Blinding problem

[Hessel]

We work with positive plates. I had overexposure, underexposure, elliptical dot, sublima (AM/FM) dot... But i know what you mean.
One thing i did not mention yet is that the 8 year old press the blinding starts in a corner on the tail of the plate and the 9 month old press has 1/2 inch wide lines every 1 1/2 inch.

[VladCanada]

So... clean the optics and get a proper exposure value (less than you've got now). I know that every Polaris user has an issue with the Exposure and only thing they do - increasing the laser exposure.
Do you clean the Spinner Prism facets regulary????????????????????

[VladCanada]

If you can see a dust contamination on every of 6 or 8 facets (one side is dirty than another) and if you see the blinding starts exactly on the end of scanning lines (one side of plate) - that's a sign to you, clean me ASAP!

Sure that's a Positive process, I'm sorry for the confusion (did not touch CTPs more than a year!)

[Hessel]

AGFA tells us that cleaning is not nescesairy on a Polaris XTV..... Should they clean it you think?

[VladCanada]

Does it mean the mirror is clean forewer because the top position of a Spinner? Khmmmm
It depends on the environment in Polaris room.
I have never work with the latest version XTV but the principle should be the same.

From LithoStar plates presentation file: Overexposure give shorter runs, underexposure - toning&scumming

[Hessel]

The new polaris XTV has less mirrors and the whole optical envirement is in a overpressure. So no dust can come in.

[Green Printer]

We have experienced the same effect a few times on sheetfed Komori and Sakurai. Every time the problem occurred it was ink related.

[Lukas Engqvist]

lines in the plate? Could be a deveoper issue. Have you checked that all pumps are working and that there is no build-up of chemicals making the feeding rollers jerky movements.
look for a roller/cogg with a circumfrence of 1 1/2 inches.

[Bret Hesler]

I had a similar experience with Fuji photopolymer plates. It turned out to be a press wash issue. Pressmen were using a water miscible press wash without mixing in water and without a thorough water rinse at the end of the washup. The Fuji tech brought a 2- step washup and Febo, after a few cleaning cycles alternating the products, the plates that blinded after 250 impressions ran beautifully.

Bret

[clark@colorpress.com]

We had this problem with these plates on sheetfed presses. AGFA rep said that the developer replenishment was critical. The development process is some sort of silver diffusion process and if the temp/time/activity of the developer is not optimal then we got blinding. The silver has to "go down" on the plate to use the reps words. We ended up cleaning and re-batching developer every week and our blinding problems went away.