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]

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.....

 

[Printservedigital]

Ok Hessel, sounds like a more serious issue.

Please provide more details

What

CTP are you using
RIP ?
Laserpower setting ?
Chemistry ?
Processor ?
Gum?


Have you used a step wedge?
Has the laser power at the bed face been tested?
Have you recorded and tested the PH level and bath temperature?
Have you checked the brush settings?

Hagars advice was a good starting point.

 

[Hessel]

Well we are using the Lap-v, Polaris-xtv, LP82 ultra dev machine, l5000b/l5300b chemestry.
But the problem sounds the same.

 

[Printservedigital]

I trained on the XTV and have experience of running violet for 3-4 years. Been to a few places that Run Lap-V , They had very messy processors.

Where are you based.

 

[Hessel]

We are based in Emmeloord in the Netherlands.
All Agfa's technic people have been here, checked the LP82, polaris... but everything is ok. It is a very strange problem, agfa tells us we are the only ones but i know other sites who have (had) the same problems.

 

[Printservedigital]

Is it intermittent? do you record which Press/tower you run blind on?

Do you run more than one CTP line ? If so do the plates that run blind come off the same line?

You need to make sure it's def a CTP issue first before you go any further with the problem.

 

[Printservedigital]

"All Agfa's technic people have been here, checked the LP82, polaris... but everything is ok"

Listen, I worked as an Agfa Contractor, am Agfa Engineer trained in CTP installation and service (Not the two day operator training) , at a printhouse I once worked at they changed onto new chems once and said it was brilliant chemistry cleaner etc etc had no other probs elsewhere blah blah blah

Only it leeched the silicone outta the rubber and caused no end of problem (no other plant had the issue) I cannot tell you how many times I've heard that in the industry in ten years of working with Afga kit.

They ended up changing over 120 (approx) rollers in three processors. We used over 6000 plates a night!!! I've corrected agfa's fairytales before now.

I'm not saying it's an Agfa issue but please realise if you really want to get to the bottom of the issue taking everything your supplier says as read is not going to help you solve your problem.

 

[Hessel]

We have 2 presses, the problem is on both presses all over the press. We have 2 ctp lines and the plates from both lines are blinding. We did a crosscheck, plates from one imager developed in the other dev machine. Fresh chemistry before a longer run... no change..
Other brand blankets, ink, fountain sloutions, paper.... you name it.
And we tested on Kodak Thermal news Gold plates without isseus...

 

[Printservedigital]

Do you cross reference batch numbers on the back of the plate against issues?

Do you cross reference BATCHES against shift patterns??

Do you check the Developer PH IN BATH?

Have you checked processor Brush tensions? IN BATH?

Are you running yellow light conditions?

See where I'm going here?

 

[Printservedigital]

Describe what you mean by going BLIND, is there a pattern or is it patchy as in the traditional sense??


Here is what I would do

Cross reference Batch against issue.
Cross reference Shift pattern against BATCH and ISSUE (Eliminates operator issues)
Check if Agfa have checked laser power output ON BED. (This can be done through the test menu)
Check Brush Tensions in processor
Check PH & Temperature of DEV in Processor
Take Step wedge at start of every days production
Take heat test (4th plate) start of every days production.
Check on bed Laser power.

The more information you have to hand the easier the source is to detect

If you want to discuss further I'm happy to provide consultancy as a previously Agfa trained prepress technologist with a individual report.

 

[Hessel]

Do you cross reference batch numbers on the back of the plate against issues?

1* Do you cross reference BATCHES against shift patterns??

2* Do you check the Developer PH IN BATH?

3* Have you checked processor Brush tensions? IN BATH?

4* Are you running yellow light conditions?

See where I'm going here?

1* Yes it seems to be connected to the plate thickness also and the plate already looks "cloudy" out of the box.

2* Yes that's ok.

3* There is no brush in the LP82.

4* Yes, we are running yellow light conditions since we use the Lap-v

We have made a list of things we already tested, it is 2 A4 pages long.