Plate image wear on press

[QualityPrint]

We have two Komori 40" presses and are having problems on large run job with the image on the plates wearing off. We are a two shift operation and it only happens when 1st shift has to finish or continue on a job from second shift. I would like to find some best practices for saving/ gumming plates overnight. Currently we use Prisco FSG storage gum on the clean plate but sometimes this doesn't even work. Our plates are rated for 250k impressions or better and we don't even get half of that but I think it is because of the way we save them.
thanks in advance for your help

 

[Cornishpastythighs]

Some suggestions, Storage gum might be a bit much for just overnight protection, try using a product called FPC (Finisher-Preserver-Cleaner) its a very mild gum for short term protection. Gumming procedure I have always followed is 1. soak plate with clean water on Sponge. 2. Use wash to remove ink 3. Soak plate again with clean water to remove solvent. 4. Apply FPC Gum with clean damp sponge and then lightly buff dry.
Maybe your solvent wash is too strong and contributing to the premature plate image wear and of course you should always make sure ink Form rollers are not set too heavy on the plates and that you are printing with the correct Plate/Blanket squeeze. .004" to .006" for Compressible blankets.
Good luck

 

[jonprintz]

If the image is wearing off of your plates then perhaps you have a plate making problem? Are the plates baked after imaging to harden the image? If so, check this system for needed maintenance and get your plate supplier involved. Getting half life out of the plates isn't acceptable for you nor will it be for your supplier.

I agree with the what cpt posted also.

 

[QualityPrint]

One of our guys uses a method where after the unit is washed up he applies the ink forms and water form to the clean plate and lets it run for a minute or so. Then he rinses the unit again to clean out whatever came off of the plate. Using this method we still get plate wear. So I'm thinking that the fountain solution on the plate is eating away at the image.

I think our pressman has adopted this way because it is much easier than washing all eight or six plates individually...

We do not bake our plates but our manufacturer says that we should get at least 250k out of them even without baking them.



CornishPastyThighs: Is that why you wash the plate with water to clean off the fountain solution first? Do you think that leaving excess fountain solution on the plate can cause this wear? The wear happens on the smallest percentages of coverage first...

 

[Cornishpastythighs]

I was always taught water first and water/gum last. Leaving fountain solution on the plates could I suppose be 'softening' the image but so could your roller wash. Plates nowdays are far more sturdy than back in the day and you should not be getting plate wear after 250K on a good quality plate providing all your press settings are within specs. However if you are not experiencing plate wear during the run and only get it after starting up from an overnight shutdown you might want to try having the supplier bake some plates for you just for sh-ts and giggles. Is the issue on both Komoris and all print units, any colours/print units worse than others. Time for some detective work.
Good luck

 

[seejay]

if your concerned about your fount solution, try a drop test.
1. Take an imaged plate and clean off gum.
2. take some drops of fount and leave it to sit on the plate (on an image area) for a couple of minutes
3. wipe off the fount solution and then check if it has damaged/ate away at the emulsion

This should identify if the fount is responsible for the plate wear.

 

[loopyg66]

talk to your plate manufacturer and see what they recommend. with today's plates, this shouldn't be an issue. I work in a one shift shop and have regularly washed up and not gummed the plates and came in the next day and continued on with no problems at all.

normally, plates that are suppose to get the kind of mileage you are looking for need to be baked. there are things on press that can cause premature wear as well, such as too much squeeze between plate and blanket, fountain solution, dirt on blankets (spray powder, paper coating, etc), wrong solvent.

most plate manufacturers will have a list of approved chemistry for their plates..... again, check with them.

I don't believe it's your gumming process......it's most likely from somewhere/something else.

 

[QualityPrint]

LoopyG... I think your right... I looked at some trends today and noticed that it happens mostly on our 1st and 2nd unit on our 8 color... It also happens more frequently on silk stocks so I am thinking that paper dust buildup gets on the blankets and wears out the plates.
We have an aerator/jogger but maybe we should look into a sheet cleaner?

 

[Alois Senefelder]

Matt Coated

Matt Coated

Hello "Q"

Basically, sound advice from previous contributers, the addition of a Sheet Cleaner is good but remember that printing on Matt/Silk Coated paper is like printing on Sandpaper !.

Whatever the Plate Manufacturers claim --- Bake the plates for 50,000 + runs ---

SAVES PRESS DOWNTIME

Regards, Alois

PDF - I hope you find it of Interest and Value

 

[graficworx]

Sounds like your 1st and 2nd units are taking the brunt of the paper. As previously suggested, paper dust is an abrasive, and likes to stick to wet blankets where it gets transferred to the plates. If your have lots of grit in the ink/water train, when you start up the 2nd shift, before the water has a chance to totally come up you may be "sanding" the plates. If this is a consistent problem on a certain type of paper, maybe try spraying a little fountain solution on the plates immediately prior to re-starting the press. The little extra water may give you enough time for the water to come up, and not let the blanket act like a sanding disk against the plate.

