Azura plates

[lesliegroenewald]

We are using Azura TS plates and expose them in a Screen Plate Rite thermal.
Processing unit is a Adara TH85 with Azura TS Gum
We experience at random intervals that multiple lines spaced 1.5mm appart appear on the print more or less on the top half of the printed sheet.
At closer inspection it looks like dirt. You cannot see it on the plate, only when you make you first pull. It is in all the colours and form a nutral grey image on the print.
You can remove these lines by washing the plate with plate cleaner.
Please help

[Raymond Ramirez]

In my experience with the TS Focus and Zoom are real critical. Do you know what your settings on the imager are set to?

drum speed, power, focus and zoom?

Ray

[lesliegroenewald]

Hi Raymond

Thanks, we wil check all the things you mentioned

Leslie

[w3112]

Hi,
I am a little bit confused here. Not sure if we can help , but I like to share my comments anyway.

The Azura plate is a negative plate.
So the image area is the part that is really exposed by the laser.
If there is no laser light, there will be no image. Never.
So it will be difficult to "repair" a missing part of the image with a plate cleaner.

The PTR settings are indeed important.
Incorrect focus will result in runlength issues. ( again something that will not be repairable )
Incorrect zoom usually shows up as fine lines. Depending on the technology , that will be at fixed intervals of 0.33 mm or 0.64 mm or 5.12 mm ( approx . )
There is no PTR that has a "beam width" of 1.5mm.

None of the engine settings is for the "top half of the plate only".
You might have mechanical issues, causing the plate to lift from te drum.
But this creates an out focus condition that will show up as white area´s.
And inside the PTR , there is a sensor that will detect this plate lift.
And there is a drum vacuum sensor that will detect air leakage too.

So I wonder how your platesetter could be the "cause" of this problem.
I would definitly look into other area´s like plate , processing and printing too.

Regards
w

[lesliegroenewald]

w3112

Thanks for the comments.
We are currently looking at the whole system. An Engineer from the supplier is busy right now.
We have done various tests to eliminate most obvious areas where lines could be generated.
We have developed the plate vertically and horizontally, but the lines remain in the horizontal position.
The lines are on the print of both our presses in the same position. However yesterday the lines were in the bottom half of the print.

I will keep you updated as we go

Leslie

[w3112]

Hi Leslie,

Here is something we have noticed in summer last year.
- the lines are in the non-image area, and can be removed with plate cleaner.
- they are approx 200 mm from the edge of the plate, and run in the "production" direction of the alu coil.
- rotating the plates 180 degrees before exposing makes the lines go from "top" to "bottom" on the plate. ( so excluding the CTP device )

Our problem disappeared when we started a new box of plates.

w