plates not cleaning up

[kwikford]

Hello, we have an issue with only the black plates not cleaning up on start up with our press. Everything was fine until about 3 weeks age. It started with the half tones during the run and now when we start up, we have 2-4 pages that won't clean up and cause us to shut down and remake the plates and apply finisher to the rest of the plates on the press. We have been playing with conductivity and have flushed the system before the run and cycled both tanks to 1200. One thought was me might be burning the plates out with a high conductivity. Lowering and stabilizing the conductivity helped but didn't solve the problem. We have CTP and have tried a new batch of plates and changed out chemicals. Any suggestions is helpful

Goss offset

 

[GazKL440]

I would suggest that with the problem being localized to only the black, and assuming nothing else has changed, that the boys may need to have a look at the roller settings in that unit.

IF something has changed (ie ink/chemistry etc) start with whatever was changed and perhaps swap back to the product that's been superseded and see if there's an improvement.

IF there have been more than one change with regards to ink or chemistry etc, it's important that you explore ONE AT A TIME. That way you know which rep to hassle for beers for causing you issues with their dodgy product

 

[kwikford]

I would suggest that with the problem being localized to only the black, and assuming nothing else has changed, that the boys may need to have a look at the roller settings in that unit.

IF something has changed (ie ink/chemistry etc) start with whatever was changed and perhaps swap back to the product that's been superseded and see if there's an improvement.

IF there have been more than one change with regards to ink or chemistry etc, it's important that you explore ONE AT A TIME. That way you know which rep to hassle for beers for causing you issues with their dodgy product

The plates that are not cleaning up are coming from different units, not the same unit every time. Up until Friday, we could start up with fresh plates and not have a problem but Friday we had two different runs that had 2 pages each time that wouldn't clean with fresh plates. thanks, John

 

[GazKL440]

In that case you can *almost* rule out a press (mechanical) issue, unless it's a certain group of units that are the main offenders as it's certainly possible that these units are suffering higher roller wear rates (different techs setting rollers harder/softer for example).

Being a fairly recent issue, the first thing to consider is if anything has changed: a switch of press chemicals, inks, or perhaps paper supplier? On the pre-press side have you changed plate suppliers or processor chemistry, lengthened or shortened plate processing time or temperature? As you mentioned it's possible you've got a bad batch of plates; we recently did a short run booklet that had 19 signatures and almost every bloody plate had to be hand scrubbed and about 25% of then remade. From a pressman's POV an absolute nightmare!!

So I guess if a new batch of plates doesn't fix the issue, find out if anything has changed. If so.... I'm willing to bet you will have found your culprit

Good luck.... And keep the sharp knives and short ropes away from your printers

 

[BeauchampT]

What sort of image is on those pages that aren't cleaning up?? (Do you have a picture?)

To clarify: you said you've played with conductivity; did you return it to its original settings before setting off in search of other solutions (this has hurt our press operators a few times)

 

[kwikford]

update: CTP plates still not cleaning up

update: CTP plates still not cleaning up

well we still are having the same issues. We are running rpb liquid gold around 1250 conductivity. Plates that have problems with cleaning up are mostly in half tones and have to be sprayed with rycoline recon to clean them up. We have restriped and still have
the issue. We are also running Kodak plates, could the liquid gold be a bad match for the Kodak plates? We have also set ink pressures and water pressures to recommended spec. Just to recap, this all started when we installed 4 new TKS towers to complement our 2 Goss Newsliner Towers and 3 goss mono units. One other note, we noticed that only one out of the two plates on the cylinder aren't cleaning up and tried an experiment. We ran up the press for a few minutes, stopped and marked the plates that faced toward the outside of the press. Ran back up, came down and noticed that the plates that are facing towards the inside of the unit (archway) were the ones not cleaning up. Any help is appreciated.

 

[3rd shift Bill]

What is the PH of your fountian solution? It should be 4.5 on a good ph meter. conductivity should be measured on a fresh batch of fountian solution along with PH and then you have a baseline to go from and you should monitor both. If your conductivity goes up to high 2800 to 3000 or your ph changes to more than 5.0 during a run it needs to be changed. Do you have an automatic mixer and one main tank on your press or seperate tanks for each unit? When was the last time the dampening system was flushed out and cleaned so you know where you are starting at with fresh fountain solution. Bill

 

[Lukas Engqvist]

You need to isolate the problem, is it the plate or the unit. Is it the ink or the fountain. It is also important to document changes so that you can trace what effect changes have.
Also think about if plates are stored or handled in a specific way, that may affect the plates. Is it the first plate in a batch that is affected negatively (possibly a pump that is not working as it should in developer/finisher) imaging plates in other order eg Y C M K may help make this less problematic.

