New batch of violet plates

[nilay]

Is it essential to do test on each new batch of violet plates ?

If yes, then which kind of test we should follow and how it should be useful to us ? Examples: Stoffeur, Expose solid, apply Acetone etc..

Thanks a lot in advance for your help.

[hagar]

Originally Posted by nilay

Is it essential to do test on each new batch of violet plates ?

If yes, then which kind of test we should follow and how it should be useful to us ? Examples: Stoffeur, Expose solid, apply Acetone etc..

Thanks a lot in advance for your help.

I would say this depends, on type of work you are doing and type of plates.

If anything I would say check RIP calibration with Dot Meter and recalibrate if needs be. That is a quicktest and will compensate if there are difference

Differences between the better brands are minimal, but beware of old plates and plates which have been cut down by 3rd parties.

If you want to do the full QA on your system once in a while its also worth checking PH and preheats on processor and laser power on the CTP device

[VladCanada]

Quick and easy way for visual control - Digital Control wedge/strip (*.eps file) attached to every job page/color at non-printable part of plates.
Just look at first plate from new batch after imaging and processing, and you will understand you needs of new calibration... or may be not.

[maxon]

nilay,
You must ask the plate supplier for details. Each plate manufacturer has its own set of rules regarding routine calibration. If it's normal violet photopolymer plates such as LP-NV / N91V / N92V / VioletPrint then you should use the usual analog plate step wedge, Stouffer on UGRA PCW 1982 to precisely determine the laser exposure level. As said before, batch to batch variation is usually small. Always bear in mind that environmental conditions can affect plate sensitivity to a certain degree: you must keep the plates at ctp room temperature within the prescribed interval, also humidity is important. Follow CTP manufacturer and plate manufacturer instructions w.r.t. environment, well, it's common sense anyway for whatever CTP you might have.
We measure our colorbars on plate when a new batch arrives. If percentages are out by more than 3 percent we run a stepwedge calibration to check the plate sensitivity but it rarely needs adjusting. It's more important to keep the plate processor clean and chemistry within normal parameters, we normally don't change exposure level or RIP linearization. Keep processing conditions constant to ensure trouble free consistent work.

[nilay]

Thanks a lot for your quick replies. We are checking the Laser power once in a month but not with new batch of plates.

[DonBlock]

Depending on which CTP you are using will also depend on how much the exposure level will change as much as the plate manufacturer. Also, each system is going to be slightly different. You need to test out your system and definitely use the Analog wedge for your test. The laser Has To go physically through the wedge to get a proper reading. Be aware that when they ask for a solid, it does not to be mean as solid as the the fully exposed plate. This will be overexposed! There is a tint there and it should be solid in appearance and you should slightly see the number. It is worth a plate to check each batch instead of hoping it's good and waiting pres time. ( Use your thermal strips on the back of the test plate at the same time to verify the pre-bake temp. And of course, don't try to extend the life of your chemicals. Follow the recommended life of the manufacturer. It will save you a lot of headaches.

[Hessel]

With Agfa it's always a surprise when you open a new box or batch number. Every box i start with i always have to change the laser intensity. We use Lap-v plates.

[Printservedigital]

"With Agfa it's always a surprise when you open a new box or batch number. Every box i start with i always have to change the laser intensity. We use Lap-v plates."


Must admit this is becoming more of a problem with Agfa Plates.

I've seen the 50% on plate range from 52 - 80% over different batches of plates.

[Printservedigital]

"Use your thermal strips on the back of the test plate at the same time to verify the pre-bake temp."

Not a good idea as the plate is then raised from the flatbed, Also you don't get a true preheat reading until the 4th plate has gone through as latent heat can affect the first and second plate.

I've seen the effects of a problematic preheat on plate temps.

[Hessel]

At this moment we are having a lot of problems.... it started about july/august 2008.
Blinding etc.....