Plate Image Wear on Web Presses

[Brian Gibson]

Hello to everyone.
I'm new to this group so I hope this is posted in the proper location.

We are having plate image wear on our web presses and I am just curious as to what others have done to correct similar problems. The image seems to be physically wearing off the plates. Mostly happens on our longer run jobs at around 100 - 200,000, but it has also happened around 40 - 50,000. Tends to show up on the print in the black first and then the magenta. Wear seems to travel side to side across the plate. Not lead to tail.
In November of 2007 we switched from Kodak Sword plates to Fuji because of wear, and other issues. At first, the Fuji plate ran great until around April 2008 when we started re-plating long run plates again. As time goes on, it seems like the length of run for the plate is getting shorter.

We are an in-house shop that prints both sheetfed and web. The web runs almost 24/6.
Plates are Fuji LHPJ 21.75 X 35 X .012.
Output from Kodak Trendsetter News 50. (2)
Processors are G&J Quartz Z85. (2)
Stochastic screening 36 micron 1200dpi.
Web presses are Goss Community 4Highs, 35 wide X 21.5 cut off, non-bearer. (4)
Ink sequence is KCMY.
Paper is Abitibi BoWater News Offset or Alternative Offset. 10" - 34"
Flint Ink CMYK, occasionally we use some recycled black, made using 300 micron filter.
Fountain solution Fuji Pressmax 14N, mixed with city water 10 gains hard and no additives.
Blankets are 66 or 67 Central with .20 Mylar pack. Plates are not packed.

Any information you can share is greatly appreciated.
BG

 

[Neil Meggitt]

Have you looked at the fount % or changing the brand / type of fount you are using on the press?

 

[Alois Senefelder]

Plate Wear

Plate Wear

Hi Brian, Plate wear nearly always is related to poor "Press Settings"
Have you Checked the Plate Cyl. to Blanket Cyl. Impression settings + all the Plate Inker Roller settings
Damper Rollers Settings !!!!!!!!!!! are all the Blankets Tensioned correctly !!!!!!

Have your Font supplier - check the "Fountain Chemistry " and how often do you "Wash the Blankets" could be just abrasive Newsprint Paper

This topic should be in the Sheet-fed forum

Regards, Alois

 

[Brian Gibson]

We have had a pressroom tech in from Fuji and he has been looking at the fountain solution.
We did change it a few months ago but the plate wear had already been happening and when we changed, it did not seem to help reduce the wear. Perhaps we need to try something different. I will check with the press crew to verify the press settings. Thanks for all the help. I'll keep you posted.
Best Regards,
BG

 

[jlind]

Brian:
I think this is the perfect place for this question.
Start checking the inks for foreign grit and debris. This can be done with a Hegman gauge, and the ink tech rep will bring one in to do the test. Simple test. As you can imagine, grit in the ink would wear plates fast and irregular if not in every batch. You running totes or kits? Is the image area wearing off or is the non image area scratching and taking ink? Is it worse where the form rollers bounce in the gap? Goes back to Alois' comment. Any way you can bake the plates to harden the coating and give longer run length...used to be the advantage of positive working plates.
I don't think plate companies are as concerned with run length any more, since run lengths are shrinking. Just some thoughts. If you have the long runs, rejoice and burn some new plates. I think CtP plates have thinner coating weights to give the lasers a better chance of making dots or spaces. This works against run length.
As for stochastic, there is that oft stated idea that stochastic dots print with a thinner ink film. Hmmm, does a stochastic dot on the plate have a thinner ink receptive coating?
John Lind
Cranberry Township, PA
724-776-4718

 

[Deleted member 16349]

Brian:
As for stochastic, there is that oft stated idea that stochastic dots print with a thinner ink film. Hmmm, does a stochastic dot on the plate have a thinner ink receptive coating?
John Lind
Cranberry Township, PA
724-776-4718

John,

The subject of how much ink a very small dot would take was discussed in my 1997 TAGA paper. The discussion was general and not specifically about FM screening but it is related.

The logic goes as follows. If one has two surfaces such as the image area of a plate and form roller with ink between them, it is reasonable to expect that the ink film will split relatively in the middle of the ink film. This condition would be for printing a solid.