Also may be usefull to know what materials you are using (brand and technology).

 

[BeauchampT]

Just to recap, this all started when we installed 4 new TKS towers to complement our 2 Goss Newsliner Towers and 3 goss mono units. One other note, we noticed that only one out of the two plates on the cylinder aren't cleaning up and tried an experiment. We ran up the press for a few minutes, stopped and marked the plates that faced toward the outside of the press. Ran back up, came down and noticed that the plates that are facing towards the inside of the unit (archway) were the ones not cleaning up. Any help is appreciated.

So, can you duplicate this one plate clean, one plate dirty situation consistently? If so, can you figure out if the areas that aren't cleaning up somehow line up with the print unit forms? It may be that with the new towers being installed, there is either a problem with the units not properly disengaging forms, or perhaps not enough air pressure in your building supply to deal with the new equipment.

As a complete other aside, have you checked with Kodak that the fount etch you are using is 'compatible' with their product? Also, is the gumming station in your plate processing line working/using fresh material. I've seen old gum being recycled in the plate making process and leading to some very odd run up issues on press.

 

[kwikford]

What is the PH of your fountian solution? It should be 4.5 on a good ph meter. conductivity should be measured on a fresh batch of fountian solution along with PH and then you have a baseline to go from and you should monitor both. If your conductivity goes up to high 2800 to 3000 or your ph changes to more than 5.0 during a run it needs to be changed. Do you have an automatic mixer and one main tank on your press or seperate tanks for each unit? When was the last time the dampening system was flushed out and cleaned so you know where you are starting at with fresh fountain solution. Bill

Hey Bill, PH is within range and we installed a meter in the quiet room and the conductivity is pretty stable from 1250-1300 during the run. We have the automatic mixers with two tanks and the dampening system has been flushed before the run.

 

[kwikford]

You need to isolate the problem, is it the plate or the unit. Is it the ink or the fountain. It is also important to document changes so that you can trace what effect changes have.
Also think about if plates are stored or handled in a specific way, that may affect the plates. Is it the first plate in a batch that is affected negatively (possibly a pump that is not working as it should in developer/finisher) imaging plates in other order eg Y C M K may help make this less problematic.
Also may be usefull to know what materials you are using (brand and technology).

I think we have ruled out the plates since it only happens on the black plates on the press but have relooked at finisher, developer, replenisher just in case.

So, can you duplicate this one plate clean, one plate dirty situation consistently? If so, can you figure out if the areas that aren't cleaning up somehow line up with the print unit forms? It may be that with the new towers being installed, there is either a problem with the units not properly disengaging forms, or perhaps not enough air pressure in your building supply to deal with the new equipment.

As a complete other aside, have you checked with Kodak that the fount etch you are using is 'compatible' with their product? Also, is the gumming station in your plate processing line working/using fresh material. I've seen old gum being recycled in the plate making process and leading to some very odd run up issues on press.

Gum is fresh and we have other shops running same fount solution with same plates. The black plates are not cleaning up on restarts and hard stops. The problem is with evident on not just our tks towers but goss monos and towers. Seems that our window for cleaning up is small and we have to fine a way to increase that window. I like the idea about the air pressure and thanks everyone for your responses.

 

[D Ink Man]

If you want to try the ink avenue, I would suggest trying a heavier body (same tack) black while still maintaining an ink that has good transfer. Ask your ink supplier, they should have a product to swap in an applicable black only.

 

[kwikford]

If you want to try the ink avenue, I would suggest trying a heavier body (same tack) black while still maintaining an ink that has good transfer. Ask your ink supplier, they should have a product to swap in an applicable black only.[/QUOTEI


Ink Man, black ink does seem a little on the runny side. Thanks for the response.

 

[maas]

Have you checked the temperature of the unit and the water?, is the problem consistent during the day i.e. at start up with a cold press as well as during the day, does it get progressively worse during the shift? Do you take the impressions off when you pull up to prevent plate staining?

if you do not have refrigeration on your water try placing ice cubes in the tray and see how this goes?, my theory being that with heat ink will lose its rheology and just turn into grease and stain the plate.

I take it you have checked your clearances and done a stripe test etc....

To isolate ink and plate clean up the Y duct and fill it with K also plate this unit with the K plate, run dummies on the K and see if the issue repeats itself ( i take you run CMYK sequence)

regards
Maas