregular shape and their size is about 1--3 mm. And they come out on about every 3rd plate.

I've never seen the spots of this kind before, so who knows what is the nature of such kind of spots?

Dirty rollers in the processor? New plates' feature? Have no other ideas…

Thanks a lot in advance!

 

[Magnus59]

Hi everyone!

Thanks a lot for the ways you’ve suggested to solve the problem with the lines!

But fortunately (or unfortunately) I had not possibility to apply them as the lines has unexpectedly disappeared. At least there are no lines for two last days.

But strange spots have appeared instead of the lines. Usually they are closer to the margins of the plate. The spots have unregular shape and their size is about 1--3 mm. And they come out on about every 3rd plate.

I've never seen the spots of this kind before, so who knows what is the nature of such kind of spots?

Dirty rollers in the processor? New plates' feature? Have no other ideas…

Thanks a lot in advance!

Are these positive or negative plates?
My theory is: Somebody has lubricated the lead screw, resulting in the lines going away, however, they applied too much lubricant, which is now flying off the lead screw onto the surface of the plates. Of course I may be totally wrong

 

[vaks1166]

Are these positive or negative plates?
My theory is: Somebody has lubricated the lead screw, resulting in the lines going away, however, they applied too much lubricant, which is now flying off the lead screw onto the surface of the plates. Of course I may be totally wrong

Hello!
Your hypothesis is beautiful!
The plates are positive.
And thanks a lot for your comments.
But I still have no feasible ideas about the situation))

 

[MacTwidget]

I have seen these symptoms occur if the focus was even slightly off.

 

[Johu]

Hello, Looking at the new spots, I think that Magnus is on to something. If it would be processor it's hard to imagine them being so oddly shaped. As Magnus said they look like something has spilled on to the plate. On which side are they usually on? You wrote that they are mostly in the margin area, but on the lead/trail edge or the sides?
If they happen as often as you wrote (~every 3rd), it might be good to stand where plate goes from the recorder to the processor and have a look if these spots are visible (liquid of some sort or anything unusual) before they enter the processor.

 

[vaks1166]

Hello, everyone, again!

Thank you for all your comments!
They all were very useful and let me think deeper about the whole process.

I hope (or at least it looks like) that we have no more these kinds of problems.

About the lines.
We use Double Layer Thermal CTP Plate (positive).
It looks like the cause was the plates. The whole batch of plates (several boxes) had this problem.
We’ve started to use the new batch (the same supplier, the same name of the plates but different batch) and these plates were absolutely perfect — no lines!
I have noticed only two differences between the plates of these batches.
1) The bad ones have more violet top layer, the new ones’ top layer is more blue.
2) It looks like the grain of the bottom (aluminum) layer of both batches is different.
In the bad ones the grain goes in the direction perpendicular to the axis of the cylinder of the imagesetter. In the new ones the grain goes along the axis of the cylinder of the imagesetter. If I define the direction of grain properly, of course.
But I still can't imagine how all these factors made the appearence of the lines.

About the spots.
The spots have appeared only on the new plates from the new batch but for the moment I do not see them any more. So I hope they have disappeared forever.

And we haven't greased the lead screw...
I don't know how to get access to it(( Is it possible to do without our service engineer?

Thank you again for sharing your opinions on the topic!

 

[carlossc_73]

Told you to write me, so I can give you the help to solve it. It might be that your pressure roller is dirty, that's why you have this new spots.