Sometimes it has been stated that printing dots of a screen is like printing small solids. This is not quite true since the fluid flow conditions in the region about the dot would be different from the fluid flow conditions between two surfaces when printing a solid.

When one splits an ink film when printing a solid, there normally would not be much lateral flow of ink. This means no flow of ink parallel to the split line. When printing dots, lateral flow is possible and so is uneven flow in the machine direction and the dot might take more or less ink per surface area than a solid. In the TAGA paper I suggested that it might be more for dots that were relatively large such as in midtones.

Very small dots on the other hand would tend to take less ink per area than a solid. This suggestion was based on the idea that as one got to very small image areas, the pulling power (suction) of separating the surfaces would not be enough to take a lot of ink. One way to think about it is to think about what happens when you touch the surface of ink, in a pail, with the tip of your finger. As you lift up the finger, only a little bit of ink comes out of the pail. Take an even smaller surface and touch the ink and lift. Probably even less ink per area will come out. As you go to smaller and smaller contact areas, less ink per area will be transfered.

It is not the receptability of the surface that is different but one also must consider the fluid mechanics of the action and geometry of the particular process of separation.

Since the very small dot takes ink in a way that is more independent of the ink film thinkness in the nip between the plate and form rollerthan would be the case for larger dots, this tends to make FM print more consistently than AM when SID varies.

 

[Green Printer]

Brian

Change your mylar packing under the blanket to paper. I would use 7 sheets of .003 Paper. Spray a little oil on the sheets (vegtable spray wiil work). Every space between the sheets has a potential vector force that can disipate some of rotational irregularities. The mylar will relfect the irregularities back into blanket and thusly onto the plate (abbrasive action). The mylar is a solid material and does not give.

 

[Green Printer]

Brian does the wearing action start at the gear side of the press and work its way across?

 

[jlind]

Erik:
That was an excellent discussion about ink splitting to the small dots. Now, back to plate wear, do you think the developer brushes leave a thinner dot of emulsion on the plate, more peripheral chemical attack of the stochastic dots, and thus more prone to plate wear? Or, are they all sharp stair stepped features like the old Square Spot PR campaign? I remember running plate wear experiments or run length evaluations, and you always look for highlight dot disappearance before you see any change in a large solid.
John Lind
Cranberry Township, PA
724-776-4718

 

[Deleted member 16349]

Erik:
Now, back to plate wear, do you think the developer brushes leave a thinner dot of emulsion on the plate, more peripheral chemical attack of the stochastic dots, and thus more prone to plate wear? Or, are they all sharp stair stepped features like the old Square Spot PR campaign? I remember running plate wear experiments or run length evaluations, and you always look for highlight dot disappearance before you see any change in a large solid.
John Lind
Cranberry Township, PA
724-776-4718

John,

I have not really done any work on plate wear, so I can not say much. What I can say is what I would look for and think about if I was working on that problem.

I am not so chemically knowledgeable but I would try to get information on what chemicals the image area material has low resistance to. List chemicals used in general in the plateroom and at the press. Review issues related to positive or negative plates and levels of exposure. Research the issue in texts, on the Internet and from pressmen and suppliers. Basically looking for any kind of background info to see if some kind of relationship pops up.

I would also look at the plate and try to think of a mechanism for wear.

Wear could be due to harsh abrasion of a normal image surface material or lighter normal abrasion of a weakened surface material. (Can the relative hardness of the material be measured?) Is the emusion being attacked or is the bond of the emusion to the plate substate being attacked.

I would ask myself, why the dots would wear faster than the solids, if that is the case. Well let's look.

If one thinks of a point in a solid image area we see that it is surrounded by other solid image area. The point has support on all sides.
Looking at a point on a dot and particularly at the edge of a dot, we see that the point is in contact with other image area material only partly around itself.

If one had mechanical abrasive or chemical attack, it is reasonable to expect that the points of image area material at the edges of the image will fail first due to less support from material around it. I don't know but I would expect that dots have the same emulsion thickness as solids.

The Square Spot does bring back memories. I think it is very possible that the edges of the dot made with the Square Spot could be close to the same hardness as the solid since the spot is tighter in dimension and the thermal cure kicks over due to a temperature threshold. The visible light curing method would tend to have a gradient of exposure at the edge and therefore problably a gradient of hardness. These might affect wear.