 

[turbotom1052]

considering that its happening mostly in the first couple of units id be looking at the possibility of a calcium buildup in your ink rollers. calcium in the rollers will often prevent the plates receptivity to ink. Are your guys doing regular calcium rinses? if not id suggest you begin. it may take a few repeated calcium rinses just to get rid of a high buildup then once all calcium is removed you might want to get on a regular schedule to clean . Im thinkin at least once a week should suffice unless you run alot of uncoated stocks in which you may need to do it twice a week. any commerially available alkaline rinse should work but if unavailable at the moment a little white vinegar will work.

 

[graficworx]

considering that its happening mostly in the first couple of units id be looking at the possibility of a calcium buildup in your ink rollers. calcium in the rollers will often prevent the plates receptivity to ink. Are your guys doing regular calcium rinses? if not id suggest you begin. it may take a few repeated calcium rinses just to get rid of a high buildup then once all calcium is removed you might want to get on a regular schedule to clean . Im thinkin at least once a week should suffice unless you run alot of uncoated stocks in which you may need to do it twice a week. any commerially available alkaline rinse should work but if unavailable at the moment a little white vinegar will work.

What would be the source of the calcium buildup? I've never heard of that before, but I haven't been doing this long either.

 

[QualityPrint]

Calcium would come from the paper... These are all very interesting suggestions... We are in the process of tracking the way we are doing things i.e. calcium fixes, blanket to plate pressures, and we are going to start hitting the plates with fountain solution before printing especially on silk or matte stocks. I'll keep you guys posted... any more ideas are always welcomed...
thanks again
Q

 

[turbotom1052]

calcium carbonate does in fact come from paper. These days industry trends in paper manufacturing have shown higher levels of calcium carbonate present in todays paper. Ive heard that it has to do with a cheaper way of manufacturing the paper. Ive seen it happen more so with uncoated papers but coated stocks are not immune to it. Have you noticed when running uncoated papers a tendancy for the first couple of blankets to build up a chaulky residue on the blankets that is very stubborn in cleaning off? anything that gets on the blanket will migrate to the rollers via the plate. Contamination of the fountain solution will follow. The buildup in the rollers will eventually lead to poor ink transfer and eventually blinding of the plates. A pretty good indicator of a buildup in your rollers will show itself as circumfrential bands of water when visually inspecting the running plate. This calcium carbonate buildup issue was very prevalent about 10 or 15 years ago when the trend in paper manufacturing seemed to change. Plate manufacurers and chemistry manufacurers both responded with changes in their products to combat this very issue. the final word on this seemed to come down to pressroom personel adopting changes in washup routines to include lots of water during roller washes and regular alkaline rinses with products designed to "douche" rollers clean of the offending deposits. the suggestions mentioned goes on the assumption that your press is mechanicaly sound with the proper packings required to print. As someone else mentioned your total squeeze between plate and blanket should not exceed .005" when running a compressible blanket. More than that could adversely effect plate life. If after a few calcium rinses the problem persists i would recomend getting the suppliers involved in helping to find the cause. not to sound like an ass but the very fact youve never heard of this well documented issue leads me to believe that perhaps your pressroom is a little lacking in experience.

 

[FujiFrank]

You may also want to consult with your fountain solution provider to be sure that you have a calcium fighting agent contained within it.

Many times when you do have a bad calcium problem it will show up in the magenta unit as blinding because magenta ink contains a high degree of calcium. The Cyan does not, but black does. So in the field we can see actual calcium blinding in the Magenta and Black units.

Also if it is actual calcium blinding the dots will still be visible on the plate but they will reject ink. Sometimes if you clean the plate with vinegar it will then come back to life for a while.

If you are actually loosing dots this is different than calcium blinding.

If anyone has experience with actual plate wear from calcium I would love to hear about that.

Sincerely,

 

[Kaoticor]

Quick side point: Double check the thickness of your blankets on those units if you get a chance. Dont pay attention to the measurement they stamp on there, measure it for yourself. I know it sounds basic, but the basics are also what get us the most.

Although anything can affect almost anything in printing, I would be inclined to think that it is probably not the way you are storing them. The other comments have some good ideas to think about.

 

[BeauchampT]

Another sidepoint: Although your plate supplier says 250k, what sort of resistance to wear? chemical? Wonderful, you can pour some acid and solvent on your plate for 250k impresions, but it has nothing to do with the mechanical wear.

As Kaoticor said, if your squeeze is to high - mechanical wear; if you have abrasive paper debris - mechanical wear; if your ink is poorly ground - mechanical wear. Chemical wear resistance rated to 250k does you zero good in those situations.

As said in a previous comment, baking is a safe solution - you get both chemical AND mechanical resistance to wear.