If as we have discussed, the wear is first and mostly at the edges of dots, then small dots would show up as having the appearance of faster wear than larger dots due to the ratio of circumference length to dot area, or something like that. With an FM screen, if the first bit to wear is the whole dot, then that shows up fast.

Sorry I have no in depth knowledge of the problem. Just conjecture.

 

[Brian Gibson]

Brian does the wearing action start at the gear side of the press and work its way across?

Seems to show up in the same spot on all four presses.
Shows on the black unit first but will eventually show up on all units.
It wears from the side to side direction. Not Lead to tail.
Doesn't seem to start more on the gear side as opposed to the operator side.

I'll check into the paper packing suggestion.

Thanks,
Brian

 

[Brian Gibson]

We have decided to go back to our original fountain solution (Nensco Liquid Gold, nuetral)
Should have it in the system this week so we should see results over the next couple weeks.
We did try the Fuji LHPL long run version of the LHPJ. It wore out just as fast as the LHPJ.
I'll keep you posted.
Thanks to everyone who has responded. Very interesting information.
Please have a safe week.
Brian

 

[Robert L.]

No one mentioned that the problem might be related to the CtP imager. Has the exposure been checked? I noticed you have 2 machines; is the problem possibly from just one? Lasers tend to degrade over time and need re-calibration. Since your problem seems to have gradually appeared over time, I'd recommend checking the exposure on several areas of the plate, particularly areas where the breakdown occurs.

 

[Darlek]

Web plate wear

Web plate wear

I think it is your ink. The compnay I work for that produces newspapers also uses Flint ink. We had had plate wear appear on all colours and after checking roller settings and trying different plates blankets etc, we suspected it might be the ink. We had different forumulas of thier ink delivered and the black wear went. After this we also had a second trial of Cyan ink delivered and the plate wear went on the Cyan. The only wear now is with the Magenta and we have another trial Magenta to try this week. We asked for ink with reduced solid matter and more oil in the ink.
I was told by another rep that to save costs Flint has reduced the amount of milling with there inks and also reduced the amount of oil in their inks. This was to save them money.(Flint are managed by a venture capitalist company) The oil is not only a vehicle to carry the pigments but also acts as a lubricant. I know this is hard to believe as I had my doubts to but without changing anythink else the wear has gone exept for the Magenta. Another way to prove it is to contact Sun chemicals and ask for a trial.

 

[jlind]

I think you are right, Darlek! Excellent post. And a printer should be able to prove this with a Hegman grind gauge.
John Lind
Cranberry Township, PA
724-776-4718

 

[Ronnie]

Hi, I saw your post on printplanet.com. I have 13 years on a goss urbanite and we also used to have problems like that. First things first, you need to make sure your iron to iron is set, plate to blanket and blanket to blanket. look where the plate is wearing and mark that area on the plate cylinder with the plate off. Inch the unit until that mark lines up with the blanket cylinder and check that spot. If its good then check the forms. most of the time the dampmer form is set to tight. Or your ink forms are pounding the plates. I can tell you this is a press issue. not plates. You might need to have someone come in and do a bearing load tests on those units 10 and 13 sides. One more thing, your water system should be an R.O. system.

 

[printsha]

Hi Brian Gibson,
I am facing the same wear out problem & did everything from changing Blankets, Plates, ink suppliers, different plates, fount change,roller change, did entire press setting but still facing image wear problem from side to side basically in solids.I will be thankfull to you if you can provide me some valueable information.
Thanks

 

[printsha]

Mr Gibson,

Are you still in the forum?
Does your image wear problem shorted out?
Please help!!!
Thanks

 

[ianthompson]

hey guys,

just been reading your thoughts on plate wear ,and none of you have have brougt paper to the for front the paper you guys are using whats the calcuim carbonate like in the tech sheets please check.
the calcuim carbonate causes the calcuim compounds leach, build up, and overwhelm the printing system, causing plate scumming or plate blinding with the blanket and roller glaze impleding the transfer of ink and necessitating frequent but inafective wash ups.

please look into the papers as much as anything else.thanks ian thompson

 

[rstirpe]

plate wear

plate wear

is this happening just past the 1/2 half fold on your community